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NMR as a Versatile Tool in the Study of Polymer Aging
Alina Adams ITMC, RWTH Aachen University
Problems around Marine Aging of Polymers
Marine aging is due to the effect of pressure, saline water ingress, UV action, temperature ….
In order to establish water profiles in marine components modelling is
necessary, but the validity and limits of these models need to be addressed. Need of more realistic experimental test facilities and improved models of
the mechanical response. Proper lifetime prediction requires the knowledge of the changes at the
molecular level leading to failure. Depth-dependent measurements of the water ingress to validate and
improve the existing models.
Application of non-destructive analytical tools for in-situ condition monitoring. 2
NMR of Polymers @ ITMC RWTH Aachen
700 MHz
20 MHz
Spectroscopy
Relaxation
Imaging
Diffusion
Structure and morphology of polymers in solid state
Composite materials
Morphology of nanocomposites
Condition monitoring and aging of polymers
Interaction of polymers with liquids
Non-destructive quality control by
compact NMR
NMR methodology
RF-Spule
0B
0B
M0B
M
1B
Radio-frequency coil to generate the B1 field
4
NMR: Comunication in Magnetic Fields
NMR spectrum determined by the chemical structure
CH3
CH2
2:6
Relaxation decay determined by the molecular mobility / morphology
Time t
1H NMR
NMR of Solid Polymers
700 MHz
Bulk Relaxometry, Diffusometry, and Spectroscopy by High-Field NMR
Non-Destructive Depth-Dependent Relaxometry and Diffusometry by Compact Single-Sided NMR
Measuring spot
Radiofrequency coil
Permanent magnets
20 MHz
Sample
A. Adams, Trends Anal. Chem., 83, 107-119 (2016) A. Adams, Magn. Reson. Imaging 56, 119–125 (2019) 5
NMR-MOUSE (Mobile Universal Surface Explorer)
Principle of the Measurement
6
Principle of the Measurement
The decay is determined by the molecular
mobility
Non-Destructive Morphological Studies of Large Objects With the NMR-MOUSE
A. Adams and B. Blümich, Macromol. Symp. 327(1), 29-38 (2013) 8
Dedicated and Portable Low-Field NMR Equipment
9
Measurement of Biofilms in Yellowstone National Park
Equipment
Experimental Setup
PM5 NMR-MOUSE
Measurement of Frescos in Ostia, Italy
Equipment
Experimental Setup
PM25 NMR-MOUSE
log (Storage time)
log
(Hoo
p S
tress
)
Stage I Ductile failure
Stage II Brittle failure
log (Storage time)
log
(Hoo
p S
tress
)
Stage I Ductile failure
Stage III Total failure
Stage II Brittle failure
Controlled water pressure
Controlled water
temperature
Aging of Polyethylene Pipes under Hydrostatic Pressure and at Elevated Temperatures
Hydrostatic pressure tests are the most frequently used laboratory tests to predict the life time of a polymer pipe 50-100 years
often questioned about their relevance to field aging very long testing times the changes of the molecular network
during the various aging stages are largely unknown
80 °C
10
PE100
PEHD
Morphological Changes with the Storage Time
N. Sun, M. Wenzel, and A. Adams, Polymer, 55, 3792-3800 (2014)
According to the literature:
The morphological changes are due to annealing and hydrostatic pressure.
The theoretical density of tie-molecules fails to describe the behavior of PE100 and PEHD.
Minor Major
crystalline phase
amorphous phase
interface
tie-molecule
Li L
The density of tie-molecules is the main factor for controlling the long term behavior of PE-pipes.
