Deliverable D3.2: Measurement protocols · Deliverable D3.2: Measurement protocols WP3: Cable and materials characterisations Grant Agreement number: 755183 NFRP-2016-2017-1 Euratom

Deliverable D3.2: Measurement protocols

WP3: Cable and materials characterisations

Grant Agreement number: 755183 NFRP-2016-2017-1

Euratom programme Research and Innovation Action

Start date of project: 1st September 2017 Duration: 54 months

Lead beneficiary of this deliverable: ENSAM

Dissemination Level: Public Document type: Report

Due date of deliverable: 31/07/2018 Actual submission date: 11/01/2019

Author(s) of this deliverable: ENSAM, IRSN, UNIBO, UJV, VTT, CEA, AMU, IZFP, INCT and NEXANS

TMC-TMC-D3_2-MEASUREMENT_protocols.docx

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Public Copyright TeaM Cables consortium Page 2 / 121

Table of Contents

Glossary ................................................................................................................................................... 7

1 Executive Summary ......................................................................................................................... 9

2 Introduction ................................................................................................................................... 10

3 Dosimetry measurements ............................................................................................................. 11

Round robin test protocol ..................................................................................................... 11

Results ................................................................................................................................... 11

4 Electrical measurement protocol .................................................................................................. 12

Protocol for experimental measurements ............................................................................ 12

4.1.1 Electrical breakdown measurement protocol ............................................................... 12

4.1.2 Dielectric spectroscopy measurement protocol ........................................................... 12

4.1.3 Charging/Discharging currents (CDC) measurement protocol ...................................... 15

4.1.4 Insulation resistance measurement protocol ............................................................... 17

4.1.5 Space charge measurements protocol using the Pulse Electro Acoustic (PEA) method 17

Round robin test results ........................................................................................................ 18

5 FTIR measurement protocol .......................................................................................................... 19

Introduction ........................................................................................................................... 19

Participants ............................................................................................................................ 20

Protocol for FTIR measurements ........................................................................................... 20


References ............................................................................................................................. 20

6 DSC measurement protocol .......................................................................................................... 22

Introduction ........................................................................................................................... 22

Participants ............................................................................................................................ 22

DSC measurement protocol .................................................................................................. 22

DSC results obtained for unaged Model 1 ............................................................................ 23

References ............................................................................................................................. 24

7 OIT measurement protocol ........................................................................................................... 26

Introduction ........................................................................................................................... 26

Participants ............................................................................................................................ 26

Protocol for OIT measurements ............................................................................................ 26


8 EaB measurement protocol ........................................................................................................... 29

Participants ............................................................................................................................ 29

Standards and procedures .................................................................................................... 29


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Test materials ........................................................................................................................ 29

Sample preparation ............................................................................................................... 30

Sample conditioning .............................................................................................................. 32

Test parameters .................................................................................................................... 33

Test environment .................................................................................................................. 33

Results ................................................................................................................................... 34

Acceptance criteria ................................................................................................................ 34


9 EPR measurement protocol........................................................................................................... 36

Introduction ........................................................................................................................... 36

Participants ............................................................................................................................ 37

Preparation of samples ......................................................................................................... 37

EPR experiments .................................................................................................................... 37

EPR parameters: .................................................................................................................... 38

Documentation and data analysis ......................................................................................... 38


10 Swelling test measurement protocol ........................................................................................ 39

Introduction ........................................................................................................................... 39

Participants ............................................................................................................................ 40

Swelling test protocol ............................................................................................................ 41

Results obtained for unaged Model 1 ................................................................................... 42

References ............................................................................................................................. 44

11 Gas analysis protocol ................................................................................................................. 45

Introduction ........................................................................................................................... 45

Participants ............................................................................................................................ 45

Gas analysis protocol ............................................................................................................. 45

11.3.1 Second-step irradiation conditions ............................................................................... 45

11.3.2 Gas analysis ................................................................................................................... 45

References ............................................................................................................................. 46

12 UV measurement protocol ........................................................................................................ 47

Introduction ........................................................................................................................... 47

Participants ............................................................................................................................ 47

Protocol for UV measurements ............................................................................................. 47

Results obtained for unaged samples ................................................................................... 48

References ............................................................................................................................. 48

13 Indentation measurement protocol .......................................................................................... 49

Introduction ........................................................................................................................... 49


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Participants ............................................................................................................................ 50

Samples preparation ............................................................................................................. 50

Protocol for micro-indentation measurements .................................................................... 51

Results obtained for unaged samples ................................................................................... 51

References ............................................................................................................................. 52

14 THz technique measurement protocol...................................................................................... 53

Introduction ........................................................................................................................... 53

Results of the impedance analyser for unaged samples ....................................................... 53

Calculated permittivities in transmission mode .................................................................... 55

Calculated permittivities in reflection mode ......................................................................... 56

Comparison of permittivities in reflection and transmission mode ..................................... 57

15 Isothermal TGA measurement protocol.................................................................................... 59

Introduction ........................................................................................................................... 59

Participants ............................................................................................................................ 59


Dynamic TGA test .................................................................................................................. 59

Isothermal TGA test ............................................................................................................... 59

Documentation and data analysis ......................................................................................... 60

16 SEM examination protocol ........................................................................................................ 61

Introduction ........................................................................................................................... 61

Participants ............................................................................................................................ 61

Samples preparation ............................................................................................................. 61

Protocol for SEM measurements .......................................................................................... 61

17 DMTA protocol .......................................................................................................................... 63


Measuring protocol ............................................................................................................... 63

Interpreting the results ......................................................................................................... 63

18 Ultrasonic measurement protocol ............................................................................................ 65

19 Conclusion ................................................................................................................................. 66

20 Annex 1: Results of Round Robin Tests on Dosimetry Measurements ..................................... 67

Participants ............................................................................................................................ 67

UJV dosimetry ........................................................................................................................ 67

INCT dosimetry ...................................................................................................................... 69

IRSN dosimetry ...................................................................................................................... 70

Discussion and conclusion ..................................................................................................... 71

20.5.1 Summary of results ........................................................................................................ 71

20.5.2 Discussion ...................................................................................................................... 72


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21 Annex 2: Results of Round Robin Tests on Electrical Measurements ....................................... 73

Participants ............................................................................................................................ 73

Cable samples ........................................................................................................................ 73

Insulation resistance measurement results and discussion .................................................. 73

Capacitance measurement results and discussion ............................................................... 83

Tan delta measurement results and discussion .................................................................... 87

S matrix measurement results and discussion ...................................................................... 90

General conclusion on the electrical measurements ............................................................ 91

22 Annex 3: Results of Round Robin Tests on FTIR Measurements ............................................... 92

Participants ............................................................................................................................ 92

Test materials ........................................................................................................................ 92

Model silane crosslinked PE (Mod1-Tpe-RR-OIT) .................................................................. 92

22.3.1 ATR mode ...................................................................................................................... 92

22.3.2 Transmission mode ....................................................................................................... 93

22.3.3 Peak attribution ............................................................................................................. 93

Twisted-pair cable filled XLPE insulation (TXLF-SCa) ............................................................. 95

22.4.1 ATR mode ..................................................................................................................... 95


Twisted-pair cable EVA/EPDM insulation (EVEP-Sca) ........................................................... 97

22.5.1 ATR mode ...................................................................................................................... 97


General conclusion on the FTIR measurements .................................................................... 98

23 Annex 4: Results of Round Robin Tests on OIT Measurements .............................................. 100

Participants .......................................................................................................................... 100

Test materials ...................................................................................................................... 100

Model silane crosslinked PE (Mod1-Tpe-RR-OIT) ................................................................ 100

23.3.1 Results ......................................................................................................................... 100

23.3.2 Arrhenius plots ............................................................................................................ 102

23.3.3 Discussion .................................................................................................................... 104

One-pair cable filled XLPE insulation (OPTC-SCa-RR-OIT) ................................................... 104

23.4.1 Results ......................................................................................................................... 104

23.4.2 Arrhenius plots ............................................................................................................ 106

23.4.3 Discussion .................................................................................................................... 108

Twisted-pair cable unfilled XLPE insulation (TXLN-SCa-RR-OIT) .......................................... 108

23.5.1 Results ......................................................................................................................... 108

23.5.2 Arrhenius plots ............................................................................................................ 110

23.5.3 Discussion .................................................................................................................... 112


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Twisted-pair cable filled XLPE insulation (TXLF-SCa-RR-OIT) ............................................... 113

23.6.1 Results ......................................................................................................................... 113

23.6.2 Arrhenius plots ............................................................................................................ 114

23.6.3 Discussion .................................................................................................................... 116

General conclusion on the OIT measurements ................................................................... 116

References ........................................................................................................................... 119

24 Annex 5: Results of Round Robin Tests on EaB Measurements .............................................. 120

Round robin test results ...................................................................................................... 120

Test materials ...................................................................................................................... 120

Results ................................................................................................................................. 120

General conclusion on the EaB measurements .................................................................. 121


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Glossary

Abbreviation/ acronym Full name

AC Alternative Current

ATR Attenuated Total Reflectance

CDC Charging/Discharging Currents

CW Continuous Wave

DC Direct Current

DMTA Dynamic Mechanical Thermal Analysis

DS Dielectric Spectroscopy

DSC Differential Scanning Calorimetry

Ea Activation Energy (J.mol-1)

EaB Elongation at Break

EPR Electron Paramagnetic Resonance

EPRS Electron Paramagnetic Resonance Spectroscopy

FFT Fourier Fast Transform

FTIR Fourier-Transform Infrared

GUI Graphical User Interface

IR Infrared

N/A Not Applicable (data not available)

OIT Oxidation Induction Time

PB Partial Breakdown

PCA Principal Component Analysis

PEA Pulse Electro Acoustic

R perfect gas constant (8.314 J.mol-1.K-1)

SEM Scanning Electron Microscopy

st.dev. standard deviation

T Temperature (K)

TC TeaM Cables

TGA Thermogravimetric analysis


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Abbreviation/ acronym Full name

uns unsuitable material

UV Ultraviolet


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1 Executive Summary

This document presents the main characterisation methods and the measurement protocols that will be routinely and jointly performed by the different laboratory partners throughout the course of the TeaM Cables project. A both multi-scale and multi-technical approach was chosen for elucidating the ageing mechanisms operating in the polymeric materials of electrical cables, but also for understanding their consequences on functional properties. It consists in analysing, at different pertinent structural scales with a series of complementary laboratory techniques, all changes occurring in the materials under study. The changes in chemical structure will be evidenced by OIT measurement, FTIR and UV spectroscopy, EPR, TGA and gas analysis. The changes in the macromolecular network and crystalline morphology will be evidenced by swelling test, DSC and DMTA. The consequences on mechanical properties will be evidenced by micro-indentation and EaB measurement. And finally, the consequences on dielectric properties will be evidenced by electrical measurements and THz spectroscopy. All these experimental results will be used to check the validity of the multi-scale modelling tool that will be developed in the TeaM Cables project for predicting the lifetime of electric cables in service, but also to identify its different parameters.

At this stage of the TeaM Cables project, the measurement protocols were only developed for virgin materials (i.e. before ageing). That is the reason why it is not excluded that they will be re-adjusted or modified for aged materials. All these protocols are based on standard references (when they exist), state of the art or, simply, the know-how of the partner laboratories. The validity of some of them (in particular OIT, FTIR, EaB and electrical measurements) was carefully checked by performing “Round Robin Tests”. The comparison and discussion of the experimental results obtained with the same technique on the same materials, but by several laboratory partners, are provided in the different appendixes of this deliverable. This specific exercise allowed to identify measurement gaps between several laboratory partners and to propose, when possible, ways of improvement of the characterisation methods and measurement protocols. Thereafter, all these experimental results will be integrated into a database for statistical analysis in order to help the identification of ageing markers, but also to define the uncertainties and reproducibility of the experimental techniques.


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2 Introduction

This document presents the main characterisation methods and the measurement protocols that will be routinely and jointly performed by the different laboratory partners throughout the course of the TeaM Cables project. When applicable, deviations between the measurement protocols and existing standard protocols are evidenced and discussed. For several protocols, the first step of the TeaM Cables project consisted in performing a series of “Round Robin Tests” between the different partner laboratories who will use the same characterisation methods. The objective was to check eventual measurement gaps between several partner laboratories doing the same characterisation on the same samples and to propose, when possible, ways of improvement of the characterisation methods and measurement protocols. The corresponding experimental results obtained during this specific exercise are provided in the appendices of this deliverable. Finally, it should be noted that the virgin materials which have been selected for these “Round Robin Tests” will then be submitted to accelerated thermal and radiochemical ageing. As a consequence, the same measurement protocols developed in this document will be tentatively used for unaged samples, and re-adjusted or modified if necessary.


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3 Dosimetry measurements

Dosimetry is a specific case. Of course, it is not a measurement technique to be used for characterising the cable materials, but it was necessary to check that the dosimetry measurements by the three laboratories performing irradiations (IRSN/France, UJV/Czech Republic and INCT/Poland) were consistent.

Round robin test protocol

To compare the different dosimetry systems, UJV (Czech Republic) and INCT (Poland) sent their dosimeters to irradiation to IRSN (France). Subsequently, the dosimeters of each laboratory were irradiated at three various doses (between 1 and 80 kGy) at ambient temperature. IRSN indicated the doses measured from their dosimeters (PMMA from HARWELL Dosimeters). Other dosimeters were sent back for evaluation to ICNT and UJV. INCT and UJV evaluated the dose of their irradiated dosimeters and sent their results individually to IRSN.

Results

The results of the round robin tests on these dosimetry measurements are provided in Annex 1. After a first series of measurements which was not very conclusive due to the localization of the dosimeters (and so to the actual dose rate at each dosimeter location) which was not precise enough, a second series of measurements showed standard deviations between the different measures below 8%, which is very acceptable for dosimetry measurements.


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4 Electrical measurement protocol

Protocol for experimental measurements

4.1.1 Electrical breakdown measurement protocol

Failure of electrical insulation properties of insulating materials is known as “breakdown”. There are two kinds of breakdown:

• Global breakdown: it causes the complete failure of the electrical insulation between two

electrodes.

• Local breakdown: it causes the failure of the insulating properties of the material in a selected

area. It is also called “Partial Breakdown” (PB).

Inside the TeaM Cables project only the global breakdown is analysed.

It is worth noting that the dielectric strength of an insulating material varies with: the thickness of the material, area and geometry of the electrodes. Measurement is done in, at least, five different points of the specimen.

To do so, a BAUR DPA 75C with spherical electrodes has been used (see Figure below).

Specifications:

1. Test voltages from 0 to 75 kV rms

2. Voltage rate adjustable 0.5 – 10 kV/s

3. Accuracy 0 – 75 kV ± 1kV

4. Resolution 0.1 kV

5. Switch-off time <10μs

Samples are placed between the electrodes inside a liquid dielectric and a progressive AC 50Hz voltage at a uniform rate of 1.5 kV/s from zero is applied until breakdown. This rate is set according to the standard ASTM D149 - 97a (2004) which states: “in establishing a rate initially in order for it to be included in a new specification, select a rate that, for a given set of specimens, will give an average time to breakdown of between 10 and 20 s”.

In the end a Weibull distribution model is used to analyse lifetime statistics, according to IEC 62539-2007 standard. From this analysis, two parameters are evaluated:

• Alpha parameter: scale parameter providing the Breakdown Voltage

• Beta parameter: slope parameter

4.1.2 Dielectric spectroscopy measurement protocol

Dielectric spectroscopy (DS, sometimes called impedance spectroscopy) measures the dielectric response of a medium as a function of frequency. It is based on the interaction of an external field with the electric dipole moment of the specimen, i.e. electrical polarization.


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This technique measures the impedance of a system over a range of frequencies, and therefore the frequency response of the system.

This experimental setup allows the evaluation of:

• Capacitance

• Dissipation factor (tan δ)

• Complex permittivity (ε’ and ε’’)

in the frequency range between 10-2 -106 Hz.

The measurement principle is shown in the following figure.

This instrument consists of two major components:

• a frequency response analyser with a sine wave and DC-bias generator and two AC voltage

input channels. Each input channel measures the AC voltage amplitude of an applied sine

wave. In addition, the phase shift between the sine waves applied to both inputs is detected.

In particular, each channel measures the amplitude and phase angle of the harmonic base

wave component of a signal applied to the input. The harmonic base wave component is

measured at the frequency of the of the AC sine wave generator. Most other signal

components are suppressed. In addition, higher harmonics may be measured.

• a dielectric (or impedance) converter with a wide dynamic range current-to-voltage converter

and a set of precision reference capacitors.

A voltage V with fixed frequency ω/2π is applied to the sample capacitor. V causes a current I at the

same frequency in the sample. In addition, there will generally be a phase shift between current and

voltage describe by the phase angle ϕ. δ angle is defined as follows:

𝛿 = 90° − φ

WinDETA software was used as a GUI for the described test setup. It requires as input data the

geometry of the sample as reported in the following figure.


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The sample material (flat specimen) is mounted in a sample cell between two electrodes forming a

sample capacitor. Due to roughness of the surface, specimens are silver-metallized through a cold

plasma spattering system in order to enhance the conduction between the electrode and the

specimen.

Input data needed:

• Diameter;

• Thickness.

For cable testing, the inner conductor is connected to the voltage supplier and the low voltage

electrode to a wire mesh surrounding the cable, which provides the signal.

For coaxial cable specimens the following formula is used to evaluate the equivalent diameter:

𝐷𝑒𝑞 = √𝑑8𝐿

ln (𝑅2

𝑅1⁄ )

Where: d is the thickness of the insulation

L is the length of the metallic mesh

R1 and R2 are the inner and outer radius of the electrical insulation, respectively.

For twisted pair cables a FEM simulation is needed to evaluate the correspondent vacuum capacitance

C0 of the considered geometry. Once calculated, it can be put inside the Sample specification window.


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Relaxation peaks shift as a function of temperature. That is the reason why different temperatures

are set during analyses:

• -100°C

• -50°C

• 0°C

• 25°C

• 50°C

• 75°C

• 100°C

These values of temperature are used only for flat specimens. For cables, test temperature is set at

50°C. The test voltage is set at 3 Vrms, which is the maximum voltage available from the instrument.

Each measurement takes about 30 minutes per each temperature. As output of the system a plot of

the desired quantity as a function of frequency is recorded.

4.1.3 Charging/Discharging currents (CDC) measurement protocol

Standard: ASTM D 257-07 “DC Resistance or Conductance of Insulating Materials”

The CDC measurement procedure is made up of two phases:

1. Polarization phase: the DC voltage is switched on and the polarization process begins. An

electrometer acquires the measured current (usually nA) as a function of time;

2. Depolarization phase: the DC voltage is switched off and the specimen is short-circuited. The

depolarization current is registered until it reaches zero A.

Electrometer

DC voltage generator


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For flat specimens a proper experimental cell is used to contact the sample. A particular metallization is needed in order to avoid the contribution of leakage currents (Figure below by ASTM standard protocol).

For cable specimens the insulation resistance is measured between conductors (with high voltage applied) and shielding (grounded).

Using the Fourier Fast Transform (FFT), the complex electric susceptibility can be derived from this measurement.

The response of the system in the time domain is obtained directly from the depolarization current:

𝑔(𝑡) = −𝐽𝑑(𝑡)

휀0𝐸

Where Jd is the measured depolarization current caused by the polar species returning to the casual distribution.

