Thermoplastic Polyurethane Elastollan Material Properties

2

Contents

Introduction

Chemical structurePhysical propertiesMechanical properties

Thermal properties

Gas permeability

Electrical properties

4

5

6

6

Rigidity 7

Shore hardness 9

Glass transition temperature 10

Torsion modulus 11

Tensile strength 14

Tear strength 21

Creep behaviour 22

Compression set 24

Impact strength 24

Abrasion 25

Friction 25

26

Thermal expansion 26

Thermal deformation 27

Vicat softening temperature 27

Heat deflection temperature 28

Thermal data 29

Maximum service temperature 30

31

33

Tracking 33

Dielectric strength 33

Surface resistivity 33

Volume resistivity 34

Dielectric constant 34

Dielectric loss factor 34

3

Contents

Chemical propertiesSwelling

Chemical resistance

Microbiological resistance

Hydrolysis resistance

Radiation resistance

Ozone resistance

Fire behaviour

Quality management

Index of key terms

35

35

36

Acids and alkaline solutions 36

Saturated hydrocarbons 36

Aromatic hydrocarbons 36

Lubricating oils and greases 37

Solvents 37

38

39

40

UV-radiation 40

High energy irradiation 40

40

41

42

43

4

Introduction

Elastollan is the registered trademark of our thermoplasticpolyurethane elastomers (TPU),which are available in unplasticizedform in a hardness range from60 Shore A to 74 Shore D.

These materials are distinguished bythe following properties:

● high wear and abrasionresistance

● high tensile strength andoutstanding resistance to tearpropagation

● excellent damping characteristics● very good low-temperature

flexibility● high resistance to oils, greases,

oxygen and ozone.

5

Chemical structure

Elastollan is essentially formed fromthe inter-reaction of three compo-nents:

1. polyols (long-chain diols)2. diisocyanates3. short-chain diols

The polyols and the short-chaindiols react with the diisocyanatesthrough polyaddition to form linearpolyurethane. Flexible segments arecreated by the reaction of the polyolwith the diisocyanate. The combina-tion of diisocyanate with short-chaindiol produces the rigid component(rigid segment). Fig. 1 shows in dia-grammatic form the chain structureof thermoplastic polyurethane.

The properties of the productdepend on the nature of the rawmaterials, the reaction conditions,and the ratio of the starting materials.The polyols used have a significantinfluence on certain properties of thethermoplastic polyurethane.

Either polyester-based polyols (B, C,S, 500 and 600 grades) or polyether-based polyols (1100 grades) areused in the production of Elastollan.

The products are distinguished bythe following characteristic features:

Polyester polyol:

● highest mechanical properties● highest heat resistance● highest resistance to mineral oils

Polyether polyol:

● highest hydrolysis resistance● best low-temperature flexibility● resistance to microbiological

degradation

In addition to the basic componentsdescribed above, many Elastollanformulations contain additives tofacilitate production and process-ability. Further additives can also beincluded to modify specific proper-ties.

Such additives include mould releaseagents, flame retardants, UV-stabi-lizers and plasticizers for flexiblegrades. Glass fibres are used toincrease rigidity (RTPU, Elastollan Rgrades).

Structure of thermoplastic Polyurethane

Fig. 1

Flexible segmentFlexible

segment Rigid segmentRigidsegment

= Residue of long-chain diol (ether/ester)

= Residue of short-chain diol

= Residue of diisocyanate

= Urethane group

6

Physical propertiesMechanical properties

The physical properties of Elastollanare discussed below. The testprocedures are explained in somedetail. Typical values of these testsare presented in our TechnicalInformation ”Elastollan – ProductRange“ and in separate data sheets.

Tests are carried out on injectionmoulded samples using granulatewhich is pre-dried prior to process-ing. Before testing specimens areconditioned for 20 hours at 100°Cand then stored for at least 24 hoursat 23 °C and 50% relative humidity.

The values thus obtained cannotalways be directly related to theproperties of finished parts. Thefollowing factors affect the physicalproperties to varying degrees:

● part design● processing conditions● orientation of macromolecules

and fillers● internal stresses● moisture● annealing

Consequently, finished parts shouldbe tested in relation to their intendedapplication.

7


The versatility of polyurethanechemistry makes it possible to pro-duce Elastollan over a wide range ofrigidity.

Fig. 2 shows the range of E-modulusof TPU and RTPU in comparison toother materials.