Reduction in m
obility R
eduction in mobility
PE100
PEHD
11
mobile amorphous
Effect of Stabilization on the Thermal Aging of PA12 at 140 °C
High-Field NMR Relaxometry
FT-IR
Viscosimetry
DSC
NMR-MOUSE Relaxometry
Methods
Aging time [days]
Aging time [days]
Stabilized PA12
Non-stabilized PA12
12 J. Zhang and A. Adams, Polym. Degrad. Stab. 134, 169-178 (2016)
Depth-Dependent NMR Morphology
13
0 20 40 60 80 1000.00
0.04
0.08
0.12
Car
bony
l ind
ex [A
1718
/A11
93]
Aging time [days]
non-stabilized
stabilized
middle of the plates
0 20 40 60 80 10040
60
80
100
M [k
g/m
ol]
Aging time [days]
non-stabilized
stabilized
0 400 800 1200 16000.9
1.0
1.1
1.2
1.3
5 days 30 days 10 days 100 days 20 days
T 2eff_
long
[ms]
Distance away from the surface [µm]
stabilized
0 500 1000 1500 2000 2500
0.6
0.8
1.0
2 days 5 days 10 days 50 days
T 2eff_
long
[ms]
Distance away from the surface [µm]
non-stabilized
Supporting the NMR Results
FT-IR
Viscosimetry
J. Zhang and A. Adams, Polym. Degrad. Stab. 134, 169-178 (2016)
surface
Monitoring the UV-Aging of PA12
0 2000 4000 60004.0
4.2
4.4
4.6
4.8
5.0
UV Aging Time 0 h 1000 h 2000 h
T 2eff [
ms]
Depth [µm]
Stabilized PA12,
another stabilizer type UV-light
14
0 1000 2000 3000 40000.4
0.5
0.6
0.7
0.8
0.9
T 2e
ff [m
s]
Depth [µm]
UV Aging Time 0 h 500 h 2000 h
UV-light Non-Stabilized PA12
Decrease in m
obility
A. Adams, TrAc, 83, 107-119 (2016)
Polyethylene
Coating UV-light
R. Kwamen, B. Blümich, and A. Adams, Macromol. Rapid Com., 33(10), 943-947 (2012)
UV-Aging of Polyethylene Coatings by 1H Self-Diffusion Coefficients
UV exposed
UV non-exposed
H.-J. Kocks et al 3R Int. 2011 , 8/9 , 618. Elongation [%]
0 200 400 600 0
100
200
Forc
e [N
]
100
200
Forc
e [N
]
15
Monitoring the Ingress of Solvents in Polymers
Biodiesel in Polyethylene
BD BD Polyethylene
60 °C
0 1000 2000 30000.3
0.4
0.5
0.6
0.7
0.8
0.9
T 2ef
f_ lo
ng [m
s]Depth [µm]
0 days3 days
14 days56 days
112 days
Biodiesel in Polypropylene
Polypropylene
60 °C
BD BD
Increase in mobility
0 1000 2000 3000
2
4
6
8
10
T 2ef
f_ lo
ng [m
s]
Depth [µm]
0 days
3 days
14 days
56 days
112 days
Increase in mobility
16
Increase in mobility
Hydrolytic Aging of PA12
H2O H2O Polyamide 12
Supported by BMBF Project „KOWIND“
6000 µm
17
Chemical Aging of Crosslinked Polyethylene
Changes in the Weight
Mechanical Measurements
Crosslink Density Measurements
Differential Scanning Calorimetry (DSC)
NMR-MOUSE
Methods
18
Exposure to 6 various aging media at 60 °C up to 6 months
The changes in the relaxation time of the amorphous phase correlate with the changes of the tensile strength.
With the help of a calibration curve, the mechanical state of a pipe at a certain time can be predicted by simple nondestructive NMR measurements.
Correlation NMR/Mechanical Measurements
A. Adams, A. Piezeck, G. Schmitt, and G Siegmund, Anal. Chim. Acta, 887,163-171 (2015) 19
NMR methods working at high and low magnetic field were successfully applied to characterize:
Morphological changes of PE pipe grades during a hydrostatic pressure test Morphological changes during thermal and UV-aging of stabilized and non-
stabilized PA12 samples Ingress of solvents in various polymers Chemical aging of crosslinked PE
The mobility of the amorphous phase is the most sensitive microscopic parameter towards aging. Correlations of the single-sided NMR data with the mechanical measurements could enable in-situ mechanical condition monitoring.
Conclusions
20
Thank you to my Collaborators: Dr. N. Sun, former RWTH Aachen
Dr. R. Kwamen, former RWTH Aachen
J. Zhang, former RWTH Aachen
M. Adams, RWTH Aachen
Thank You very much for your attention!
Dr. J. Kocks, Siegen
Prof. Dr. G. Schmitt, FH Iserlohn
Dr. J. Berger, Evonik Marl
21
Questions? Then, please contact me at: [email protected]
![COVER SHEETPulsed field gradient (PFG) NMR is a highly versatile method for measuring molecular transport and diffusion [1], which is in large part due to the ability to tailor NMR](https://img.pdfslide.net/doc/110x75/5f0490937e708231d40e98b3/cover-sheet-pulsed-field-gradient-pfg-nmr-is-a-highly-versatile-method-for-measuring.jpg)