ε0 is the permittivity in vacuum

E is the electric field

Applying the FFT to g(t), the response in the frequency domain (complex susceptibility) χ(ω) can be derived through:

𝜒(𝜔) = 𝜒′(𝜔) − 𝑗𝜒′′(𝜔)

= ∫ 𝑔(𝑡) exp(−𝑗𝜔𝑡) 𝑑𝑡 =+∞

0

∫ 𝑔(𝑡) cos(𝜔𝑡) 𝑑𝑡 − 𝑗 ∫ 𝑔(𝑡) sin(𝜔𝑡) 𝑑𝑡+∞

0

+∞

0

This expression is related to the complex permittivity through the following formula:

𝜒′ =휀′ − 휀0

휀0

𝜒′′ =휀′′

휀0

This measurement protocol allows the evaluation of the complex permittivity in a lower frequency range (up to 1 Hz). However, it is worth noting that obtained ε’ values are smaller than the real ones. That is because information can be acquired only on the peak related to the interfacial polarization. Dipolar polarization contribution disappears as soon as the DC voltage is turned off.


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The tests reported are performed at the electric field of 10 kV/mm and room temperature.

4.1.4 Insulation resistance measurement protocol

Standard: the same as for CDC measurements.

The experimental setup is the same as above.

DC voltage is set at 100, 500 and 1000 Volts (depending on the kind of cable tested as requested).

During the polarization phase current values (in A) are measured at 30, 60, 300 secs as requested by the TeaM Cables project.

In the end Rinsul is obtained as follows:

𝑅𝑖𝑛𝑠𝑢𝑙(Ω) =𝑉𝑜𝑙𝑡𝑎𝑔𝑒 (𝑉)

𝐶𝑢𝑟𝑟𝑒𝑛𝑡 (𝐴)

4.1.5 Space charge measurements protocol using the Pulse Electro Acoustic (PEA) method

The PEA method is a non-destructive technique for profiling space charge accumulation in polymeric materials. A sequence of high-voltage pulses of very short time length (5-30 ns) is applied to an insulation specimen interposed between two electrodes. Each pulse produces an electric force displacing internal charges and generating pulsed acoustic pressure waves in correspondence of each charge layer in excess with respect to neutrality. The resultant pressure pulse is detected by a piezoelectric transducer, so that the charge distribution in the specimen under test can be obtained from the output voltage of the transducer. The output signal is then amplified and visualized by a digital oscilloscope. The analysis of space-charge profiles is restricted to one dimension: this assumption imposes to consider that space charge density, electric field distribution and acoustic wave propagation can vary only along the specimen thickness (z-coordinate).

A sketch of the PEA system is reported in the following figure:

Sample preparation: the PEA setup is made of two electrodes, sample is put between these two electrodes. Usually, no surface treatment is needed, however it can be required to treat the surface with silicon oil in order to facilitate the signal transmission.


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The polarization voltage and the pulse probe voltage are applied to the top electrode while the bottom electrode is used as a detention electrode.

A quantity associated with the space charge accumulation in the insulation bulk is the absolute stored charge density, qS, which represents the absolute value of the charge accumulated in the bulk at a chosen depolarization time. It can be obtained from the space charge profiles after polarization at field E applying the following equation:

𝑞𝑠(𝐸, 𝑡𝑑) =1

𝑙∫ |𝑞(𝑥, 𝐸, 𝑡𝑑)|𝑑𝑥

𝑙

0

where l is insulation thickness and td is the depolarization time, q(x,E,td) is the space charge profile detected at time td. The maximum absolute stored charge density, qSM is evaluated at the beginning of depolarization (td = 2 s).

In order to investigate the charge dynamic, the trap-controlled mobility, μ, is estimated from depolarization characteristics qS(E,td) with td in the range 0-3600 s, according to the following simple, but approximate, expression:

𝜇 =2휀

𝑞𝑠2 ∙

𝑑𝑞𝑠

𝑑𝑡

where ε is the electric permittivity of the insulating material.

Test conditions are: E=10kV/mm, T=25°C, Polarization time = 3600 s, Depolarization time: 3600 s.

For each test, space charge patterns and a depolarization curve, reporting qS(E,td) in relative value of qsM, are shown. The scale reported on the right-hand side of the patterns can vary within two possible ranges [-2, +2] C/m3 and [-5, +5] C/m3.

Round robin test results

These experimental measurements were tested through the round robin test exercise between UNIBO/Italy and UJV/Czech Republic. The results of this round robin test exercise are reported in Annex 2. The main conclusions are as follows.

Due to different instrumentations used for measurements, small differences can be appreciated among results of the two laboratories.

Referring to the insulation resistance results, in particular, measured currents are very small and noise-affected in the coaxial cable configuration. This can lead to very difficult resistance value extrapolation since it can easily vary in the very short requested acquisition time.

For the twisted pair configuration, UNIBO and UJV insulation resistance results are close to each other.

Capacitance measurements showed that capacitance is not dependent on both frequency and temperature.

Tan Delta tests showed different behaviours depending on the analysed specimen. In particular, Tan Delta raises with temperature and decreases with frequency in Coaxial cables; on the contrary, in twisted pair configuration, tan delta raises with temperature and decreases with frequency.


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5 FTIR measurement protocol

Introduction

FTIR (Fourier Transform Infrared) spectroscopy is a non-destructive technique based on the interaction of infrared radiation with matter. When light passes through or is reflected from a sample, some is absorbed by the sample and some passes through (it is transmitted). Basically, the amount of light absorbed by the sample is the difference between the incident radiation (I0) and the transmitted radiation (I). This amount of absorbed light can either be expressed in transmittance (T) or in absorbance (A). Transmittance and absorbance can be expressed as follows:

𝐓 =𝐈

𝐈𝟎

𝐀 = − 𝐥𝐨𝐠 (𝐓)

In fact, when radiation interacts with matter, a number of processes can occur (e.g. reflection, absorbance, photochemical reaction, etc.). Absorption of light can cause a transition from an initial energetic state to a higher energy state. The nature of the transitions depends on the energy of the photon but also on the chemical nature of the interacting compound. For instance, in the mid-IR spectral range, which is between 4000 and 400 cm-1, it mostly comprises fundamental vibrations of bound atoms.

Basically, the condition for IR absorption is a net change in molecular dipole moment as it vibrates or rotates. Then, depending on the direction of the vibrational movement, stretching vibration (changes of bond lengths) and deformation vibration (changes of bond angles) can be distinguished. Deformation vibrations may also be divided into several modes, such as bending, twisting, torsion, wagging, and rocking modes. And further subdivision depending on the symmetry of the vibration can be made (e.g. symmetric or asymmetric, in-plane or out-plane).

The vibration frequency of chemical bonds is directly related to the chemical nature of the atoms involved but also on their chemical environment. Furthermore, the intensities of the bands are proportional to the concentration of the chemical functional group involved (using Beer-Lambert law). Hence, FTIR spectroscopy can also be used as a quantitative technique.

In fact, in FTIR spectroscopy, two modes can be used: Reflection mode (e.g. Attenuated Total Reflectance mode) and Transmission mode.

In Transmission mode, the sample is placed in the path of the IR beam, and the resulting transmitted IR signal is recorded by the detector, and the measurements correspond to average values on the whole thickness crossed by the IR beam. Hence, in Transmission mode, as the IR radiation passes through the whole thickness of the sample, the concentration of the chemical functional groups can be determined by measuring the absorbance of their IR band of interest and using the Beer-Lambert law:

𝐀 = 𝛆. 𝐥. 𝐂

Where A is the absorbance, l the IR ray path length (i.e. thickness of the material) in cm, 𝛆 the molar extinction coefficient (in L.mol-1.cm-1), and C the concentration (in mol.L-1) of the considered chemical function. However, it is to be mentioned that the linearity of Beer-Lambert law holds well only for “dilute” samples (i.e. typically for absorbance lower than 0.7 absorbance units) (Chen et al., 2015).

In ATR (Attenuated Total Reflectance) mode, however, the IR radiation is not transmitted through the sample, as in Transmission mode. In ATR mode, the sample is put in contact with an ATR crystal, which is an optically dense crystal having a high refractive index (e.g. Ge, ZnSe or diamond crystal). The IR beam is directed to the ATR crystal at a certain angle, which generates an evanescent wave extending


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beyond the surface of the crystal into the sample, due to a total internal reflection phenomenon. In the regions of the infrared spectrum where the sample absorbs energy, the evanescent wave will be attenuated, and the resultant beam is then used to generate the absorption spectrum of the sample.

The penetration depth of this evanescent wave beyond the crystal surface into the sample is only of a few microns (typically 0.5 to 5 µm), meaning that there must be a sufficient contact between the crystal surface and the sample. Hence, using ATR mode, only the surface of the sample is analysed.

Participants

ENSAM (France. contact: [email protected], [email protected], [email protected] and

[email protected]).

IRSN (France. contact: [email protected] and [email protected]).

Protocol for FTIR measurements

At ENSAM, mid-Infrared spectra are recorded using a Perkin Elmer FTIR Frontier spectrometer. Both ATR and Transmission mode are used to characterise the samples in form of films, while only ATR mode is used for cable insulation. For each sample, three spectra will be recorded on three different days.

In case of ATR mode, the contact between analysed sample and the diamond/ZnSe of the ATR accessory will be ensured by screwing a clamp device, as shown in Figure 5.1. The single beam spectrum of the clean and dry ATR element will be used as background.

In case of Transmission mode, the analysed sample (thin films) will be placed in a specimen holder enabling the sample to be in the IR path, as shown in Figure 5.1.

Figure 5.1: Photos of Perkin Elmer FT-IR Frontier spectrometer using ATR mode (left) and Transmission mode (right)

FTIR spectra will be recorded on absorbance mode. The spectral range scanned will be, in case of Transmission mode, from 4000 to 400 cm-1, and in case of ATR mode, from 4000 to 670 cm-1. The spectral resolution will be of 4 cm-1, and for each spectrum, 16 scans will be accumulated.


These experimental measurements were tested through the round robin test exercise between ENSAM/France and IRSN/France. The results of this round robin test exercise are reported in Annex 3.

References

Chen, Y., Zou, C., Mastalerz, M., Hu, S., Gasaway, C., and Tao, X. (2015). Applications of Micro-Fourier Transform Infrared Spectroscopy (FTIR) in the Geological Sciences—A Review. International Journal of Molecular Sciences 16, 30223–30250.

mailto:[email protected]



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Gauglitz, G., and Vo-Dinh, T. (2006). Handbook of Spectroscopy (John Wiley & Sons).

Minnes, R., Nissinmann, M., Maizels, Y., Gerlitz, G., Katzir, A., and Raichlin, Y. (2017). Using Attenuated Total Reflection–Fourier Transform Infra-Red (ATR-FTIR) spectroscopy to distinguish between melanoma cells with a different metastatic potential. Scientific Reports 7, 4381.


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6 DSC measurement protocol

Introduction

A DSC analysis measures the difference in heat flow (in mW) between a sample and an inert reference during an imposed thermal change, under a controlled atmosphere. DSC analysis gives qualitative and quantitative information on physical and chemical transformations implying heat exchange or variation of heat capacity.

Using DSC, it is thus possible to determine the nature and temperature of exothermic and endothermic chemical reactions (e.g. crosslinking). As they involve heat exchange, physical transitions, such as melting (endothermic process) and crystallization (exothermic process) can also be identified using this technique. It is thus possible to determine the melting and crystallization temperatures, but also to determine the percentage of crystallinity (χc) of the polymer using the following equation:

χc = ΔHm

ΔHm,∞

Where ΔHm is the enthalpy of fusion of the sample (J.g-1), and ΔH∞ is the enthalpy of fusion of a 100% crystalline PE (the commonly used value for ΔH∞ of a PE sample is 290 J.g-1)

Glass transition can also be determined using DSC analysis, as this process implies a variation of heat capacity. On DSC thermograms (heat flow versus temperature), glass transition typically implies a baseline change (sigmoid).

Participants


[email protected])

IRSN (France. contact: [email protected] and [email protected])

DSC measurement protocol

DSC measurements were performed using a TA instrument Differential Scanning Calorimeter Q1000.

Figure 6.1: Photo of DSC Q1000

Squared-form samples of 5 ± 1 mg were used, in closed standard aluminium pans. The reference pan used was an empty closed standard aluminium pan. For optimum heat flux, the highest possible




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contact area between sample and pan bottom should be achieved, e.g. all test samples must sit on the pan bottom.

Figure 6.2: Photo of the inside of the DSC furnace containing the reference pan and the pan containing the sample

The heating/cooling cycle performed for all samples is the following one:

• Equilibration at -80 °C

• Isothermal for 2 min at -80 °C

• Heating rate up to 200 °C: 10 °C/min

• Cooling rate down to -80 °C: 10 °C/min

• Heating rate up to 200 °C: 10 °C/min

DSC experiments are performed under a Nitrogen flow of 50 mL.min-1 (*).

(*) The gas passes through a mass flow controller. The flow rates are then set through the instrument control software and can be controlled during experiments.

Three measurements were performed for each sample.

DSC results obtained for unaged Model 1

Model 1 represents neat silane-crosslinked PE (Silane-XLPE). Figure 6.3 represents the DSC thermograms obtained for Mod1-Tpe, at a heating and cooling rate of 10 °C/min.

Reference (empty pan) Sample


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Figure 6.3: DSC thermograms obtained for Model 1 (neat Si-XLPE)

On the following table (Table 6.1), the results obtained by DSC analysis are compiled (melting and crystallization temperatures and enthalpy, and percentage of crystallinity).

Table 6.1: DSC results for Mod1-Tpe-UnA (neat Si-XLPE)

Tm / Tc (°C) ΔH (J.g-1) χc (%)

1st heating Tm = 114 ± 1 ΔHm = 121 ± 4 42 ± 1

Cooling Tc1 = 101 ± 1

Tc2 = 109 ± 1 ΔHc = 118 ± 1 /

2nd heating Tm1 = 112 ± 1

Tm2 = 118 ± 1 ΔHm = 119 ± 2 41 ± 1

References

Berriot, J., Lequeux, F., Montes, H., and Pernot, H. (2002). Reinforcement of model filled elastomers: experimental and theoretical approach of swelling properties. Polymer 43, 6131–6138.

Celina, M., and George, G.A. (1995). Characterisation and degradation studies of peroxide and silane crosslinked polyethylene. Polymer Degradation and Stability 48, 297–312.

Chen, Y., Zou, C., Mastalerz, M., Hu, S., Gasaway, C., and Tao, X. (2015). Applications of Micro-Fourier Transform Infrared Spectroscopy (FTIR) in the Geological Sciences—A Review. International Journal of Molecular Sciences 16, 30223–30250.


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Flory, P.J., and Rehner, J. (1943). Statistical Mechanics of Cross‐Linked Polymer Networks II. Swelling. The Journal of Chemical Physics 11, 521–526.

Hendra, P.J., Peacock, A.J., and Willis, H.A. (1987). The morphology of linear polyethylenes crosslinked in their melts. The structure of melt crystallized polymers in general. Polymer 28, 705–709.

Iqbal, T., Briscoe, B.J., and Luckham, P.F. (2011). Surface Plasticization of Poly(ether ether ketone). European Polymer Journal 47, 2244–2258.

Kraus, G. (1963). Swelling of filler‐reinforced vulcanizates. Journal of Applied Polymer Science 7, 861–871.

Lorenz, O., and Parks, C.R. (1961). The crosslinking efficiency of some vulcanizing agents in natural rubber. Journal of Polymer Science 50, 299–312.

Möller, K., and Gevert, T. (1996). A solid-state investigation of the desorption/evaporation of hindered phenols from low density polyethylene using FTIR and UV spectroscopy with integrating sphere: The effect of molecular size on the desorption. Journal of Applied Polymer Science 61, 1149–1162.


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7 OIT measurement protocol

Introduction

The principle of OIT measurement is the same as DSC analysis, as it measures the difference in heat flow (in mW) between a sample and an inert reference during an imposed thermal change, under a controlled atmosphere.

During OIT measurements, we measure the time required to induce the oxidation process under pure O2 flow at a given temperature (isotherm). The induction of the oxidation process is characterised by an increase of the heat flow, which enables to determine the OIT using different methods that will be described later.

For stabilized polymers, OIT measurements can be used to give an assessment of the level of stabilization of the material, as OIT can be seen as the time required to consume all the stabilizers.

Participants


[email protected])


UJV (Czech Republic. contact: [email protected])

Protocol for OIT measurements

The oxidation induction time (OIT) is determined on square samples of 5 ± 1 mg taken at room temperature with scissors or a razor blade from the samples delivered in a way that the sample lays as one layer on the bottom of the pan. For optimum heat flux, the highest possible contact area between sample and pan bottom should be achieved.

For OIT measurements, open (i.e. without lid) standard aluminium pans are used, and the reference pan used is an empty open standard aluminium pan, as represented in the following figure.

Figure 7.1: Photo of the inside of the DSC furnace containing the reference pan and the pan containing the sample

The conditions of OIT measurements are the following ones:

• Heating rate up to 10 °C below TOIT: 50 °C.min-1

• Heating rate up to TOIT: 5 °C.min-1

• Isothermal temperature TOIT

• Equilibration time at TOIT: 2 min

Reference (empty pan) Sample





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• Nitrogen then oxygen flows(*): 50 mL.min-1

(*) The gases pass through a mass flow controller. The flow rates are then set through the instrument control software and can be controlled during experiments.

For all OIT measurements, at least three determinations are made for each sample.

The DSC signal is registered versus the time of exposure. The OIT is then determined graphically (with the use of software). The oxidation induction time (OIT) is determined in accordance with Figure 7.2. OIT is defined as the time between t1 and t2, the former being the start of O2 flow whereas the latter is given by the intersection (onset of decomposition) of the extension of the baseline with the steepest tangent of the reaction peak. This evaluation method is called the “tangent method“.

Figure 7.2: Determination method of OIT - tangent method

“Tangent method” will be the main method of determination of OIT used. However, two other methods of evaluation of OIT exist and have also been tested through Round Robin tests.

The first alternative method used is called the “threshold method”. In this method, a parallel of Δ = 0.1 W/g higher than the baseline which intersects the measured curve in interception point X is plotted. An intersection of vertical going through X with the baseline gives the OIT (see Figure 7.3). This is the so-called threshold method and will also be evaluated.


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Figure 7.3: Determination method of OIT - threshold method

The second alternative method used corresponds to the “time to maximum rate of decomposition”. In fact, the tangent method may cause problems in the evaluation process of the OIT for some samples. Setting of a tangent and/or baseline is sometimes not easy or distinctly possible, often when commercial products like cables are measured. In such a case, it could be useful to measure the time interval to the extreme value (peak maximum) of the thermo-oxidative decomposition, i.e. the time to maximum rate of decomposition (Figure 7.4).

Figure 7.4: Determination of OIT as the time to reach the maximum rate of decomposition (time

interval in-between t1 and t2)


OIT measurements were performed by three laboratories (ENSAM. IRSN. UJV) on various materials following the above experimental protocols. The results of this Round Robin test exercise are reported in Annex 4.

As a general conclusion, the comparison of the results for all these measurements shows a very good consistency between the laboratories and thus validates the experimental protocols.


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8 EaB measurement protocol

Participants

UJV (Czech Republic, contact: [email protected]; [email protected]; [email protected]; [email protected])

VTT (Finland, contact: [email protected]; [email protected])

Standards and procedures

The procedure of tensile tests is based on or employs the appropriate requirements of the following standards:

• IEC 60811-100:2012: ”Electric and optical fibre cables – Test methods for non-metallic materials – Part 100: General IEC 60811-201:2012 „Electric and optical fibre cables – Test methods for non-metallic materials – Part 201: General tests – Measurement of insulation thickness”

• IEC 60811-201:2012/A1:2017: “Electric and optical fibre cables – Test methods for non--metallic materials – Part 201: General tests – Measurement of insulation thickness”

• IEC 60811-202:2012/A1:2017: “Electric and optical fibre cables – Test methods for non--metallic materials – Part 202: General tests – Measurement of thickness of non-metallic sheath”

• IEC 60811-203:2012: “Electric and optical fibre cables – Test methods for non-metallic materials – Part 203: General tests – Measurement of overall dimensions”

• IEC 60811-501:2012: “Electric and optical fibre cables – Test methods for non-metallic materials – Part 501: Mechanical tests – Tests for determining the mechanical properties of insulating and sheathing compounds”

• IEC 60811-606:2012: “Electric and optical fibre cables – Test methods for non-metallic materials – Part 606: Physical tests – Methods for determining the density”

• ISO 37:2017: “Rubber, vulcanized or thermoplastic – Determination of tensile stress-strain properties”

• ISO 527-1:2012: “Plastics — Determination of tensile properties — Part 1: General principles”

• ISO 527-2:2012: “Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and extrusion plastics”

• IEC/IEEE 62582-3:2012: “Nuclear power plants – Instrumentation and control important to safety – Electrical equipment condition monitoring methods – Part 3: Elongation at break”

• QA-2305/PP07: “Determination of mechanical properties of materials at static uniaxial tensile test”. Internal test procedure of Dpt 2305 ÚJV Řež.

Nevertheless, the conditions/requirements are changed/reduced/raised in some aspects, as described in paragraphs 8.4–8.7 below, coming out the UJV Rez lab own experiences.

Test materials

1) Model silane crosslinked PE, filler free (material № 1)

(RRT orient. ID: Mod1-DuB-RR-EaB-UJV/VTT)


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Dumb-bell test specimens punched in the shape according to IEC 60811-501, Figure 1,

from a sheet or tape of the thickness of 0.5 mm; colour: white, partially translucent;

surface: matt, slightly and finely wrinkled (corrugated, coarse)

2) Coaxial cable 50 ohm

Cable type: “NEXANS 279 1x0.63mm2 Cu EG SH 0.3/0.5(0.6) kV 2018 EI 3046”

(RRT orient. ID: CoXL-SCa-RR-EaB-UJV/VTT); cable outer diameter: 5.5 mm

Conductor: bare Cu (class 5), diameter of about 0.9 mm;

Insulation: filler free XLPE, colourless, matt; outer core diameter of ca 3.2 mm;

covered by PET tape and then shielded by Cu braiding;

Jacket: XLPE, black; thickness of about 0.9 mm

3) Twisted-pair cable

“NEXANS 279 1P1mm2 Cu EG CST 74 C 068 K1 SH 0.3/0.5(0.6) kV 2017”

(RRT orient. ID: OPTC-SCa-RR-EaB-UJV/VTT); cable outer diameter: 11 mm

Conductors: bare stranded (27 Cu wires of class 5 of diameter ca 0.21 mm);

Insulation: XLPE, black; outer core diameter of about 2.4 mm;

cores twisted into pair, surrounded by white shaping filler and shielded by Cu braiding;

Jacket: XLPE or EVA/EPDM (material type not specified), white; thickness of about 1.5 mm

All cross-sectional dimensions stated above have been still measured by UJV Rez as preliminary.

Sample preparation

General:

The dumbbell shaped test specimens will be preferred. Only in case that the small diameter of cable jacket or core insulation makes no possibility to prepare dumb-bell specimens, the tubular specimens will be prepared. In the case that preparation of tubular specimens will not be possible by any methods described in IEC 60811-501, par. 4.2.3c), items 1–3), or in IEC/IEEE 62582-3, Annex B3, then the core insulation or jacket material can be longitudinally cut by a sharp tool which makes possible to perform straight and smooth scission. Such specimens will be tested like being the tubular ones.

Specimens showing any visible mechanical damage are not to be used for testing. But the specimens having the surface printing only (i.e., no in-depth imprints) are acceptable.

Tubular specimens:

This type of tensile test specimens will be typically used for core insulations, and also for jackets of cables having a so small outer diameter which makes no possibility to prepare the dumb-bell test specimens. The tubular specimens of the minimal total length L of 60 mm will be prepared after transversal cutting the insulated wire samples to the pieces of the length of about 65 mm, and after uncovering the conductor at one of the ends of a prepared piece by stripping the insulation layer in the length of about 5 mm. Then, the metallic conductor and possible rests of inner separators (e.g., mica layer) and all outer layers covering the core insulation (shielding, rests of fillers etc.) will be carefully removed from the tubular test piece. This removing will be done only mechanically, without damaging the insulation material.

A note: Considering the gripping length of 30 mm, and the height of jaw end-tabs of 12.7 mm (1/2 inch), then the minimum total specimen length L of about 60 mm is necessary to be applied to ensure the protrusion of both tubular specimens ends of about 2 mm (30 + 2∙12.7 + 2∙2 ≐ 59.4). For another height of end-tabs used, the specimen length L should be adequately changed.


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The cross-section area A of each tubular specimen will be individually determined for all prepared pieces and its value will be stated in the respective tensile test record. It will be determined by either of the following methods (the method described in item (a) is preferred):

a) By calculation from the outer diameter D of each tubular specimen (measured by a proper mechanical or optical device having the duly calibration) and its inner diameter d, determined as a collective characteristic either from the nominal (or actually measured) diameter of the conductor (when it has circular cross-section and no separating layers are used on it), or otherwise by an optical device. Then,

A = π⋅(D 2 – d 2)/4.

A note: Resulting outer diameter D of a tubular specimen will be determined as the minimal measured value obtained from the following 3 sites along its working length: in the middle of a specimen and in the sites of about 10–15 mm distance from the specimen middle. Together with this, three measurements will be performed for each of these three measured sites, each measurement will be performed in the direction turned through the angle of about 60 °.

A note: According to IEC /IEEE 62582-3, par. 5.5.2, the best estimate shall be made of the cross-sectional area for tubular specimens, where the insulation overlays a stranded conductor; but there is no procedure prescribed or proposed for that best estimate. A possible procedure for getting the best estimate dbest of inner diameter d of a tubular insulation overlaying a stranded conductor is shown in Figure 8.1. Here, the assumption is made that the “apparent” outer diameter d = dbest of a conductor is equal to the inner diameter d of a tubular specimen. Then, the dbest can be estimated as the arithmetical middle of the mean values of two measured diameter modes, d1 and d2 , if a calliper or a vernier (and/or a dial) thickness gauge having flat contact surfaces is used for measurement of cross-sectional dimensions of a stranded conductor.

d = dbest = ½ ∙ (d1 + d2)

Figure 8.1: The way of measurement of apparent mean diameter of a stranded conductor (having 27 strands) which is then used for determination of inner diameter of surrounding

core insulation

b) By calculation from the length L and the mass m which will be individually determined for each of the tubular specimens, and from the mass density ϱ of unpolluted insulation material determined as a collective characteristic for a representative sampling made for an unaged insulation sample and then valid for all specimens in all measured batches (either unaged or aged). Then,

A = m/(ϱ⋅L ).

d

d


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A note: The application of all methods described in IEC 60811-606 for determination of the mass density ϱ is possible, except of the pycnometer one in cases stated in the next note.

A note: The use of volumetric (pycnometer) method for cross-section area determination — based on the volume and specimen length measurement, described, e.g., in the clause 4.2.4, par. b3) of IEC 60811-501 — is not suitable for specimens having traces (striations) of the stranded conductor (due to the risk of air bubbles which may remain inside striations or other possibly unevennesses of inner surface), even in the case of tubular specimens are also longitudinally cut.

Dumb-bell specimens:

Dumb-bell tensile test specimens will be used for cable sheaths. Only the outer sheath (i.e. jacket) will be tested. The dumb-bell specimen puncher shaped according to Figure 1 in IEC 60811-501:2012 will be applied (this shape is identical with the test specimen of type 5A in IEC 527-2:2012, and also with the test specimen of type 2 in ISO 37).

Test specimen preparation and their cross-section A determination will be in accordance with IEC 60811-501, paragraphs 4.3.2 to 4.3.4, with following exclusions/exceptions/deviations or more detailed specifications:

a) Any of both jacket surfaces will not be machined or grinded-off, so the test dumb-bell shaped specimens will be punched from the jacket in its state “as it is”, i.e., small surface unevenness will be accepted, and no rest layers attached or even glued to the jacket are supposed and expected. But the punched specimens having imprinted cable marking or visible outer surface scratches or other defects will be eliminated before tests.

b) Due to the central cutting (punching) of dumb-bell test specimens, the procedure of determination of jacket thickness t according to IEC 60811-202 is not applicable, and the dumb-bell thickness will be measured until on prepared specimens.

Rather the dumb-bell width determined individually for each test specimen according to the procedure described in the IEC 60811-501, par. 4.2.4, item a), is preferred than the collective one (i.e., for the all batch) described ibid.

The thickness of a dumb-bell specimen having the traces (striations) from braiding or twisted conductors or cores shall to be measured in the thinnest location, i.e., in the bottom stroke of a striae using the device having the measuring surfaces properly rounded.

c) The method of collective dumb-bell thickness t or collective cross-section area A determination by using the density method similarly to IEC 60811-501, par. 4.3.4, item 2, is not advised until the ground plan area of the die actually used for punching the dumb-bell specimens will be planimetrically determined, as it can sometimes differ from the ground plan area of the die in the Fig. 1 from the IEC 60811-501. This difference can be caused by dimensional tolerances, particularly in the length of the end parts of a dumb-bell die which may too vary, as the total specimen length has not determined its positive tolerance — see into the Std. ISO 527-2.

Sample conditioning

Prepared test specimens should be conditioned at room temperature (23 ± 3) °C for at least 24 hours prior to testing. The relative humidity should not exceed the interval of 30–75 %.


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Test parameters

All specimens will be tested on a tensile testing machine using such a load cell which has the load measurement accuracy better (i.e. less) than ±1 % of maximal measured force during a test. The accuracy for specimen absolute elongation reading is not to be exceeding ±1 %.

For both tubular and dumb-bell test specimens, the primary detection of absolute specimen deformation [mm] will be performed by cross-head motion (jaw separation) — a characteristic obtained in such a way is called nominal elongation (εt), see the ISO 527-1.

For information purposes only, also the parallel detection of absolute specimen deformation via a contact or an optical extensometer can be applied —deformation obtained in such a way is here further called elongation (ε) (or standard elongation).

The following test parameters will be applied:

a) Testing (cross-head) speed: 50 mm/min b) Initial grip distance for tubular specimens: 30 mm c) Initial grip distance for dumb-bell specimens: 50 mm d) Rate of tensile test data acquisition: at least 20 pts/s

The tolerances for above items a)–c) are given in IEC/IEEE 62582-3.

For each batch — either of tubular or dumb-bell test specimens — at least 9 test pieces will be tested and evaluated, with the objective of better checking the reproducibility of results.

Notes:

The nominal relative elongation at break (εtB) will be determined using the gauge length L0 equal to initial grip distance of 50 mm for dumb-bell test specimen, respective of 30 mm for tubular test specimens. For the purpose of the “standard” elongation at break (εB) evaluation, the extensometer gauge length L0 will be set to 20 mm for both types of specimens. For more details on above definitions, see into ISO 527-1. If no proper extensometer type will be available for any of specimen types, only the relative nominal elongation at break (εtB) will be reported.

The use of additional soft inserts into the end-tabs portion of the tubular specimens is not recommended within this round robin project, as it includes other uncertainties among laboratories (the gripping force is not prescribed in any of the cited standards). Therefore, if some specimens from a batch will break in grips still during their clamping into grips, the (standard, resp. nominal) elongation at break (εB, resp. εtB) will be regarded equal to zero, as well as the tensile strength σmax, and these results will be incorporated into the statistics. Only the results stemming from the sample behaviour showing the breaking inside grips will be discarded as unsatisfactory.

Test environment

• Testing medium: Air.

• Testing temperature: Controlled in the range 23 ±3 °C for all batches.

• Relative humidity (R.H.): Natural (i.e., without regulation) is admissible, if it varies in the range 30–75 % among batches and is within interval ± 10 %during testing an individual batch.

• Temperature-humidity recording: Data logging of these environment parameters is recommended with data acquisition interval not higher than 2 hours, or manual writing of these data always before testing a batch can be used.

• Specimens conditioning: In the test room, at least 24 hours before testing.


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Results

The results of tensile tests will be reported only via tables, providing that all data concerning the tests and required by the standard IEC/IEEE 62582-3:2012 are available for all batches.

Following data shall be available in test reports:

• Laboratory ID, including the ID of a person which prepared the samples and ID of a person performed the tensile testing (if possible, it should be the same persons during all the Round Robin Test)

• Material ID and its history (e.g., time and location of a NPP installation or conditions of artificial ageing, if it was performed)

• Position of sampling (cutting) the specimens (material) from a cable sample

• Specimens conditioning before testing and ambient environment parameters during testing

• Place and date of the measurements

• Number of specimens measured

• Details of specimen preparation (deviations or difficulties during this)

• Specimen type — dumb-bell/tubular

• Dimensions of specimen and info whether they are individual or collective ones

• Tensile instrument used and software version used for analysis/evaluation of results

• Extensometer type used (if used)

• Type of grips used to clamp specimens

• Test speed used (velocity of cross-head separation)

• Individual elongation at break values (standard or nominal, εB or εtB in %), and tensile strength values, σmax . Please carefully indicate which elongation at break was calculated from extensometer gauge length (“standard” elongation at break) and which from grip separation (nominal elongation at break).

• Following statistics shall be reported for each of batches: arithmetical means; medians; standard deviations

• Any values excluded from calculation of the statistics shall be indicated in a comments column (e.g., because of failure in the grips or slippage)

• Examples of typical plots “load versus elongation”, or “stress versus relative elongation”. Any atypical plots shall also be included.

References to calibration certificates of used equipment (gauges, other measuring devices), date and validity or frequency interval of the calibrations need not be reported, but they will be available in the testing lab.

Acceptance criteria

Only nominal elongation at break will be obligatory compared, the comparison for all other possible characteristics obtained from tensile test is only informative. Acceptance criterion for satisfactory fit of two labs (ÚJV Řež versus VTT) is specified as follows:

At least one of below conditions must be fulfilled:


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a) The ratio of ΔεtB / ε̅tB ≤ 0.1 (i.e. 10 %), where ΔεtB = |εtB1 – εtB2| is the “difference of individual medians of UJV (index 1) and VTT (index 2) laboratories”, and ε̅tB = (εtB1 + εtB2)/2 is their mean value.

b) The intersection of both 95.4-% confidence intervals around the individual medians should not be empty set; i.e., {⟨ εtB1 – 2⋅δεtB1 ; εtB1 + 2⋅δεtB1 ⟩} ⋂ {⟨ εtB2 – 2⋅δεtB2 ; εtB2 + 2⋅δεtB2 ⟩} ≠ { }, where δεtB1 (resp. δεtB2) is one standard deviation of εtB1 (resp. of εtB2), considering the normal (Gauss) distribution.


These experimental measurements were tested through the round robin test exercise between VTT/Finland and UJV/Czech Republic. The results of this round robin test exercise are reported in Annex 5.

The comparison of results for all these measurements shows that the acceptance criterion is fulfilled and thus the experimental protocol can be considered as validated.


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9 EPR measurement protocol

Introduction

EPR has matured into a powerful, versatile, non-destructive, and nonintrusive analytical method. Unlike many other techniques, EPR yields meaningful structural and dynamical information, even from ongoing chemical or physical processes without influencing the process itself. Therefore, it is an ideal complementary technique for other methods in a wide range of studies and application areas, like chemistry, physics, material research, ionizing radiation, biology and medicine.

The energy differences we study in EPR spectroscopy are predominately due to the interaction of unpaired electrons in the sample with a magnetic field produced by a magnet in the laboratory. This effect is called the Zeeman effect. Because the electron has a magnetic moment, it acts like a compass or a bar magnet when you place it in a magnetic field, B0. It will have a state of lowest energy when the moment of the electron, μ, is aligned with the magnetic field and a state of highest energy when μ is aligned against the magnetic field. (See Figure 2-3.) The two states are labelled by the projection of the electron spin, Ms, on the direction of the magnetic field.

From quantum mechanics, we obtain the most basic equations of EPR:

E = g B B0 Ms = ± g B B0

and

E = h = g BB0.

g is the g-factor, μB is the Bohr magneton, B0 is magnetic field.

Figure 9.1. Variation of the spin state energies as a function of the applied magnetic field.

Measurement of g-factors can give us some useful information; however, it does not tell us much about the molecular structure of our sample. Fortunately, the unpaired electron, which gives us the EPR spectrum, is very sensitive to its local surroundings. The nuclei of the atoms in a molecule or complex often have a magnetic moment, which produces a local magnetic field at the electron. The interaction between the electron and the nuclei is called the hyperfine interaction. It gives us a wealth of information about our sample such as the identity and number of atoms which make up a radical or complex as well as their distances from the unpaired electron. The magnetic moment of the nucleus acts like a bar magnet (albeit a weaker magnet than the electron) and produces a magnetic field at the electron, BI. This magnetic field opposes or adds to the magnetic field from the laboratory magnet, depending on the alignment of the moment of the nucleus. When BI adds to the magnetic field, we


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need less magnetic field from our laboratory magnet and therefore the field for resonance is lowered by BI. The opposite is true when BI opposes the laboratory field. For a spin 1/2 nucleus such as a hydrogen nucleus (proton), we observe that our single EPR absorption signal splits into two signals which are each BI away from the original signal.

Figure 9.2. Splitting in an EPR signal due to the local magnetic field of a nearby nucleus.

For nuclei with spins other than 1/2, the number of lines equals:

Number of Lines = 2I + 1

where I is the spin quantum number of the nucleus.

Participants

INCT, Poland. Contacts: [email protected], [email protected], [email protected]).

Preparation of samples

The selection of samples and their irradiation in gamma cells result from the schedule of TeaM Cables Project (TC). The physical shape of samples has to ensure homogeneity of the absorbed microwaves, but their geometry is not limited (powder, scraps, slices, roller, cylinder etc.). Before measurement the appropriate identity of each sample shall be introduced. Identification used should be complementary to the TC database code.

Irradiation in gamma chambers shall generate unpaired spins, the population of which cannot be less than 1012. The irradiation temperature, absorbed dose and dose rate affect the EPR signals and must therefore be controlled, saved and archived. Samples after irradiation with gamma rays and between successive measurements are stored in the dark at ambient temperature or in thermobox. They are kept in an air atmosphere. The humidity during post-irradiation storage can affect the EPR signal. Very humid environments may cause water condensation in the cavity when the sample is cooled with a variable temperature system, which prevents measurement. Before measurements, sufficient time should be allowed for samples to achieve a state of equilibrium with ambient conditions.

EPR experiments

An X-band EPR spectrometer equipped with a cryostat and a high-temperature resonant cavity is used to record EPR spectra in various conditions. Depending on the requirements, the EPR cavity can be cooled using a cryostat that changes the temperature in the range of 100-300 K or heated to elevated temperatures.

The magnetic field controller and frequency meter are required to precisely determine g-factor. EPR measurements are conducted at 21oC in an air-conditioning laboratory, unless otherwise indicated.


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Time since irradiation significantly affects the EPR signal, therefore the measurement is carried out directly upon irradiation. The kinetics of radical decay is established by measuring EPR signals after the expiration of a predetermined time at selected temperatures. The EPR spectrometer registers the first derivative of the absorption curve. Verification of the spectrometer is performed by measuring the EPR reference material – DPPH standard which shows the signal at g = 2.0036 (calibration).

The irradiated samples are inserted into high-quality quartz tubes that does not interfere with the EPR signal. The EPR tube filled with the sample is placed in the holder accurately in central position in the EPR cavity, i.e. in the electric field minimum and the magnetic field maximum to obtain the biggest signals and the highest sensitivity, using ruler for precision positioning of sample in the cylindrical cavity.

EPR parameters:

The Quality factor Q of resonator shall be not lower than 6000.

The following settings are recommended: magnetic field with a field scan range of 20 mT about the centre field; modulation frequency 100 kHz; magnetic field modulation amplitude in the range from 0.05 to 0.2 mT; number of points 1000; receiver gain 30 db; sweep time 30-40 s. The influence of microwave power in the range of 0.100-100 mW on the intensity and shape of the spectrum shall be examined. The number of scans is each time adapted to the intensity of the signal in order to achieved sufficient signal-to-noise ratio.

To normalise the intensity of the EPR signal, the mass of the sample should be controlled within ± 0.1 mg.

If the sample is measured at specified intervals, the position of the EPR tube in cavity shall be precisely in the same place as in previous measurements.

Documentation and data analysis

The dataset and spectra are stored and saved in a format compatible with Excel. The documentation contains sample codes and measurement parameters necessary for further interpretation of the EPR spectra.

The software WinEPR and Simfonia are used to analyse and simulate the EPR spectra.


These experimental measurements were tested through the round robin test exercise between INCT/Poland, IRSN/France and UJV/Czech Republic. The results of this round robin test exercise are reported in Annex 1.


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10 Swelling test measurement protocol

Introduction

When a crosslinked polymer is placed in a good solvent, rather than dissolving completely in the solvent, it will absorb the solvent and swell to a degree depending on the solvent and the structure of the polymer. This phenomenon of limited swelling is characteristic of polymers with network structures (i.e. crosslinked polymers). This extent of swelling represents a competition between two opposing forces. The free energy of mixing causes the absorption of solvent in the polymer, which induces the expansion of the polymer network. On the other hand, as more solvent is absorbed, the polymer chains in the crosslinked polymer network begin to elongate, which generates an elastic retractive force in opposition to this deformation. Equilibrium is attained when those two forces balance each other.

Figure 10.1: Illustration of the swelling of a crosslinked polymer network when placed in a good solvent

Swelling measurements provide information on the polymer network, as the extent of swelling is related to the affinity between the solvent and the polymer, but also to the concentration and the molecular weight of elastically active chains (i.e. chains participating to the network). This method was formulized by Flory and Rehner in 1940s (Flory and Rehner, 1943). The Flory-Rehner equation is given as:

C = −1

Vs ln(1 − Vr0) + μ Vr0

2 + Vr0

Vr0

13 −

Vr02

Where C represents the concentration of effective chains (mol.cm-3), Vr0 the volume fraction of the polymer in swollen gel, μ the Flory-Huggins solvent/polymer interaction parameters and Vs the molar volume of the solvent.

The volume fraction of the polymer, Vr0, can be expressed as follows:

Vr0 = 1

1 +(f − 1) ρpol

ρsol

= 1

1 +(

mswmgel

− 1) ρpol

ρsol

Where f represents the solvent uptake factor, msw the weight of the swollen gel, mgel the weight of the dried gel, ρpol the density of the polymer and ρsol the density of the solvent.

If considering a homogeneous network, the average molecular weight between crosslinks, Mc (g.mol-1), can be calculated using the following equation:


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Mc = ρpol

C

Previous studies (Celina and George, 1995; Hendra et al., 1987) have used the Flory – Rehner equation to calculate the average molecular weight of elastically active chains in case of a crosslinked PE swollen in refluxing p-xylene, and used the following values in their calculations: μ = 0.31, Vs = 139.3 cm3.mol-1, ρsol = 0.806 g.cm-3 (at 139°C) and ρpol = 0.761 g.cm-3 (at 139 °C).

In case of unfilled crosslinked polymers, the swelling restriction is only due to the polymer crosslinks, thus, by applying the Flory-Rehner theory, the degree of crosslink density can be estimated. However, in case of filled crosslinked polymers, the introduction of rigid filler particles can lead to serious theoretical and practical complications. The most basic one being the inability of the network to undergo deformations in proportion with the sample dimensions.

In their study, Lorentz and Parks (Lorenz and Parks, 1961) have proposed that swelling of the bulk crosslinked polymer would be essentially the same for the filled and unfilled polymer, at the exception of the interfacial region where the restriction to swelling would be maximum due to the adsorption of polymer chains on filler. In another study, Kraus (Kraus, 1963) proposed an empirical approach for filled polymers which takes into account the presence of filler particles and their interaction with the polymer matrix. Kraus distinguished two cases. In case no filler-matrix interactions exist at swollen state (i.e. when filler/polymer matrix interactions are purely physical at solid state), filler particles do not restrict the swelling of the polymer network, which undergo an isotropic dilatation similar to the one of the unfilled polymer. As the solvent molecules penetrate through the polymer network and reach the filler/polymer interphase, they remove the physical interactions between the fillers and the polymer by dissolving the polymer chains in contact with the filler surface. Cavities, filled with solvent, thus develop around each filler particle as the polymer swells. Formation of these cavities filled with solvent basically induces an increase in the apparent swelling of the polymer network, as observed by Berriot et al. (Berriot et al., 2002).

In case of adhering solid fillers (i.e. when filler/polymer interactions are permanent), as the bonds between filler particles and polymer chains remain intact at swollen state (they cannot be undone by solvent penetration), there is a restriction of the swelling, in particular at the vicinity of the particles’ surface. In this case, the polymer cannot sustain an isotropic expansion, as it remains connected to the particles. The swelling of the polymer network is thus restricted, especially in the vicinity of the filler particles, and no cavities are formed around the filler particles. In this approach, the swelling ratio is supposed to variate linearly with φ/(1-φ), where φ is the volume fraction of filler. Kraus’ correction of Flory-Rehner equation to calculate the concentration of elastically active chains, taking the presence of filler particles into account is as follows:

C =Vr0

Vs ln(1 − Vr) + μ Vr

2 + Vr

Vr2 − Vr

13 Vr0

23

Where Vr is the apparent volume fraction of the polymer in the swollen gel, and Vr0 the “true” volume fraction of polymer in the swollen gel (i.e. without filler).

Participants


[email protected])





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Swelling test protocol

The solvent swelling measurements were performed under refluxing p-xylene (boiling point ≈ 139 °C), as mentioned in ATSM 2765-01.

A sample amount in the range of 30 ± 5 mg of XLPE (mi) was accurately weighted to ± 0.01 mg and placed in a round-bottomed flask containing p-xylene. Reflux conditions were enabled by the means of a reflux setup consisting on a round-bottomed flask connected to a water-cooled condenser and an adjustable heating mantle, as represented in the following figure.

Figure 10.2: Reflux setup used to perform swelling measurements of XLPE in p-xylene

The sample was extracted in refluxing p-xylene for 24 h, after which it was recovered from the solvent with the help of a funnel and filter paper. Excess solvent on the sample’s surface was carefully removed with the help of filter paper, after which the sample was rapidly transferred into a sealable pre-weighted sample vial and weighted to determine the weight of swollen gel (msw). Final drying was then carried out in a vacuum chamber at 80 °C to obtain the weight of the dried gel (mgel).

By the mean of this experiment, gel content (insoluble fraction, i.e. the proportion of chains participating in the network), solvent extraction ratio (soluble fraction, i.e. the proportion of chains which do not belong to the network), swelling ratio and solvent uptake factor can be calculated from the following relations:

Extraction ratio (%) = Fs =mi − mgel

mi× 100

Gel content (%) = G =mgel

mi× 100 = 100 − Fs

Swelling ratio (%) = Q =msw − mgel

mgel× 100

Solvent uptake factor = f = msw

mgel

Where mi, msw and mgel represent, respectively, the initial weight of the sample, the weight of the swollen gel and the weight of the dried gel.

In case of filled samples, the procedure performed was the same as for unfilled samples. However, the swelling ratio of the polymer and the extraction ratio are calculated taking into account the non-swelling of the fillers and the fact that the fillers are not extracted during the swelling test (TGA analysis

Water in

Water out

Round-bottom flask containing the sample

in p-xylene

Heating mantle

Condenser


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was performed for filled samples after swelling test to confirm the non-extraction of fillers during the test):

Extraction ratio (%) = Fs =mi − mgel

mi (1 − ε)× 100

Gel content (%) = G = 100 − Fs

Swelling ratio (%) = Q =msw − mgel

mgel (1 − ε)× 100

Where ε represents the fraction of filler in the polymer.

Results obtained for unaged Model 1

As mentioned before, extraction and swelling of crosslinked polyethylene in refluxing p-xylene (~ 139 °C) is commonly performed in order to determine the gel content and crosslink density of the polymer network.

The following figure represents photos of material model 1 after extraction and swelling in refluxing p-xylene for 48 h (swollen gel) and this same material after drying under vacuum for 24 h (dried gel).

Figure10.3: Photos of Model 1 in swollen state (left) and in dried state (right) after extraction and swelling in refluxing p-xylene

Different extraction and swelling time in refluxing p-xylene were performed on model 1 (neat silane-XLPE) in order to determine a procedure enabling both to extract all soluble fraction of the material and to reach the equilibrium of swelling of the polymer network. The results obtained are represented on Figure 10.4 and recapitulated in Table 10.1.

From these results obtained on model 1, it can be observed that the soluble fraction can be completely extracted from the sample after 18 h in refluxing p-xylene. Extraction experiments of Mod1 in p-xylene give an extraction ratio of 29 ± 1%, i.e. a gel content of 71 ± 1%.

Concerning the swelling of the material, the error in the evaluation of the swelling ratio, and hence in the average molecular weight between crosslinks, is higher. This error has been found to be about 10% and may come from the determination of the weight of the gel in its swollen state during the experiments. In their study on crosslinked polyethylene, Hendra et al. (Hendra et al., 1987) considered that errors in the evaluation of the average separation of crosslinks are about 10-15%, which is the same order of magnitude than what has been found here.


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Table 10.1: Results of extraction and swelling experiments performed on Model 1 (neat XLPE) for different immersion time in refluxing p-xylene

Immersion time in refluxing p-xylene (h)

Extraction ratio (%)

Gel content (%) Swelling ratio

(%) Solvent uptake

factor

0 0 / 0 0

5 26.7 73.3 279 3.8

8 26.8 73.2 386 4.9

18 28.9 ± 0.3 71.1 ± 0.3 / /

24 28.7 ± 0.8 71.3 ± 0.8 475 ± 44 5.8 ± 0.4

30 29.4 ± 0.2 70.6 ± 0.2 / /

48 29.1 ± 0.1 70.9 ± 0.1 432 ± 47 5.3 ± 0.5

Figure 10.4: a) Extraction ratio and b) swelling ratio against immersing time in refluxing p-xylene obtained for model 1 (neat XLPE)

Regarding this error bar, it can be considered that 24 h of swelling in p-xylene is sufficient to achieve the swelling equilibrium, giving a swelling ratio of 475 ± 44%.

As mentioned before, swelling experiment can be used to evaluate the average separation of crosslinks using the Flory-Rehner equation. For model 1, the results obtain are summarized in the following table (Table 10.2).

a) b)


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Table 10.2: Results of swelling experiments for Mod1 after extraction and swelling in refluxing p-xylene for 24h

Swelling test of Mod1-Tpe-UnA [24 h; 139 °C]

Gel content (%) 71 ± 1

Swelling ratio (%) 475 ± 44

Solvent uptake ratio, f 5.8 ± 0.4

Volume fraction of polymer in gel, Vr0 0.17 ± 0.01

Concentration of effective chains, C (mol.cm-3) (1.1 ± 0.2) 10-4

Average molecular weight between crosslinks, Mc (g.mol-1) 7546 ± 1193

References

ASTM 2765-01. Standard Test Methods for determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics

Berriot, J., Lequeux, F., Montes, H., and Pernot, H. (2002). Reinforcement of model filled elastomers: experimental and theoretical approach of swelling properties. Polymer 43, 6131–6138.

Celina, M., and George, G.A. (1995). Characterisation and degradation studies of peroxide and silane crosslinked polyethylene. Polym. Degrad. Stab. 48, 297–312.

Flory, P.J., and Rehner, J. (1943). Statistical Mechanics of Cross‐Linked Polymer Networks II. Swelling. J. Chem. Phys. 11, 521–526.

Hendra, P.J., Peacock, A.J., and Willis, H.A. (1987). The morphology of linear polyethylenes crosslinked in their melts. The structure of melt crystallized polymers in general. Polymer 28, 705–709.

Kraus, G. (1963). Swelling of filler‐reinforced vulcanizates. J. Appl. Polym. Sci. 7, 861–871.

Lorenz, O., and Parks, C.R. (1961). The crosslinking efficiency of some vulcanizing agents in natural rubber. J. Polym. Sci. 50, 299–312.

Planes, E., Chazeau, L., Vigier, G., Fournier, J., and Stevenson-Royaud, I. (2010). Influence of fillers on mechanical properties of ATH filled EPDM during ageing by gamma irradiation. Polym. Degrad. Stab. 95, 1029–1038.


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11 Gas analysis protocol

Introduction

Instantaneous gas emission rates, at the different ages, are determined using a two-step procedure. On the first step, polymers are irradiated at various doses, by UJV Rez in the Panoza irradiator, with the other samples of the TeaM Cables European project. During the second step, polymers are irradiated at low doses in a closed container and the emitted gases are analysed. Between the two irradiation steps, samples are stored under inert atmosphere and in dark to prevent or at least reduce further ageing by oxygen and UV rays.

Using this two-step procedure presents great advantages. At a given dose, a single step irradiation in a closed container would have given the cumulated emission rate instead of the instantaneous emission rate. Moreover, irradiating in one single step should have led to the possible complete consumption of the oxygen present in the glass container, leading to the variation of the atmosphere composition through the irradiation. Finally, this excludes H2 back reactions, because high pressures of H2 in the container can potentially lead to a bias in gas quantification.

Participants

CEA, France. Contact: [email protected], [email protected].

Gas analysis protocol

11.3.1 Second-step irradiation conditions

Polymer samples are placed in glass containers equipped with a valve, under between 700 and 800 mbar of reconstituted air (20.0 % O2, 77.99 % N2, 2.01 % Kr). Krypton is used as a tracer and enables to determine the final pressure. Sample masses are estimated to obtain, at the end of the irradiation, a final content in H2 of about 1%vol and an oxygen consumption of about half the initial concentration.

To optimize the masses of polymers in the glass ampoules, preliminary experiments were performed at PCR (CEA, Saclay, France), using a 137Cs source. The characteristics of this irradiator (Nordion Gammacell®) are a dose equal to 24 kGy and dose rate equal to 0.3 kGy.h-1.

Final gamma irradiations took place at LABRA (CEA Saclay, France), using a 60Co source. Doses are equal to 12 kGy and 24 kGy and dose rate used is about 1.0 kGy.h-1.

No electronic correction is made to take into account the electronic density difference between water and polymers. Uncertainties on given doses are less than 6%. For each material, two low and different doses were chosen to check the linearity of the formation/consumption of the studied gases.

11.3.2 Gas analysis

Gas analyses are performed with a high resolution quantitative gas mass spectrometer with direct inlet for chemical and isotopic analysis (Thermo Fischer Scientific MAT-271). Ionization occurs by electron impact, mass separation is performed with a magnetic sector, and ion detection by Faraday cup and electron multiplier. The mass ranges from 1 to 200 amu and the detection limit is about 1 ppm depending on the gas matrix and mass interference (Aregbe, 1996; Park, 2004). The gas mixture is admitted to the mass spectrometer via a “molecular” leak which means that the gas flow at the leak is in the molecular flow regime. Gas composition can be determined accurately because there is no mass discrimination and the leak rate of each gas is known using Graham’s law (inversely proportional to the square root of the gas molar mass).


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We define the instantaneous gas emission rate 1

𝑑∙

𝑑[𝑋]

𝑑𝑡, called also the radiation chemical yield at dose

D, 𝐺𝐷, in mol.J-1, using the following equation:

𝐺𝐷 =1

𝑑∙

𝑑[𝑋]

𝑑𝑡=

𝑃𝑓 ∙ %𝑣𝑜𝑙 ∙ 𝑉𝑓𝑟𝑒𝑒

𝑅 ∙ 𝑇 ∙ ∆𝐷 ∙ 𝑚

d is the dose rate in Gy.s-1, [𝑋] the X concentration in mol.kg-1 measured after irradiation at a given dose D, 𝑃𝑓 the total pressure in the glass ampoule at the end of the irradiation in Pa, %𝑣𝑜𝑙 the gas

volume fraction determined by gas mass spectrometry, 𝑉𝑓𝑟𝑒𝑒 the free volume in the glass ampoule in

m3, 𝑅 the gas constant, 𝑇 the sample’s temperature under irradiation in K, and m the mass of the irradiated sample in kg. 𝐷 is the dose in kGy reached during the first irradiation step (also called pre-aging step) at UJV Rez, whereas ∆𝐷 is the deposited dose during the second step in Gy.

References

Aregbe Y., Valkiers S., Mayer K., De Bièvre P. (1996). Comparative isotopic measurements on xenon and krypton. Int. J. Mass Spectrom. Ion Processes 153. L1

Park S.Y., Kim J.S., Lee J.B., Esler M.B., Davis R.S., Wielgosz R.I. (2004). A redetermination of the argon content of air for buoyancy corrections in mass standard comparisons. Metrologia 41. 387


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12 UV measurement protocol

Introduction

UV (Ultraviolet) spectroscopy is a non-destructive technique based on the interaction of ultraviolet light with matter. The principle of UV spectroscopy is the same as FTIR spectroscopy, at the difference that, as can be seen in the following Figure representing the electromagnetic spectrum, UV spectroscopy involves photons of higher energy compared to IR spectroscopy. Thus, in UV-Visible spectral range, which basically comprises between 200 nm and 700 nm, absorption of photons can cause transitions between the different electronic energy levels (i.e. transition of an electron from a lower energy state to a higher one). The absorption wavelengths depend in this case on the nature of the molecular orbitals involved.

Figure 12.1 : Electromagnetic spectrum

UV-Visible spectra generally show only a few broad absorbance bands as most of absorption in this spectral range results from the presence of π-bonds (i.e. unsaturated bonds). In fact, most of the absorption in UV-Visible spectral range can be attributed to a group of molecules called “chromophores” (e.g. C=C, C=O, C=N, etc.).

As these chemical functional groups have specific absorbance wavelength range, the presence of an absorbance band at a particular wavelength can be a good indicator of the presence of a chromophore. However, as for FTIR spectroscopy, the position of the maximum of absorbance is not fixed and depends on the molecular environment of the molecule. For instance, when the molecule presents a conjugated structure (i.e. few double bonds in chain), both the intensity and the wavelength of the absorption band increase (respectively a “hyperchromic” and “bathochromic” effect).

As for FTIR spectroscopy, UV spectroscopy can be used to quantify chromophore molecules using Beer-Lambert law.

Participants


[email protected])

Protocol for UV measurements

UV spectroscopy is performed using a Perkin Elmer lambda 35 UV spectrometer. UV spectra are recorded in transmission mode and will hence only be performed on films. For each sample, three UV spectra will be recorded on three different days. The spectra will be recorded on absorbance mode,



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and the spectral range scanned will be from 200 nm to 400 nm. The slit width is of 2 nm and the scan speed of 60 nm/min.

Results obtained for unaged samples

In this study, UV spectroscopy can be useful in order to follow the disappearance of the phenolic antioxidant, as it has an aromatic ring and is, hence, supposed to absorb in the UV spectral range. Möller et al., for instance, identified two distinct bands, at 274 nm and 282 nm, for a film of Irganox 1076 of 200 µm thick (Möller and Gevert, 1996).

The spectra obtained for unfilled unstabilized (Mod1) and stabilized samples (Mod2, Mod3, and Mod4) are presented in the following Figure and were obtained from tapes (0.5 mm thick).

Figure 12.2: UV spectra obtained for unaged unfilled samples (tapes of 0.5 mm thickness)

As shown on the spectra, a large band can be observed for Mod2 and Mod4 between 250 nm and 300 nm, which is associated to the phenol band. In case of Mod4, two distinct peaks can be identified, at 275 nm and 283 nm, as observed by Möller and coworkers. However, in case of Mod2, the band seems to saturate.

The thickness of the tapes (500 µm thick) might be an issue for UV spectroscopy, as some bands seem to saturate. Thinner samples could be used to quantify phenol function, and thus phenolic antioxidant, initially and during ageing. However, in case of XLPE tapes, thinner films could not be obtained, due to the difficulty to microtome the tapes.

References

Gauglitz, G., and Vo-Dinh, T. (2006). Handbook of Spectroscopy (John Wiley & Sons).

Möller, K., and Gevert, T. (1996). A solid-state investigation of the desorption/evaporation of hindered phenols from low density polyethylene using FTIR and UV spectroscopy with integrating sphere: The effect of molecular size on the desorption. Journal of Applied Polymer Science 61, 1149–1162.

Owen, T. (1996). Fundamentals of UV-visible Spectroscopy: A Primer (Hewlett Packard).


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13 Indentation measurement protocol

Introduction

The principle of micro-indentation measures is to push a point subjected to a load into the material. During the test, the force applied, as well as the movement of the tip as a function of time, are recorded, both in charge and in discharge. This allows the force-displacement curves to be obtained, representing the force applied according to the depth of penetration of the tip in the material (Figure 13.1). The nature of the discharge curve depends on the elastic properties of the material. It allows deducing the elastic modulus.

The indentation operating software allows direct access to the material reduced modulus (ER) and its Vickers hardness (HV), calculated with the Oliver and Pharr method (Iqbal et al., 2011).

The reduced modulus is obtained from the initial slope of the discharge curve (S) according to the following relationship:

𝑬𝒓 =√𝝅𝑺

𝟐𝜷√𝑨𝒄

S is the initial slope of the discharge curve, β is a form factor dependent on the type of indenter (β = 1.012 in the case of a Vickers indentor) and Ac is the proposed contact area. This depends on the actual contact depth of the indenter with the sample (HC) and the geometry of the indenter. For a Vickers indenter, Ac is defined by the following equation:

𝑨𝒄 = 𝟒 𝒕𝒂𝒏𝟐𝜶 × 𝒉𝒄𝟐

α is the opening angle of the Indenter (68°), and hc is the actual depth of contact.

𝒉𝒄 = 𝒉𝒎𝒂𝒙 − 𝜺(𝒉𝒎𝒂𝒙 − 𝒉𝒓)

hmax the maximum indentation depth and hr depth at the discharge (Figure 1). ε depends on the geometry of the indenter: 0.73 for a conical shape.

Figure 13.1: Schematic graph presenting the multiple phases of the loading-unloading cycle during indentation tests


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The Young module of the sample is determined from the reduced module according to the following equation:

𝑬 =𝟏

𝟏 − 𝛝𝟐

𝑬𝒓−

𝟏 − 𝝑𝒊𝟐

𝑬𝒊

ϑ is the Poisson coefficient of the sample (ϑXLPE Silane = 0,42). ϑi and Ei are respectively Poisson coefficient and Young modulus of the diamond indenter, equal to 0.07 and 1147 GPa.

The Vickers hardness (HV) is calculated from the following relationship:

𝑯𝑽 =𝟐𝑭𝒎𝒂𝒙

𝐃²∗ 𝐬𝐢𝐧 𝜶

α is the opening angle of the Indenter (68°), Fmax is the maximum applied force and D is the measurement of the diagonal of the mark left by the Indenter.

Participants

ENSAM (France. Contact: [email protected], [email protected], [email protected] and

[email protected]).

VTT (Finland. Contact: [email protected]).

Samples preparation

A preparation of the samples is necessary before the micro-indentation analysis. The samples were embedded in an acrylic resin KM-U so that the thickness could be analysed. Then a polishing step was performed to make the surface as smooth as possible. A polisher was used with different grits of abrasive paper: from 80 to 2400. After that, a mirror finish was obtained with a series of diamond pastes with particle sizes of 3 µm, 1µm, and finally ¼ µm.

Figure 13.2: Vickers-type point (a) and example of a fingerprint left by the indenter on the unaged PEEK (Courvoisier, 2017)

Sample (mod 6)

Figure 13.3: Mounted sample



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Protocol for micro-indentation measurements

The analyses were carried out using the Micro indentation Tester (MHT) of MSC Instrument (Figure 13.4). The selected indenter is a Vickers-type diamond tip with a pyramidal geometry (Figure 13.2). The force imposed is 150 mN, and the charge and discharge rates are 100 μm/min. A 30 second pause was made between the load and the discharge. The maximum depth of the tip during testing is 18 μm. The samples analysed are a cross section of the 0.5 mm thick plates, coated and polished. The indentations were made from one side to the other of the sample. The space between the centre of each indentation is equal to at least three times the size of the mark of the indenter on the material, in order to avoid any interference of measurement when measuring close to its neighbour.

Results obtained for unaged samples

The micro-indentation technique allowed the profiles of the elastic modulus to be obtained in the thickness of the samples. The following figures show the oxidation profile of a “mod 6” sample before aging. Three samples of the same material (mod 6-Tpe-UnA) were analysed to check the repeatability of measurements.

1

1.5

2

2.5

3

3.5

50 150 250 350 450 550

HV

IT

Thickness (µm)

100

200

300

400

500

600

50 150 250 350 450 550

EIT

(MP

a)

Thickness (µm)

Figure 13.5: Evolution of the hardness (a) and the modulus (b) according to the thickness.

Figure 13.4: Micro indentation Tester


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It could be noticed that the modulus is constant throughout the thickness of the sample. We can therefore consider that we have a homogeneous profile.

However, it would be necessary to make measurements on the surface of the sample to check that there is no skin effect.

References

Courvoisier, E. (2017). Analyse et modélisation cinétique du vieillissement thermique des matrices PEI et PEEK et ses conséquences sur l’absorption d’eau (Paris, ENSAM).

“Indentation, Software manual, CSM Instrument”.

Iqbal, T., Briscoe, B.J., and Luckham, P.F. (2011). Surface Plasticization of Poly(ether ether ketone). European Polymer Journal 47, 2244–2258.


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14 THz technique measurement protocol

Introduction

The samples were measured by a terahertz time-domain spectroscope in transmission mode as well as in reflection mode. In transmission mode the samples were located between an emitter and a detector with a distance of about 19cm between and a bandwidth up to 3 THz. In reflection mode the samples were placed perpendicular to the emitter and detector, which will be more important for a later application in NPPs where only one side access to a cable is available. The distance in this case is about 8.5cm and the bandwidth increases to 4.5 THz, due to a higher quality of the entire reflection system.

But in these tests only samples were measured which are in sheet or tape form and are assumed to be homogenous in their lateral shaping. Therefore, a mean A-Scan, which is the waveform along the axis of the electromagnetic waves through the sample, for every sample in every state can be calculated, analysed and saved. In the first step several features of this A-Scan were extracted, for example the time-of-flight, the peak magnitude and the pulse width. Out of this information the permittivity can be calculated, because of the hypothesis out of preliminary studies that the aging of these materials will be visible in permittivity changes in the terahertz domain.

In addition to the terahertz measurements, all samples and their permittivity were measured by an impedance analyser from 1 MHz up to 1 GHz, which results will also be shown.

The measurements of the cables will be provided later in this project, because of the issues to measure thin cable isolations inside the outer isolation. Especially coaxial cables will be hard to measure, because of their inner shielding, which prevents the electromagnetic waves to penetrate. That is why it is mandatory to find a strategy to measure those cables in reality at NPPs inside an electric cabinet with the condition to have a very small focus point that is smaller than the diameter of one isolated cable (current focus point is about several millimetres). A possible solution to measure it basically could be the placement of the reflection head next to the terminals, where the cables were connected to the terminal boards with a constant distance of 8.5cm and the guarantee to be placed perpendicular to the isolation surface. In order to solve the focusing issue other special optical lenses could be used to minimize the focusing point, where the electromagnetic waves impinge. To find such other lenses, further investigating has to be done before.

Results of the impedance analyser for unaged samples

The measurements were done with an impedance analyser by Keysight Technologies with a bandwidth of 1 MHz to 1 GHz, where the samples were placed in a special dielectric probe to measure permittivity with their real and imaginary part over frequency:


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The permittivities at 1Ghz for all samples were shown below, whereas the nomenclature of the x-axis is abbreviated with “Modification No.” - “Sheet” or ” Tape”:

Calculated permittivities in transmission mode

In transmission mode the permittivity can be calculated with the following formula:


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The permittivities for the unaged tapes in transmission mode are:

The permittivities for the unaged sheets in transmission mode are:

Calculated permittivities in reflection mode

In reflection mode the permittivity can be calculated with the following formula:

The permittivities for the unaged tapes in reflection mode are:


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The permittivities for the unaged sheets in reflection mode are:

Comparison of permittivities in reflection and transmission mode

The calculated permittivities in comparison show several differences:


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These differences are reasoned in the instability of the calculation for thin samples and the smaller

thickness of the tapes in comparison to the sheets (1mm thickness of the sheets, 0.5mm thickness of

the tapes). The thicker the samples are the more the electromagnetic waves interact with the material.

Furthermore, the tapes were not as flat as the sheets, which results in an arrangement of the reflection

head to the specific sample that is not always perpendicular.


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15 Isothermal TGA measurement protocol

Introduction

Thermogravimetric analysis (TGA) is a technique used to characterize a wide variety of polymers. TGA measures the amount and rate (velocity) of change in the mass of a sample as a function of temperature or time in a controlled atmosphere. The measurements are used primarily to determine the thermal and/or oxidative stabilities of materials as well as their compositional properties. The technique can analyze materials that exhibit either mass loss or gain due to decomposition, oxidation or loss of volatiles (such as moisture). It is especially useful for the study of polymeric materials, including thermoplastics, thermosets, elastomers, composites, films, fibers, coatings and paints. TGA measurements provide valuable information that can be used to select materials for certain end-use applications, predict product performance and aging.

Participants

INCT (contacts: [email protected], [email protected], [email protected]).

Sample preparation

The mass of samples should be between ten and twenty mg. To ensure reproducibility of the measurements, approximately the same sample weight should be used during each experiment. Dimensions of the sample should not exceed the diameter of the crucible. Surface area exposed of the purged gas shall be large to ensure efficient heat transfer.

Platinum crucible before each measurement is cleaned by burning organic remains using a laboratory burner and by dissolving inorganic residues in appropriate solvent. The sample shall not touch the thermocouple at the time of measurement.

Dynamic TGA test

Before the experiment, calibration of the instrument that covers balance calibration and temperature calibration shall be performed.

The Team Cables (TC) code sample is used as the sample name.

At the first stage of the experiment, dynamic TGA measurement is carried out. A sample of known weight is placed in an open platinum crucible and then inserted into the apparatus oven. The nitrogen flow rate through the balance is 40 ml/min.

The temperature changes in the range of 20 - 700oC. The programmable temperature increase is 10oC/min starting from ambient conditions. The measurement is conducted at an oxygen flow of 60 mL/min. Based on thermogravimetric data expressed as a percentage of initial weight versus temperature, the parameters of isothermal measurement are selected (temperature).

In the case of the monomodal thermal decomposition, the optimal temperature for the isothermal test is selected as an onset associated with to the main thermal effect observed in the thermogram.

Isothermal TGA test

TGA measurement according to the isothermal procedure allows to determine oxidative stability of materials. Two purged gases are required – inert gas (nitrogen) and oxidising gas (synthetic air). The sample is equilibrated at 35oC for 3 min. Then, in under nitrogen, the sample is heated at the rate of 50oC/min. The recommended temperature to which the polyethylene sample is heated is around 400oC. Then the purged gas is switched from nitrogen to synthetic air and heating is stopped. The rate


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of weight loss is a function of the earlier oxidation of the polymer. Sample is maintained under isothermal conditions until transition is completed. The test may require several scans to optimize run conditions. The sample is kept at the selected temperature for 150 min but correct parameters, particularly temperature and time, shall be selected experimentally.

Documentation and data analysis

The relationship between temperature or time and percentage of weight loss is referred to as a TGA

curve. The first derivative of the TGA curve (the DTG curve) is plotted to determine inflection points

useful for in-depth interpretations.

The dataset and spectra are stored and saved in a format compatible with Excel. The documentation

contains sample codes and measurement parameters necessary for further interpretation of the TGA

spectra.

The software TA Instrument Explorer is a program for controlling thermogravimetric analysis tests. The software TA Universal Analysis is used to analyse TGA spectra.

The time required to achieve the selected level of weight loss is correlated with the degree of oxidative degradation. The relationship between dose/temperature of aging and the time of weight loss can be used to monitor cable condition.

https://en.wikipedia.org/wiki/Curve

https://en.wikipedia.org/wiki/Derivative

https://en.wikipedia.org/wiki/Inflection_points


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16 SEM examination protocol

Introduction

Scanning electron microscopy (SEM) is a technique based on the principle of electron-matter interaction. Under the impact of the accelerated primary electron beam (ranging from 10 to 30 keV), backscattered electrons and secondary electrons emitted by the sample are collected selectively by detectors.

Using this technique, it is possible to observe mineral components, but also to identify their chemical composition when coupled with EDX Micro assay. This technique gives very high-resolution images.

In fact, this microscopic technique allows having information on the topography of the surfaces (using X-photons when collecting the emitted secondary electrons) but also on the distribution of atoms, which gives information on the chemical composition according to spatial distribution when backscattered electrons are collected. In our case, the microscopic analyses are performed on a slice of a sample containing ATH fillers and on particles obtained after TGA analysis.

Participants


[email protected]).

IRSN (France. contact: [email protected] and [email protected]).

Samples preparation

The samples were prepared as described below:

The insulation was embedded in a KM-CO resin (contains carbon particles) before being polished using MECAPOLP320 polishing machine with abrasive papers with increasing grain density from 80 to 2400 grains then a mirror finish was obtained with a series of diamond pastes with particle sizes of 3 µm, 1µm and finally ¼ µm.

The particles collected after ATG analysis were metallized to make their surface conductive, to allow the evacuation of electrons in order to avoid the accumulation of electrical charges on their surface (adverse effect on the image). Metallization was performed by depositing a fine layer of gold using a vacuum arc plasma.

Figure 16.1: Mounted sample

Protocol for SEM measurements

The analysis was performed on a HITACHI 4800 device. A beam of electrons accelerated by the voltage set according to the chemical nature of the polymer matrix to be analysed is sent on the surface of the

Sample (mod 5)




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sample. Electrons interact with matter, which produces a diffusion spectrum analysed by several sensors. The spectrum of secondary electrons gives the topology of the sample surface by imaging.

The backscattered electrons come from deeper layers of the sample and form a spectrum of another energetic band. It also allows observing the surface of the material even if the quality of the images is lower. In contrast, the analysis of the spectra of X-photons emitted by de-energized atoms gives access to the chemical composition of the sample.

Backscattered electrons

X-Photons

Secondary electrons

Sample

Figure16.2: SEM operating principle


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17 DMTA protocol

Dynamic mechanical thermal analysis (DMTA) yields information about the mechanical properties of a specimen placed in minor, usually sinusoidal, oscillation as a function of time and temperature by subjecting it to a small, usually sinusoidal, oscillating force.

With this method, mechanical stiffness (E´=storage modulus) and damping (E´´=loss modulus) over a wide range of temperatures and different frequencies can be measured. From the measured data E´ and E´´, Tg (glass transition point) can be calculated (Tg=E´´/E´). Tg values are characteristic to each and depend on the microstructure of viscoelastic materials. The samples can be analysed in different measurement (tension, bending, shear, compression) modes over a wide range of temperature (-150

C to +500 C) and frequency (0.001 - 1000 Hz). The equipment to be used is Mettler Toledo DMA/SDTA861.

Sample preparation

Sample preparation is depending on the mode of measurement. In this project, the most useful modes are tension and shear. When measuring the stiffness of materials, sample shape and dimensions must be rectangular or round. There are two possible clamping accessories, small and large. For shear mode only small clamping is possible. The rectangular sample dimensions for shear mode are thickness <6.5 mm, width <15 mm and length <18 mm. For round samples thickness <6.5 mm and diameter <15 mm. In tension mode the corresponding dimensions for small clamping accessory are thickness <2 mm, width <5 mm and length <9 mm. For large clamping accessory the possible sample dimensions are thickness <3 mm, width <7 mm and length 19.5 and 5.5 mm. Corresponding dimension of round samples are length 19.5 and 5.5 mm and diameter <3 mm.

Measuring protocol

When measuring the properties (stiffness and damping) of viscoelastic materials we must know the matrix for predicting the valid temperature gap to be used. From DSC data we can see the melting and sometimes also the glass transition temperatures. Normally the oscillation frequencies used are 1 and 10 Hz. Displacement amplitude and force are interpreted from linearity observation done before analysing.

Interpreting the results

The glass transition (Tg) is the temperature region where an amorphous material changes from a glassy phase to a rubbery phase upon heating, or vice versa if cooling. The glass transition is very important in polymer characterisation as the properties of a material are highly dependent on the relationship of the polymer end-use temperature to its Tg. For example, an elastomer will be brittle if its Tg is too high, and the upper use temperature of a rigid plastic is usually limited by softening at Tg. Hence, an accurate and precise measure of Tg is a prime concern to many plastics manufacturers and end use designers. The change of stiffness and Tg-temperature with loss factor are main values predicting the effect of exposure. Because the glass transition is a kinetic transition, it is strongly influenced by the frequency (rate) of testing. Therefore, as the frequency of the test increases, the molecular relaxations can only occur at higher temperatures and as a consequence, the Tg will increase with increasing frequency. In general, as the frequency increases, there will be a decrease in the intensity of the tan δ.


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Figure 17.1: Glass transition of an NR/SBR blend as a function of temperature at frequencies of 1 and 100 Hz. (From Thermal Analysis User Com 43, Mettler Toledo)


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18 Ultrasonic measurement protocol

The velocity of longitudinal waveform ultrasound can be theoretically linked to Young’s modulus, Poisson’s ratio and density (Kino, G. S., Acoustic waves: Devices, imaging & analog signal processing, Prentice-Hall Inc. 1987.). If the density can be assumed to remain constant during the ageing process, the changes in the longitudinal waveform velocity are caused by changes in elastic parameters: Young’s modulus and Poisson’s ratio.

The longitudinal waveform velocity is measured using traditional time-of-flight approach. This measurement approach requires two independent measurements: time-of-flight and acoustic-path-length measurements. The velocity is then defined by dividing the acoustic path length with the time of flight.

The time-of-flight is measured using 5 MHz contact transducer (GE 5 MHz .25B SC1418) with 22 mm long acrylic delay line. Water-based contact agent gel is used as acoustic coupling between the sample and the delay line (Figure 18.1). The time-of-flight is calculated from the measured signal (Figure 18.2. Dynaray Lite is used as a pulser-receiver. The thickness of the samples is used as the acoustic-path-length. The thicknesses are measured using digital micrometre (Mitutoyo MDC-1 SXF).

Figure 18.1: Measurement setup for time-of-flight.

Figure 18.2 Measured signal. Time-of-flight is defined as average of t1, t2 and t3.


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19 Conclusion

This study allowed the different laboratory partners involved in the TeaM Cables project to improve the knowledge and mastering of their own characterisation methods and measurement protocols in order to ensure the reliability of the results. In particular, "Round Robin Tests", allowed to compare and discuss the experimental results obtained by several laboratory partners with the same technique on the same materials.

Because of their robustness, these experimental results will be used to identify gaps in standards and, when possible, to propose ways of improvement of the characterisation methods and measurement protocols. In addition, these results will be integrated into a database for statistical analysis in order to help the identification of ageing markers but also to define the uncertainties and reproducibility of the different experimental techniques.

Finally, they will be used to check the validity of the multi-scale modelling tool that will be developed in the TeaM Cables project for predicting the lifetime of electric cables in service, but also to identify its different parameters.


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20 Annex 1: Results of Round Robin Tests on Dosimetry Measurements

Participants

IRSN (France, contact: [email protected]) INCT (Poland, contact: [email protected]) UJV (Czech Republic, contact: [email protected])

UJV dosimetry

Table 20.1: General information UJV

Country Czech Republic

Affiliation UJV Rez, a. s.

Address Hlavni 130, Rez, 250 68 Husinec

e-mail [email protected]

Tel. 00420266173579

Dosimeters used in the comparison (name) Alanine

Traceable to…. (name of reference lab) NPL (National Physical Laboratory, United Kingdom)

Calibration curve done at …….(date)*

* Our laboratory use several calibration curves according

to evaluated dose and dose range of calibration curves

6 July, 2013

13 May, 2016

22 February, 2018

23 February, 2018

Quality System operated in your lab ČSN EN ISO/IEC 17025:2005

Date of irradiation (specified by IRSN) 25 and 29 January, 2018

23 May, 2018

Date(s) of measurement(s) 22 – 23 February, 2018

15 – 20 June 2018

Remarks

Dosimeters with dose <10 Gy are in this dosimetry

system unmeasurable (below the lower limit of

evaluation)


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Table 20.2: UJV Dose measurement results – January 2018

Dosimeter position Dosimeter reference Irradiation duration Measured dose [kGy]

1A UP1A 5h 82.5 ± 2.7

2A UP2A 2h 30.06 ± 0.91

3A UP3A 1h 0.121 ± 0.008

UP3Abis 5h 0.776 ± 0.024

1B UP1B 7h 122.8 ± 3.7

2B UP2B 5h 77.9 ± 2.6

3B UP3B 5h 0.884 ± 0.032

UP3Bbis 7h 1.11 ± 0.04

- Control dosimeter - < 10 Gy

Table 20.3: UJV Dose measurement results – May 2018


4A

1

1h

14.5 ± 0.5

2 14.9 ± 0.5

3 15.0 ± 0.5

4

2h

30.0 ± 1.0

5 30.3 ± 1

6 30.6 ± 1

7 4h

61.8 ± 1.8

8 62.8 ± 1.8



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INCT dosimetry

Table 20.4: General information INCT

Country Poland

Affiliation Institute of Nuclear Chemistry and Technology

Address Dorodna 16, 03-195 Warsaw, Poland


[email protected]

Tel. (+48) 22 5041094


Traceable to…. (name of reference lab) Laboratory for Measurements of Technological

Doses, INCT

Calibration curve done at …….(date) 3 - 9 January, 2018

14 – 15 June 2018

Quality System operated in your lab -

Date of irradiation (specified by IRSN) 25 and 29 January, 2018

23 May, 2018

Date(s) of measurement(s) 23 – 27 February, 2018

11 – 14 June 2018

Remarks Alanine dosimeter is used to measure doses from about 20 Gy. For lower doses, hydroxyapatite or calcite is used as a dosimeter.

Table 20.5: INCT Dose measurement results – January 2018


1A P1A 5h 68.2 ± 1.0

2A P2A 2h 23.1 ± 0.2

3A P3A 1h 0.140 ± 0.002

P3Abis 5h 0.76 ± 0.01

1B P1B 7h 65.3 ± 1.7

2B P2B 5h 41.9 ± ± 0.6

3B P3B 5h 0.58 ± 0.02

P3Bbis 7h 0.78 ± 0.02



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Table 20.6: INCT Dose measurement results – May 2018


4A

1

1h

14.7 ± 0.5

2 14.5 ± 0.3

3 14.7 ± 0.3

4

2h

28.0 ± 1.0

5 28.8 ± 0.6

6 29.0 ± 0.3

7 4h

54.4 ± 1.3

8 54.7 ± 1.6


IRSN dosimetry

Table 20.7: General information IRSN

Country FRANCE

Affiliation IRSN

Address CEN Cadarache

IRSN/PSN-RES/SEREX/L2EC

Bat 328 - B.P. 3

13115 Saint Paul lez Durance - FRANCE


[email protected]

Tel. +33(0)4 42 19 92 34


Traceable to…. (name of reference lab) IONISOS ZI, 10500 Chaumesnil

Calibration curve done at …….(date) 15 March, 2017

Quality System operated in your lab -

Date of irradiation (specified by IRSN) 25 and 29 January 2018

23 May 2018

Date(s) of measurement(s) 26 – 31 January 2018

29 May, 2018


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Remarks -

Table 20.8: IRSN Dose measurement results – January, 2018


1A IP1A 5h 64.2 ± 2. 9

2A IP2A 2h 22.6 ± 1.0

3A IP3A 1h 1.4 ± 0.2

IP3Abis 5h 0.70 ± 0.05

1B IP1B 7h 78.1 ± 3.5

2B IP2B 5h 55.5 ± 2.5

3B IP3B 5h 0.60 ± 0.04

IP3Bbis 7h 0.88 ± 0.06


Table 20.9: IRSN Dose measurement results – May, 2018


4A

2 1h 13.9 ± 0.6

5 2h 27.3 ± 1.2

8 4h 54.9 ± 2.5


Discussion and conclusion

20.5.1 Summary of results

Table 20.10: Summary of dosimetry results

Dosimeter position

Irradiation duration

Measured dose [kGy] Standard deviations of measurements

UJV INCT IRSN

1A 5h 82.5 ± 2.7 68.2 ± 1.0 64.2 ± 2. 9 13.4%

2A 2h 30.06 ± 0.91 23.1 ± 0.2 22.6 ± 1.0 16.5%

3A 1h 0.121 ± 0.008 0.140 ± 0.002 0.14 ± 0.02 8.2%


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5h 0.776 ± 0.024 0.76 ± 0.01 0.70 ± 0.05 5.4%

1B 7h 122.8 ± 3.7 65.3 ± 1.7 78.1 ± 3.5 34.0%

2B 5h 77.9 ± 2.6 41.9 ± ± 0.6 55.5 ± 2.5 31.2%

3B 5h 0.884 ± 0.032 0.58 ± 0.02 0.60 ± 0.04 25.0%

7h 1.11 ± 0.04 0.78 ± 0.02 0.88 ± 0.06 18.3%

4

1h

14.5 ± 0.5 14.7 ± 0.5

13.9 ± 0.6 2.5% 14.9 ± 0.5 14.5 ± 0.3

15.0 ± 0.5 14.7 ± 0.3

2h

30.0 ± 1.0 28.0 ± 1.0

27.3 ± 1.2 4.2% 30.3 ± 1 28.8 ± 0.6

30.6 ± 1 29.0 ± 0.3

4h 61.8 ± 1.8 54.4 ± 1.3

54.9 ± 2.5 7.3% 62.8 ± 1.8 54.7 ± 1.6

20.5.2 Discussion

The results of the first series of dosimetry (January 2018, position 1, 2 and 3) show fairly large standard deviations between the results of different laboratories ranging from 5 to 34 %. These significant differences are due to problems of localization of the dosimeters in the irradiation chamber (superposition of the dosimeters) and therefore of distance to the source, another series of irradiation was conducted in May 2018 (position 4), being careful to position dosimeters compared between laboratories more appropriately (spider positioning). In this latter case the results are much more consistent, showing standard deviations below 8%, which is very acceptable for dosimetry measurements.


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21 Annex 2: Results of Round Robin Tests on Electrical Measurements

Participants

UNIBO (Italy. contact: [email protected])

UJV (Czech Republic. contact: [email protected])

Cable samples

Two sizes of cable sample were used for both cable types in the tests. Because all the partners use the Nexans project samples. In this Round Robin Test will be also used the project cable samples:

1) Coaxial cable. 50 Ohm 20 m

2) Coaxial cable. 50 Ohm 200 m

3) Twisted-pair cable 10 m

4) Twisted-pair cable 100 m

The length of the cable is only indicative.

Insulation resistance measurement results and discussion

Sample identification Coax. 200 m

Test instrument (model) Keithley model 248 high voltage supply +

Keithley 6514 system electrometer

Keithley, Model 6517B

Applied voltage (V) 500V

Configuration conductor / shielding

DUT/Ambient temperature 30 / 23 °C 31 ±1 / – °C

- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300

Rinsul [UNIBO] (GΩ)

1275 ± 4%

1920 ± 4%

4020 ± 4%

Rinsul [UJV] (GΩ)

2950

3100

4710 ±10%

Comments


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- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


560 ± 4%

800 ± 4%

1990 ± 4%

Rinsul [UJV] (GΩ)

1450

2270

4820 ±10%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


12750 ± 4%

19200 ± 4%

40190 ± 4%

Rinsul [UJV] (GΩ)

14600

24500

45700 ±10%

Comments


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- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


5620 ± 4%

8030 ± 4%

19930 ± 4%

Rinsul [UJV] (GΩ)

13200

20100

42200 ±10%

Comments







DUT/Ambient temperature 80 / 23 °C 79.5 ±1.5 / – °C

- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


23 ± 4%

24 ± 4%

32 ± 4%

Rinsul [UJV] (GΩ)

14.5

14.9

18.4 ±15%

Comments


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DUT/Ambient

temperature

80 / 23 °C 79.5 ±1.5 / – °C

- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


20 ± 4%

21 ± 4%

28 ± 4%

Rinsul [UJV] (GΩ)

11.9

12.2

15.6 ±15%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


230 ± 4%

245 ± 4%

320 ± 4%

Rinsul [UJV] (GΩ)

142

148

185 ±15%

Comments


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- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


200 ± 4%

210 ± 4%

280 ± 4%

Rinsul [UJV] (GΩ)

117

121

157 ±15%

Comments

Sample identification Twisted pair.10 m





Configuration A to B+shielding


- Orient Number

- Orient Number

- Orient Number

Time (s)

30

60

300


16.4 ± 4%

20.8 ± 4%

33.3 ± 4%

Rinsul [UJV] (GΩ)

14.0

18.8

51.2 ±15%

Comments


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Configuration B to A+shielding


- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


15.6 ± 4%

19.2 ± 4%

31 ± 4%

Rinsul [UJV] (GΩ)

13.3

18.2

57.3 ±15%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


17.7 ± 4%

21.2 ± 4%

35 ± 4%

Rinsul [UJV] (GΩ)

18.7

24.2

48.7 ±15%

Comments


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- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


20.2 ± 4%

27 ± 4%

50.5 ± 4%

Rinsul [UJV] (GΩ)

17.8

24.3

56.5 ±15%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


1.5 ± 4%

2.1 ± 4%

6.6 ± 4%

Rinsul [UJV] (GΩ)

1.39

1.9

5.28 ±15%

Comments








- Orient Number

- Orient Number

Time (s)

30

60


1.7 ± 4%

2.3 ± 4%

Rinsul [UJV] (GΩ)

1.45

1.92


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- Orient Number

- 300

6.7 ± 4% 5.74 ±15%

Comments






Configuration A to B+shieldingTemperature: 80°C


- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


2.8 ± 4%

3.7 ± 4%

8.1 ± 4%

Rinsul [UJV] (GΩ)

1.66

2.26

4.76 ±15%

Comments






Configuration B to A+shieldingTemperature: 80°C


- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


2.6 ± 4%

3.3 ± 4%

7.3 ± 4%

Rinsul [UJV] (GΩ)

1.46

2.03

4.88 ±15%

Comments






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- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


14.6 ± 4%

28.7 ± 4%

91 ± 4%

Rinsul [UJV] (GΩ)

14.8

27.5

80.8 ±10%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


16.8 ± 4%

33.1 ± 4%

94.3 ± 4%

Rinsul [UJV] (GΩ)

17.6

31.4

84.8 ±10%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


166.1 ± 4%

349.6 ± 4%

1020 ± 4%

Rinsul [UJV] (GΩ)

151

253

715 ±10%

Comments


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- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


183.1 ± 4%

316.4 ± 4%

925.9 ± 4%

Rinsul [UJV] (GΩ)

159

286

737 ±10%

Comments








- Orient Number

- Orient Number

- Orient Number

-

Time (s)

30

60

300


13.3 ± 4%

25 ± 4%

100 ± 4%

Rinsul [UJV] (GΩ)

17.8

32.7

93.0 ±10%

Comments








- Orient Number

- Orient Number

- Orient Number

Time (s)

30

60

300


13.3 ± 4%

27.02 ± 4%

111.1 ± 4%

Rinsul [UJV] (GΩ)

16.5

31.5

84.3 ±10%

Comments


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Capacitance measurement results and discussion


Test instrument (model) Novocontrol Alpha Dielectric Analyzer

Frequency 120 Hz. 1 kHz. 10 kHz

Configuration 30 °C

Ambient Temperature &

humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

1.82E-09 ± 1%

1.82E-09 ± 1%

1.82E-09 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

1.816E-09 ± 1%

1.816E-09 ± 1%

1.815E-09 ± 1%

Comments






humidity

23 °C. 65 %

Freq

120 Hz

- 1 kHz

C (F) [UNIBO]

1.83E-08 ± 1%

1.83E-08 ± 1%


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- Orient Number

- Orient Number

- Orient Number

- 10 kHz

1.84E-08 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

1.824E-08 ± 1%

1.824E-08 ± 1%

1.830E-08 ± 1%

Comments

Sample identification Twisted pair. 10 m





humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

6.13E-10 ± 1%

6.09E-10 ± 1%

6.06E-10 ± 1%

Comments


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humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

6.00E-10 ± 1%

5.94E-10 ± 1%

5.90E-10 ± 1%

Comments

Sample identification Twisted pair. 100m





humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

6.88E-09 ± 1%

6.81E-09 ± 1%

6.76E-09 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UNIBO]

6.83E-09 ± 1%

6.79E-09 ± 1%

6.76E-09 ± 1%

Comments


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Test instrument (model) LCR-meter Agilent U1732B



DUT and Ambient Temperature 23.7 ±0.7 °C

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UJV]

1.83E-09 ±1.7%

1.83E-09 ±1.4%

1.84E-09 ±2.7%

Comments






- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UJV]

1.83E-08 ±1.4%

1.83E-08 ±1.1%

1.84E-08 ±2.0%

Comments




Configuration conductor A / conductor B


- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UJV]

7.35E-10 ±2.2%

7.32E-10 ±1.5%

7.29E-10 ±2.7%

Comments


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Configuration conductor A / conductor B


- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

C (F) [UJV]

7.24E-09 ±1.5%

7.22E-09 ±1.1%

7.20E-09 ±2.0%

Comments

Tan delta measurement results and discussion






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

2.4E-04 ± 1%

3.7E-04 ± 1%

7.7E-04 ± 1%

Comments






humidity

23 °C. 65 %

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

3.8E-05 ± 1%

1.1E-04 ± 1%


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- Orient Number

- Orient Number

- Orient Number

-

2.9E-04 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

4.09E-04 ± 1%

6.5E-04 ± 1%

4.16E-03 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

1.18E-04 ± 1%

4.72E-04 ± 1%

4.00E-03 ± 1%

Comments





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humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

5.75E-03 ± 1%

4.22E-03 ± 1%

3.84E-03 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

6.009E-03 ± 1%

4.405E-03 ± 1%

4.624E-03 ± 1%

Comments






humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

1.225E-02 ± 1%

6.510E-03 ± 1%

3.424E-03 ± 1%

Comments


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humidity

23 °C. 65 %

- Orient Number

- Orient Number

- Orient Number

-

Freq

120 Hz

- 1 kHz

- 10 kHz

Tan delta

1.307E-02 ± 1%

6.935E-03 ± 1%

5.153E-03 ± 1%

Comments

S matrix measurement results and discussion

UNIBO measurement:

Sample № CoXL-LCa-RR-VNA-UNI; length of coaxial cable 199.84 m.

Frequency S-parameters

S12 (dB Mag) S12 (dB/100 m) S21 (dB Mag) S21 (dB/100 m)

1 MHz

10 MHz

100 MHz

500 MHz

1 GHz

Sample № CoXL-SCa-RR-VNA-UNI; length of coaxial cable 20.00 m.



1 MHz

10 MHz

100 MHz

500 MHz

1 GHz


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UJV measurement:

Sample № CoXL-LCa-RR-VNA-UJV; length of coaxial cable 199.84 m.



1.209 MHz 2.397 1.199 2.401 1.202

10.209 MHz 7.691 3.848 7.724 3.865

100.209 MHz 27.223 13.623 27.163 13.592

500.108 MHz 71.580 35.818 70.786 35.421

1 GHz 89.074 44.573 86.709 41.888

Sample № CoXL-SCa-RR-VNA-UJV; length of coaxial cable 20.00 m.



1.209 MHz 0.291 1.455 0.296 1.479

10.209 MHz 0.772 3.858 0.784 3.920

100.209 MHz 2.754 13.774 2.756 13.778

500.108 MHz 7.671 38.355 7.677 38.387

1 GHz 11.474 57.371 11.464 57.323

General conclusion on the electrical measurements

Electrical measurements were performed by two laboratories (UNIBO and UJV).

Due to different instrumentation used for measurements, small differences can be appreciated among results of the two laboratories.

Referring to the insulation resistance results, in particular, measured currents are very small and noise-affected in the coaxial cable configuration. This can lead to very difficult resistance value extrapolation since it can easily vary in the very short requested acquisition time.

For the twisted pair configuration UNIBO and UJV insulation resistance results are close each other.

Capacitance measurements showed that capacitance is not dependent on both frequency and temperature.

Tan Delta tests showed different behaviour depending on the analysed specimen. In particular, Tan Delta raises with temperature and decreases with frequency in Coaxial cables; on the contrary, in twisted pair configuration, tan delta raises with temperature and decreases with frequency.


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22 Annex 3: Results of Round Robin Tests on FTIR Measurements

Participants

ENSAM (France. contact: [email protected] and [email protected]) IRSN (France. contact: [email protected]) AMU (France. Contact : [email protected])

Test materials

1) Model silane crosslinked PE (Mod1-Tpe-RR-FTIR-…)

2) Twisted-pair cable filled XLPE insulation (TXLF-Sca-RR-FTIR-…)

3) Twisted-pair cable EVA/EPDM insulation (EVEP-Sca-RR-FTIR-…)

Model silane crosslinked PE (Mod1-Tpe-RR-OIT)

22.3.1 ATR mode

Figure 22.1: FTIR spectrum obtained by ENSAM for Mod1-Tpe (both faces of the sample) using ATR mode




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Figure 22.2: FTIR spectra obtained by IRSN (left) and AMU (right) for Mod1-Tpe (both faces of the sample: face 1 in red, face 2 in green) using ATR mode

22.3.2 Transmission mode

Figure 22.3: FTIR spectrum obtained by ENSAM for Mod1-Tpe using transmission mode

22.3.3 Peak attribution

Mod1 is a neat silane crosslinked PE. Its IR peaks observed by FTIR spectroscopy (ATR and transmission mode) are compiled in the following table:


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Table 22.1: FTIR peak attribution for Mod1-Tpe

Wavenumber (cm-1) Attribution

2916 C-H stretching

2848

1463 CH2 bending

1379 Symmetrical bending of CH3 groups

1305 C-CH3 bending

1190 Si-OC stretching

1090

1000-1030 Si-O-Si stretching

770-800 Si-C stretching

719 -(CH2)n- (n ≥ 4) rocking


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Twisted-pair cable filled XLPE insulation (TXLF-SCa)

22.4.1 ATR mode

Figure 22.5: FTIR spectra obtained by IRSN for TXLF-SCa (2 insulations: insulation n°3 in red, insulation n°4 in green) using ATR mode


TXLF is a silane crosslinked PE stabilized with a mixture of a phenolic antioxidant and a thioether antioxidant and filled with ATH (Aluminium Tri Hydrate). In the following table, only the additional peaks (compared to Mod1) are compiled:

Figure 22.4: FTIR spectrum obtained by ENSAM for TXLF-SCa (both faces of the sample) using ATR mode


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Table 22.2: FTIR peak attribution for TXLF-SCa


3639 OH stretching (phenol) (phenolic antioxidant)

3620

OH stretching (Al(OH)3)

(ATH filler)

3525

3440

3370

1734 C=O stretching (ester) (antioxidants)

1362

C-O stretching (ester)

(antioxidants) 1240

1168

1000 Al-O (AlO4) (ATH)

500-900 Al-O (AlO6) (ATH)


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Twisted-pair cable EVA/EPDM insulation (EVEP-Sca)

22.5.1 ATR mode

Figure 22.6: FTIR spectrum obtained by ENSAM for EVEP-SCa using ATR mode

Figure 22.7: FTIR spectrum obtained by IRSN (left) and AMU (right) for EVEP-SCa (2 insulations: insulation n°5 in red, insulation n°6 in green) using ATR mode


EVEP is an EVA/EPDM material. Its IR peaks observed by FTIR spectroscopy (ATR mode) are compiled in the following table:


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Table 22.3: FTIR peak attribution for EVEP-SCa


2917 C-H stretching

2848

1464 CH2 bending

1739 C=O stretching (ester) (EVA)

1371

C-O stretching (ester) (EVA)

1239

1020

719 -(CH2)n- (n ≥ 4) rocking

General conclusion on the FTIR measurements

For the different material samples under study, the three laboratories found IR absorption bands at exactly the same position (i.e. wavenumber) with similar intensities. These results validate the FTIR measurement protocol.

In addition, AMU performed principal component analysis (PCA) on the IRSN spectra (Figure 22.8) and on ENSAM spectra (Figure 22.9) separately because the numbers of points obtained with each FTIR spectrophotometer were not equivalent. The PCA results in Figure 22.8 show that the two samples (Mod1-TP- RR and TXLF-Sca-RR) are easily separated and identified. Identically, the PCA result in Figure 22.9 shows that the three samples (Mod1-TP- RR, and TXLF-Sca-RR and EVEP-Sca-RR) are easily separated.

Figure 22.8: PCA performed on the IRSN spectra


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Figure 22.9: PCA performed on the IRSN spectra

Mod1-Tpe-RR

EVEP-SCa-RR

TXLF-SCa-RR


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23 Annex 4: Results of Round Robin Tests on OIT Measurements

Participants

ENSAM (France. contact: [email protected] and [email protected]) IRSN (France. contact: [email protected] and [email protected]) UJV (Czech Republic: [email protected])

Test materials

1) Model silane crosslinked PE (Mod1-Tpe-RR-OIT-…)

2) One-pair cable filled XLPE insulation (OPTC-Sca-RR-OIT-…)

3) Twisted-pair cable unfilled XLPE insulation (TXLN-Sca-RR-OIT-…)

4) Twisted-pair cable filled XLPE insulation (TXLF-Sca-RR-OIT-…)

Model silane crosslinked PE (Mod1-Tpe-RR-OIT)

23.3.1 Results

Table 23.1: OIT measurements for Mod1-Tpe Remark: Data not available (N/A)

Summary Mod1-Tpe-RR-OIT ENSAM IRSN UJV

Measurement T [°C] method mass [mg] OIT [min] mass [mg] OIT [min] mass [mg] OIT [min]

a 190 tangent 5.28 36 8.8 69.1 5.44 31.17

b 190 tangent 5.86 40 9.6 66.3 5.72 28.36

c 190 tangent 5.61 44 8.9 59.6 5.49 26.74

d 190 tangent 5.92 37 N/A N/A N/A N/A

e 190 tangent 5.35 40 N/A N/A N/A N/A

f 190 tangent 5.82 39 N/A N/A N/A N/A

Mean±st.dev. 190 tangent 5.64 ± 0.27 39 ± 3 9.1 ± 0.5 65 ± 4.9 5.6 ± 0.12 28.8 ± 1.8

a 200 tangent 5.3 13 9.0 23.3 5.39 9.23

b 200 tangent 5.98 15 8.9 26.0 5.38 10.53

c 200 tangent 5.46 13 9.6 21.6 5.35 8.85

d 200 tangent 5.74 13 10.4 20.5 N/A N/A



Mean±st.dev. 200 tangent 5.43 ± 0.40 13 ± 1 9.5 ± 0.7 22.9 ± 2.4 5.4 ± 0.02 9.5 ± 0.7

a 210 tangent 5.60 4 7.7 8.6 5.28 3.53

b 210 tangent 5.44 5 8.2 7.8 5.14 4.27

c 210 tangent 5.59 4 8.5 5.8 5.12 3.63









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a 220 tangent 5.34 2 9.3 3.0 5.29 1.72

b 220 tangent 5.50 2 10.6 3.3 5.19 1.41

c 220 tangent 5.60 2 11.0 3.4 5.47 1.48





a 190 threshold 5.28 35 8.8 66.7 5.44 28.02

b 190 threshold 5.86 37 9.6 65.5 5.72 25.97

c 190 threshold 5.61 43 8.9 56.3 5.49 26.14

d 190 threshold 5.92 35 N/A N/A N/A N/A

e 190 threshold 5.35 38 N/A N/A N/A N/A

f 190 threshold 5.82 36 N/A N/A N/A N/A

Mean±st.dev. 190 threshold 5.64 ± 0.27 37 ± 3 9.1 ± 0.5 62.8 ± 5.7 5.6 ± 0.12 26.7 ± 0.9

a 200 threshold 5.3 12 9.0 21.1 5.39 6.93

b 200 threshold 5.98 14 8.9 24.1 5.38 8.51

c 200 threshold 5.46 12 9.6 19.0 5.35 7.46

d 200 threshold 5.74 12 10.4 18.1 N/A N/A




a 210 threshold 5.60 4 7.7 7.7 5.28 1.81

b 210 threshold 5.44 4 8.2 6.9 5.14 2.64

c 210 threshold 5.59 3 8.5 4.5 5.12 2.57





a 220 threshold 5.34 1 9.3 2.2 5.29 1.13

b 220 threshold 5.50 1 10.6 2.4 5.19 0.78

c 220 threshold 5.60 1 11.0 2.4 5.47 0.87





a 190 time to max. rate 5.92 45 8.8 81.4 5.44 40.67

b 190 time to max. rate 5.35 47 9.6 78.9 5.72 41.82

c 190 time to max. rate 5.82 47 8.9 76.2 5.49 41.46

Mean±st.dev. 190 time to max. rate 5.70 ± 0.30 46 ± 1 9.1 ± 0.5 78.8 ± 2.6 5.6 ± 0.12 41.3 ± 0.5

a 200 time to max. rate 5.74 17 9.0 28.7 5.39 14.84

b 200 time to max. rate 4.87 16 8.9 30.9 5.38 16.43

c 200 time to max. rate 5.2 16 9.6 27.1 5.35 14.35

d 200 time to max. rate N/A N/A 10.4 26.6 N/A N/A


a 210 time to max. rate 5.86 7 7.7 11.2 5.28 6.11


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b 210 time to max. rate 5.60 7 8.2 10.2 5.14 6.4

c 210 time to max. rate 5.32 7 8.5 8.2 5.12 6.14


a 220 time to max. rate 5.54 3 9.3 4.5 5.29 2.87

b 220 time to max. rate 5.22 3 10.6 4.3 5.19 2.54

c 220 time to max. rate 5.22 3 11.0 4.6 5.47 2.72


23.3.2 Arrhenius plots

OIT values obtained can be plotted in an Arrhenius graph (ln(OIT)=f(1/T)). For Mod1-Tpe, OIT seems to obey to Arrhenius law between 190°C and 220°C. It is possible to determine the activation energy by using the following equation:

ln(OIT) = ln(OIT0) + Ea

RT

Where OIT0 is a pre-exponential factor (expressed in s). Ea the activation energy (J.mol-1). R the perfect gas constant (8.314 J.mol-1.K-1). and T the temperature (K).

23.3.2.1 Tangent method

Table 23.2: Arrhenius parameters of Mod1-Tpe obtained by each partner using Tangent method

Tangent method Ea (kJ.mol-1) Ln(OIT0) (s)

ENSAM 192 ± 12 -42 ± 3

IRSN 186 ± 4 -41 ± 1

UJV 193 ± 6 -42 ± 2

Figure 23.1: Arrhenius plot of OIT for Mod1-Tpe using tangent method


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23.3.2.2 Threshold method

Table 23.3: Arrhenius parameters of Mod1-Tpe obtained by each partner using threshold method

Threshold method Ea (kJ.mol-1) Ln(OIT0) (s)

ENSAM 226 ± 12 -51 ± 3

IRSN 211 ± 3 -46 ± 1

UJV 216 ± 7 -49 ± 2

Figure 23.2: Arrhenius plot of OIT for Mod1-Tpe using threshold method

23.3.2.3 Time to reach maximum rate method

Table 23.4: Arrhenius parameters of Mod1-Tpe obtained by each partner using time to reach maximum rate method

Time to reach maximum rate method

Ea (kJ.mol-1) Ln(OIT0) (s)

ENSAM 171 ± 5 -37 ± 1

IRSN 183 ± 7 -39 ± 2

UJV 173 ± 3 -37 ± 1


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Figure 23.3: Arrhenius plot of OIT for Mod1-Tpe using time to reach maximum rate method

23.3.3 Discussion

For model silane crosslinked PE (Mod 1), whatever the method used to measure the OIT (tangent. threshold or time to maximum rate), the average OIT values determined by ENSAM. IRSN and UJV are extremely close. If looking at the corresponding Arrhenius parameters (in Tables 23.2, 23.3 and 23.4). it appears that the pre-exponential coefficients are identical. Only the activation energies are slightly different, but the maximum gap does not exceed 6.6% and remains in the order of magnitude of the maximum standard deviation. It can be thus concluded that there is few difference in the OIT measurement between the three laboratories.

One-pair cable filled XLPE insulation (OPTC-SCa-RR-OIT)

23.4.1 Results

Table 23.5: OIT measurements for OPTC-SCa.

Remark: Data not available (N/A). OPTC material was not initially selected for the project.

Summary OPTC-SCa-RR-OIT ENSAM IRSN UJV


a 225 tangent 5.60 76 N/A N/A 5.49 93.01

b 225 tangent 5.72 74 N/A N/A 5.35 98.46

c 225 tangent 4.68 75 N/A N/A 5.4 101.91

Mean±st.dev. 225 tangent 5.33 ± 0.57 75 ± 1 N/A N/A 5.4 ± 0.06 97.8 ± 3.7

a 230 tangent 5.40 45 N/A N/A 5.61 59.29

b 230 tangent 5.30 45 N/A N/A 5.64 61.15

c 230 tangent 5.70 43 N/A N/A 5.43 60.07


a 235 tangent 5.39 28 N/A N/A 5.59 32.98


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b 235 tangent 6.01 26 N/A N/A 5.59 32.71

c 235 tangent 5.60 26 N/A N/A 5.34 33.1


a 240 tangent 5.65 14 N/A N/A 5.19 19.67

b 240 tangent 5.83 14 N/A N/A 5.13 19.72

c 240 tangent 5.98 14 N/A N/A 5.19 19.52


a 245 tangent 6.54 10 N/A N/A 5.56 11.25

b 245 tangent 6.02 9 N/A N/A 5.08 11.24

c 245 tangent N/A N/A N/A N/A 5.58 11.37


a 225 threshold 5.60 69 N/A N/A 5.49 89.65

b 225 threshold 5.72 72 N/A N/A 5.35 94.56

c 225 threshold 4.68 75 N/A N/A 5.4 95.09

Mean±st.dev. 225 threshold 5.33 ± 0.57 72 ± 3 N/A N/A 5.4 ± 0.06 93.1 ± 2.4

a 230 threshold 5.40 43 N/A N/A 5.61 57.14

b 230 threshold 5.30 45 N/A N/A 5.64 59.99

c 230 threshold 5.70 41 N/A N/A 5.43 57.42


a 235 threshold 5.39 28 N/A N/A 5.59 33.03

b 235 threshold 6.01 25 N/A N/A 5.59 31.54

c 235 threshold 5.60 26 N/A N/A 5.34 33.29


a 240 threshold 5.65 12 N/A N/A 5.19 19.43

b 240 threshold 5.83 12 N/A N/A 5.13 19.29

c 240 threshold 5.98 13 N/A N/A 5.19 19.05


a 245 threshold 6.54 9 N/A N/A 5.56 10.82

b 245 threshold 6.02 9 N/A N/A 5.08 10.28

c 245 threshold N/A N/A N/A N/A 5.58 10.7


a 225 time to max. rate 5.60 85 N/A N/A 5.49 108.74

b 225 time to max. rate 5.72 86 N/A N/A 5.35 106.63

c 225 time to max. rate 4.68 85 N/A N/A 5.4 110.35

Mean±st.dev. 225 time to max. rate 5.33 ± 0.57 85 ± 1 N/A N/A 5.4 ± 0.06 108.6 ± 1.5








Mean±st.dev. 235 time to max. rate 5.67 ± 0.32 30 ± 3 N/A N/A 5.5 ± 0.12 39 ± 0.9




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c 245 time to max. rate N/A N/A N/A N/A 5.58 12.95

Mean±st.dev. 245 time to max. rate 6.28 ± 0.37 10 ± 1 N/A N/A 5.4 ± 0.23 12.9 ± 0


OIT values obtained can be plotted in an Arrhenius graph (ln(OIT)=f(1/T)). For OPTC-SCa, OIT seems to obey to Arrhenius law between 225°C and 245°C. It is possible to determine the activation energy by using the following equation:


RT

Where OIT0 is a pre-exponential factor (expressed in s), Ea the activation energy (J.mol-1), R the perfect gas constant (8.314 J.mol-1.K-1) and T the temperature (K).


Table 23.6: Arrhenius parameters of OPTC-SCa obtained by each partner using tangent method


ENSAM 226 ± 8 -46 ± 2

UJV 233 ± 4 -48 ± 1

Figure 23.4: Arrhenius plot of OIT for OPTC-SCa using tangent method


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Table 23.7: Arrhenius parameters of OPTC-SCa obtained by each partner using threshold method


ENSAM 230 ± 16 -47 ± 2

UJV 234 ± 7 -48 ± 2

Figure 23.5: Arrhenius plot of OIT for OPTC-SCa using threshold method


Table 23.8: Arrhenius parameters of OPTC-SCa obtained by each partner using time to reach maximum rate method



ENSAM 233 ± 5 -48 ± 1

UJV 229 ± 5 -46 ± 1


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Figure 23.6: Arrhenius plot of OIT for OPTC-SCa using time to reach maximum rate method

23.4.3 Discussion

For one-pair cable filled XLPE insulation (OPTC), whatever the method used to measure the OIT (tangent. threshold or time to maximum rate), the average OIT values determined by ENSAM and UJV are extremely close. If looking at the corresponding Arrhenius parameters (in Tables 23.6, 23.7 and 23.8). it appears that the pre-exponential coefficients are identical. Only the activation energies are slightly different, but the maximum gap does not exceed 3.0% and remains in the order of magnitude of the maximum standard deviation. It can be thus concluded that there is few difference in the OIT measurement between the two laboratories.

Twisted-pair cable unfilled XLPE insulation (TXLN-SCa-RR-OIT)

23.5.1 Results

Table 23.9: OIT measurements for TXLN-SCa.

Remarks: i) Data not available (N/A); ii) DSC thermogram displaying a double peak or a main peak with a well-marked shoulder, thus preventing the application of the threshold method (Uns).

Summary TXLN-SCa-RR-OIT ENSAM IRSN UJV


a 220 tangent 4.83 117 5.1 113.7 N/A N/A

b 220 tangent 5.58 130 5.1 113.2 N/A N/A

c 220 tangent 5.48 118 N/A N/A N/A N/A

Mean±st.dev. 220 tangent 5.30 ± 0.41 122 ± 7 5.1 ± 0 113.5 ± 0.4 N/A N/A

a 225 tangent 4.99 61 6.3 84.6 5.67 86.46

b 225 tangent 5.68 68 5.3 87.2 5.74 88.23

c 225 tangent 4.88 66 5.5 81.8 5.77 87.05



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a 230 tangent 5.55 39 5.6 40.3 5.64 49.38

b 230 tangent 4.56 44 5.3 44.2 5.48 49.51

c 230 tangent 4.60 41 5.8 40.4 5.57 51.95


a 235 tangent 5.42 19 5.5 29.7 5.26 29.04

b 235 tangent 5.12 26 5.6 29.4 5.2 27.1

c 235 tangent 5.04 23 5.2 25.7 5.32 27.14


a 227.5 tangent N/A N/A N/A N/A 5.5 66.18

b 227.5 tangent N/A N/A N/A N/A 5.53 67

c 227.5 tangent N/A N/A N/A N/A 5.23 64.72

Mean±st.dev. 227.5 tangent N/A N/A N/A N/A 5.4 ± 0.13 66 ± 0.9

a 232.5 tangent N/A N/A N/A N/A 5.29 34.7

b 232.5 tangent N/A N/A N/A N/A 5.08 36.7

c 232.5 tangent N/A N/A N/A N/A 5.27 36

Mean±st.dev. 232.5 tangent N/A N/A N/A N/A 5.2 ± 0.09 35.8 ± 0.8

a 220 threshold 4.83 116 5.1 Uns N/A N/A

b 220 threshold 5.58 123 5.1 Uns N/A N/A

c 220 threshold 5.48 116 N/A Uns N/A N/A

Mean±st.dev. 220 threshold 5.30 ± 0.41 118 ± 4 5.1 ± 0 Uns N/A N/A

a 225 threshold 4.99 56 6.3 Uns 5.67 80.04

b 225 threshold 5.68 66 5.3 Uns 5.74 84.99

c 225 threshold 4.88 65 5.5 Uns 5.77 83.96

Mean±st.dev. 225 threshold 5.18 ± 0.43 62 ± 6 5.7 ± 0.5 Uns 5.7 ± 0.04 83 ± 2.1

a 230 threshold 5.55 38 5.6 Uns 5.64 43.02

b 230 threshold 4.56 43 5.3 Uns 5.48 47.72

c 230 threshold 4.60 39 5.8 Uns 5.57 50.43

Mean±st.dev. 230 threshold 4.90 ± 0.56 40 ± 3 5.6 ± 0.2 Uns 5.6 ± 0.07 47.1 ± 3.1

a 235 threshold 5.42 16 5.5 Uns 5.26 26.75

b 235 threshold 5.12 24 5.6 Uns 5.2 24.06

c 235 threshold 5.04 22 5.2 Uns 5.32 25.75

Mean±st.dev. 235 threshold 5.19 ± 0.20 21 ± 4 5.5 ± 0.2 Uns 5.3 ± 0.05 25.5 ± 1.1

a 227.5 threshold N/A N/A N/A Uns 5.5 60.34

b 227.5 threshold N/A N/A N/A Uns 5.53 62.56

c 227.5 threshold N/A N/A N/A Uns 5.23 61.34

Mean±st.dev. 227.5 threshold N/A N/A N/A Uns 5.4 ± 0.13 61.4 ± 0.9

a 232.5 threshold N/A N/A N/A Uns 5.29 29.95

b 232.5 threshold N/A N/A N/A Uns 5.08 33.56

c 232.5 threshold N/A N/A N/A Uns 5.27 34.36

Mean±st.dev. 232.5 threshold N/A N/A N/A Uns 5.2 ± 0.09 32.6 ± 1.9

a 220 time to max. rate 4.83 123 5.1 121.5 N/A N/A

b 220 time to max. rate 5.58 134 5.1 117.4 N/A N/A

c 220 time to max. rate 5.48 125 N/A N/A N/A N/A

Mean±st.dev. 220 time to max. rate 5.30 ± 0.41 127 ± 6 5.1 ± 0 119.4 ± 2.9 N/A N/A

a 225 time to max. rate 4.99 68 6.3 92.1 5.67 91.2


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b 225 time to max. rate 5.68 73 5.3 90.4 5.74 91.93

c 225 time to max. rate 4.88 72 5.5 93.8 5.77 90.95


a 230 time to max. rate 5.55 43 5.6 48.3 5.64 51.77

b 230 time to max. rate 4.56 47 5.3 48.4 5.48 54.24

c 230 time to max. rate 4.60 45 5.8 45.0 5.57 55.81


a 235 time to max. rate 5.42 21 5.5 32.8 5.26 30.91

b 235 time to max. rate 5.12 28 5.6 31.7 5.2 29.14

c 235 time to max. rate 5.04 26 5.2 29.1 5.32 29.24


a 227.5 time to max. rate N/A N/A N/A N/A 5.5 69.27

b 227.5 time to max. rate N/A N/A N/A N/A 5.53 69.89

c 227.5 time to max. rate N/A N/A N/A N/A 5.23 68.51

Mean±st.dev. 227.5 time to max. rate N/A N/A N/A N/A 5.4 ± 0.13 69.2 ± 0.6

a 232.5 time to max. rate N/A N/A N/A N/A 5.29 37.12

b 232.5 time to max. rate N/A N/A N/A N/A 5.08 38.71

c 232.5 time to max. rate N/A N/A N/A N/A 5.27 38.84

Mean±st.dev. 232.5 time to max. rate N/A N/A N/A N/A 5.2 ± 0.09 38.2 ± 0.8


OIT values obtained can be plotted in an Arrhenius graph (ln(OIT)=f(1/T)). For TXLN-SCa, OIT seems to obey to Arrhenius law between 220°C and 235°C. It is possible to determine the activation energy by using the following equation:


RT

Where OIT0 is a pre-exponential factor (s). Ea the activation energy (J.mol-1). R the perfect gas constant (8.314 J.mol-1.K-1). and T the temperature (K).


Table 23.10: Arrhenius parameters of TXLN-SCa obtained by each partner using tangent method


ENSAM 228 ± 9 -47 ± 2

IRSN 203 ± 23 -41 ± 6

UJV 244 ± 6 -50 ± 1


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Figure 23.7: Arrhenius plot of OIT for TXLN-SCa using tangent method


Table 23.11: Arrhenius parameters of TXLN-SCa obtained by each partner using threshold method


ENSAM 234 ± 12 -48 ± 3

UJV 252 ± 8 -52 ± 2

Figure 23.8: Arrhenius plot of OIT for TXLN-SCa using threshold method


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Table 23.12: Arrhenius parameters of TXLN-SCa obtained by each partner using time to reach maximum rate method



ENSAM 222 ± 8 -45 ± 2

IRSN 195 ± 23 -39 ± 5

UJV 239 ± 7 -49 ± 2

Figure 23.9: Arrhenius plot of OIT for TXLN-SCa using time to reach maximum rate method

23.5.3 Discussion

For twisted-pair cable unfilled XLPE insulation (TXLN), whatever the method used to measure the OIT (tangent. threshold or time to maximum rate), the average OIT values determined by ENSAM and UJV are extremely close. If looking at the corresponding Arrhenius parameters (in Tables 23.10, 23.11 and 23.12), it appears that the pre-exponential coefficients and activation energies are slightly different but the maximum gap does not exceed 8.1% and 7.1% respectively and remains in the order of magnitude of the maximum standard deviation. It can be thus concluded that there is no difference in the OIT measurement between the two laboratories.

IRSN seems to have found quite different values of pre-exponential coefficients and activation energies than ENSAM and UJV. But, if looking at the corresponding Arrhenius graphs (in Figures 23.7 and 23.9), we can see that the OIT values determined by IRSN are randomly placed on the ENSAM and UJV’s Arrhenius straight-lines which explains this apparent difference. It can be finally concluded that there is few difference in the OIT measurement between the three laboratories.


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Twisted-pair cable filled XLPE insulation (TXLF-SCa-RR-OIT)

23.6.1 Results

Table 23.13: OIT measurements for TXLF-SCa. Remarks: i) Data not available (N/A); ii) DSC thermogram displaying a double peak or a main peak

with a well-marked shoulder. thus preventing the application of the threshold method (Uns).

Summary TXLF-SCa-RR-OIT ENSAM IRSN UJV


a 220 tangent 4.75 65 N/A N/A Uns Uns

b 220 tangent 5.45 74 N/A N/A Uns Uns

c 220 tangent 4.63 68 N/A N/A Uns Uns

Mean±st.dev. 220 tangent 4.94 ± 0.44 69 ± 5 N/A N/A Uns Uns

a 225 tangent 5.69 39 6.1 65.9 Uns Uns

b 225 tangent 6.38 38 5.8 64.8 Uns Uns

c 225 tangent 5.99 40 5.1 55.3 Uns Uns

Mean±st.dev. 225 tangent 6.02 ± 0.35 39 ± 1 5.6 ± 0.5 62.0 ± 5.8 Uns Uns

a 230 tangent 5.84 18 5.5 29.8 Uns Uns

b 230 tangent 5.76 19 5.4 30.9 Uns Uns

c 230 tangent 5.90 18 5.5 26.7 Uns Uns


a 235 tangent 5.52 10 5.3 16.0 Uns Uns

b 235 tangent 5.29 10 5.7 16.0 Uns Uns

c 235 tangent 5.72 9 5.4 15.4 Uns Uns


a 220 threshold 4.75 61 N/A Uns Uns Uns

b 220 threshold 5.45 72 N/A Uns Uns Uns

c 220 threshold 4.63 65 N/A Uns Uns Uns

Mean±st.dev. 220 threshold 4.94 ± 0.44 66 ± 6 N/A Uns Uns Uns

a 225 threshold 5.69 37 6.1 Uns Uns Uns

b 225 threshold 6.38 37 5.8 Uns Uns Uns

c 225 threshold 5.99 39 5.1 Uns Uns Uns

Mean±st.dev. 225 threshold 6.02 ± 0.35 38 ± 1 5.6 ± 0.5 Uns Uns Uns









a 220 a 4.75 71 N/A N/A Uns Uns

b 220 b 5.45 77 N/A N/A Uns Uns

c 220 c 4.63 75 N/A N/A Uns Uns

Mean±st.dev. 220 Mean±st.dev. 4.94 ± 0.44 74 ± 3 N/A N/A Uns Uns


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a 225 a 5.69 41 6.1 73.3 Uns Uns

b 225 b 6.38 41 5.8 67.9 Uns Uns

c 225 c 5.99 43 5.1 61.5 Uns Uns

Mean±st.dev. 225 Mean±st.dev. 6.02 ± 0.35 42 ± 1 5.6 ± 0.5 67.5 ± 5.9 Uns Uns

a 230 a 5.84 20 5.5 34.2 Uns Uns

b 230 b 5.76 21 5.4 35.1 Uns Uns

c 230 c 5.90 20 5.5 29.5 Uns Uns


a 235 a 5.52 11 5.3 17.6 Uns Uns

b 235 b 5.29 12 5.7 17.8 Uns Uns

c 235 c 5.72 11 5.4 17.0 Uns Uns



OIT values obtained can be plotted in an Arrhenius graph (ln(OIT)=f(1/T)). For TXLF-SCa, OIT seems to obey to Arrhenius law between 220°C and 235°C. It is possible to determine the activation energy by using the following equation:


RT

Where OIT0 is a pre-exponential factor (s), Ea the activation energy (J.mol-1), R the perfect gas constant (8.314 J.mol-1.K-1) and T the temperature (K).


Table 23.14: Arrhenius parameters of TXLF-SCa obtained by each partner using tangent method


ENSAM 274 ± 12 -58 ± 3

IRSN 288 ± 16 -61 ± 4


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Figure 23.10: Arrhenius plot of OIT for TXLF-SCa using tangent method


Table 23.15: Arrhenius parameters of TXLF-SCa obtained by each partner using threshold method


ENSAM 282 ± 14 -61 ± 3

Figure 23.11: Arrhenius plot of OIT for TXLF-SCa using threshold method


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Table 23.16: Arrhenius parameters of TXLF-SCa obtained by each partner using time to reach maximum rate method



ENSAM 269 ± 10 -57 ± 2

IRSN 284 ± 9 -60 ± 2

Figure 23.12: Arrhenius plot of OIT for TXLF-SCa using time to reach maximum rate method

23.6.3 Discussion

For model twisted-pair cable filled XLPE insulation (TXFL), whatever the method used to measure the OIT (tangent. threshold or time to maximum rate), the average OIT values determined by ENSAM and IRSN are extremely close. If looking at the corresponding Arrhenius parameters (in Tables 23.14, 23.15 and 23.16). It appears that the pre-exponential coefficients and the activation energies are slightly different but the maximum gap does not exceed 5.0% and 5.2% respectively and remains in the order of magnitude of the maximum standard deviation. It can be thus concluded that there is few differences in the OIT measurement between the two laboratories.

General conclusion on the OIT measurements

For the different material samples under study, the three laboratories found very close OIT values. These results validate the OIT measurement protocol.

In addition, AMU performed principal component analysis (PCA) on 3 OIT values obtained by each laboratory at each temperature for the three samples. The OIT data obtained for Mod1-Tpe-RR (Figure 23.13) are classified as a function of the temperature. Temperature increases while OIT1, OIT2 and OIT3 decrease.


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Figure 23.13: PCA obtained on Mod1-Tpe-RR-OIT at each temperature

PCA on the Mod1-Tpe-RR-OIT data at 190°C (figure 23.14) shows a good repeatability for each laboratory and a dispersion of mean laboratories results. Values obtained by IRSN are higher than those obtained by the other laboratories, UJV obtains the lower values.

Figure 23.14: PCA obtained on Mod1-Tpe-RR-OIT at 190°C

The OIT data obtained for TXLF-SCa-RR (figure 23.15) are classified as a function of the temperature. Temperature increases while OIT1, OIT2 and OIT3 decrease.

IRSN

ENSAM

UJV


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Figure 23.15: PCA obtained on TXLF-SCa-RR

The OIT data obtained for TXLF-SCa-RR are classified as a function of the temperature. Temperature increases while OIT1, OIT2 and OIT3 decrease. In this case, there is an overlay between 227°C (UJV) and 225°C (ENSAM).

Figure 23.16: PCA obtained on TXLN-SCa-RR-OIT data

Temperature

220°C225°C235°C 230 °C

Temperature

220°C225°C232,5°C 230 °C 227 °C235°C


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PCA results obtained on the TXLN-SCa-RR-OIT data at 225°C show a good repeatability for IRSN and UJV laboratories and a higher dispersion for ENSAM.

Figure 23.17: PCA obtained on TXLN-SCa-RR-OIT data at 225°C

OIT measurements were performed by three laboratories (ENSAM. IRSN. UJV) on various materials following the experimental protocols defined in the main part of this report. The comparison of the results for all these measurements shows a good consistency between the three laboratories and thus, validates the experimental protocols.

References

Ahmed. G.S.. Gilbert. M.. Mainprize. S.. and Rogerson. M. (2009). FTIR analysis of silane grafted high density polyethylene

Larché. J.-F.. Gallot. G.. Boudiaf-Lomri. L.. Poulard. C.. Duemmler. I.. and Meyer. M. (2014). Evidence of surface accumulation of fillers during the photo-oxidation of flame retardant ATH filled EVA used for cable applications. Polymer Degradation and Stability 103. 63–68

Miroslav Pastorek (2014). Crosslinking and ageing of ethylene-vinyl silane copolymers. Tomas Bata University

Oliveira. G.L.. and Costa. M.F. (2010). Optimization of process conditions. characterization and mechanical properties of silane crosslinked high-density polyethylene. Materials Science and Engineering: A 527. 4593–4599

Stuart. B.H. (2004). Infrared Spectroscopy: Fundamentals and Applications (John Wiley & Sons)

Vasconcelos. D.C.L.. Nunes. E.H.M.. and Vasconcelos. W.L. (2012). AES and FTIR characterization of sol–gel alumina films. Journal of Non-Crystalline Solids 358. 1374–1379

ENSAM

ENSAM

ENSAM

IRSN

IRSN IRSN

UJV

UJV

UJV


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24 Annex 5: Results of Round Robin Tests on EaB Measurements


These experimental measurements were conducted according to the experimental protocols defined in the main part of this document. Round robin tests were conducted by VTT/Finland and UJV/Czech Republic and the results are presented in the following section.

Test materials

The test materials included:

1) Coaxial short cable core tubular sample – CoXL-Sca[core]-RR-EaB-UJV/VTT

2) Single pair cable OPTC core 1 tubular sample – OPTC-Sca[core1]-RR-EaB-UJV/VTT

3) Single pair cable OPTC core 2 tubular sample – OPTC-Sca[core2]-RR-EaB-UJV/VTT

4) Model silane crosslinked PE – Mod1-DuB-RR-EaB-UJV/VTT

5) Coaxial short cable dumbell jacket 1 – CoXL-Sca[jacket]-RR-EaB-UJV/VTT

6) Single pair cable OPTC jacket – OPTC-Sca[jacket]-RR-EaB-UJV/VTT

The sample codes deviate from the sample codes listed in RR-procedure.

Results

The results of RRTs are presented in the following table. The used acceptance criterion was agreed to be

a) either the difference of individual medians of measured EaB values by UJV and VTT (ΔεtB = |εtB1 – εtB2|) divided by their mean value (εt̅B = (εtB1 + εtB2)/2) has to be ≤ 10 %;

b) or the intersection of both 95.4-% confidence intervals around the individual medians has not to be empty set.

The criterion specified in paragraph (a) above was always fulfilled.

For comparison (not as part of RRT), Nexans conducted testing on OPTC (single pair cable) samples according to standard IEC 60811-501 and reported results to be 233% for insulation and 174% for sheath. For coaxial cable Nexans reported EaB values of 422% for insulator and 178% for sheath. Only the core insulation EaB values (for tubular samples) from Nexans are fully comparable to RRT results presented since the differences in sample geometries.

Table 24.1: Overview of elongation-at-break results, evaluation of acceptance criterion (a)

Elongation at Break, [%] Acceptance criterion (24.3.a)

(UJV vs. VTT)

Sample/Specimen UJV VTT (ΔεtB/εt̅B) ≤ 0.1

Team Cable RRT ID Specimen type median

ar. mean

st. dev. median

ar. mean

st. dev. ΔεtB εt̅B ΔεtB/εt̅B

CoXL-Sca[core]-RR-EaB-UJV/VTT

tubular, nominal

EaB 501 494 ± 33 472 468 ± 15 29 486.5 0.060

OPTC-Sca[core1]-RR-EaB-UJV/VTT

tubular, nominal

EaB 245 241 ± 11 237 239 ± 22 8 241 0.033


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OPTC-Sca[core2]-RR-EaB-UJV/VTT

tubular, nominal

EaB 265 268 ± 13 289 287 ± 31 24 277 0.087

Mod1-DuB-RR-EaB-UJV/VTT dumb-bell,

nominal EaB

349 336 ± 45 343 332 ± 63 6 346 0.016

CoXL-Sca[jacket]-RR-EaB-UJV/VTT

dumb-bell, nominal

EaB 96.8 96.3 ± 5.7 96 97 ± 7 0.8 96.4 0.009

OPTC-Sca[jacket]-RR-EaB-UJV/VTT

dumb-bell, nominal

EaB 117 116 ± 7.3 108 109 ± 6 9 112.5 0.080

Figure 24.1: Median EaB values (UJV and VTT) or arithm. mean values (Nexans) compared altogether and provided by the 95.4-% confidence intervals (i.e. by two standard deviations of measurements) serving for graphical evaluation of acceptance criterion (b): The intersection of both (UJV and VTT)

95.4-% confidence intervals around the individual medians of EaB values has not to be an empty set.

General conclusion on the EaB measurements

The comparison of the results for all these measurements shows that the acceptance criterion (a) is fulfilled and thus the experimental protocol can be considered as validated.

0

100

200

300

400

500

600

700

Elo

nga

tio

n a

t bre

ak [%

]

Comparison of elongation-at-break values for Round Robin Test

UJV VTT Nexans

Documents

Deliverable D3.2: Measurement protocols · Deliverable D3.2: Measurement protocols WP3: Cable and materials characterisations Grant Agreement number: 755183 NFRP-2016-2017-1 Euratom