The modulus of elasticity (E-modulus) is determined bytensile testing according to DIN EN ISO 527-2 at a strain rate of1 mm/min, using a type A test speci-men according to DIN EN ISO 3167.The E-modulus is calculated fromthe initial slope of the stress-straincurve as ratio of stress to strain.

It is known that the modulus of elas-ticity of plastics is influenced by thefollowing parameters:

● temperature● moisture content● orientation of macromolecules

and fillers● rate and duration of stress● geometry of test specimens● type of test equipment

Figs. 3–5 show the modulus ofelasticity of several Elastollan gradesas a function of temperature.

E-modulus values obtained from thetensile test are preferable to thosefrom the bending test, since in thetensile test the stress distributionthroughout the relevant testspecimen length is constant.

Rigidity

Comparison of E-modulus of TPU and RTPU with other materials

Fig. 2

E-modulus [MPa]1 10 100 1000 10000 100000 1000000

TPU/RTPU

PVC

PE

Rubber

PC

PA

ABS

Al St

8


Rigidity

–20 –10 0 10 20 30 40 50 60 70 80

10 000

1000

100

10

Influence of temperature on E-modulusElastollan polyester types

Fig. 3

E-m

odul

us [M

Pa]

Temperature [°C]

C 64 D

C 95 A

C 85 A

–20 –10 0 10 20 30 40 50 60 70 80

10 000

1000

100

10

Influence of temperature on E-modulus Elastollan polyether types

Fig. 4

E-m

odul

us [M

Pa]

Temperature [°C]

1164 D

1195 A

1185 A

–20 –10 0 10 20 30 40 50 60 70 80 90 100

10 000

1000

100

Influence of temperature on E-modulusElastollan glassfibre reinforced types

Fig. 5

E-m

odul

us [M

Pa]

Temperature [°C]

R 3000

R 1000

R 2000

9


The hardness of elastomers such asElastollan is measured in Shore Aand Shore D according to DIN 53505 (ISO 868).

Shore hardness is a measure of theresistance of a material to the pene-tration of a needle under a definedspring force. It is determined as anumber from 0 to 100 on the scalesA or D. The higher the number, thehigher the hardness. The letter A isused for flexible types and the letterD for rigid types. However, theranges do overlap.

Fig. 6 shows a comparison of theShore hardness A and D scales forElastollan. There is no generaldependence between Shore A and Dscales. Under standard atmosphericconditions (i.e. 23 °C, 50% relativehumidity), the hardness of Elastollangrades ranges from 60 Shore A to74 Shore D.

Shore hardness reduces as tempera-ture rises. Fig. 7 shows the variationof Shore hardness with temperaturefor various Elastollan grades.

Shore hardness

0 10 20 30 40 50 60 70 80 90 100

100

90

80

70

60

50

40

30

20

Relationship: Shore A to Shore D

Fig. 6

Har

dnes

s S

hore

A

Hardness Shore D

–30 –10 10 30 50 70 90 110 130

100

90

80

70

60

50

40

30

20

10

0

Influence of temperature on hardnessElastollan polyester types

Fig. 7

Har

dnes

s [S

hore

D]

Temperature [°C]

C 64 DC 95 A

C 80 A

10


The glass transition temperature (Tg)of a plastics is the point at which areversible transition of amorphousphases from a hard brittle conditionto a visco-elastic or rubber-elasticcondition occurs. Glass transitiontakes place, depending on hardnessor rather amorphous portion of amaterial, within a more or less widetemperature range. The larger theamorphous portion (softer Elastollanproduct), the lower is the glasstransition temperature, and thenarrower is this temperature range.

There are several methods availableto determine glass transition temper-ature, each of them possibly yieldinga different value, depending on thetest conditions. Dynamic testingresults in higher temperature valuesthan static testing. Also the thermalhistory of the material to bemeasured is of importance. Thus,similar methods and conditions haveto be selected for comparison ofglass transition temperatures ofdifferent products.

Fig. 8 shows the glass transitiontemperatures of several Elastollantypes, measured by differentialscanning calorimetry (DSC) at aheating rate of 10 K/min. The Tg wasevaluated according to DIN 51007on the basis of the curve, the slopeof which is stepped in the transitionrange.

The torsion modulus and the damp-ing curves shown in figs. 9 to 14 enable Tg’s to be defined on thebasis of the damping maximum.Since this is a dynamic test, the Tg’sexceed those obtained from theDSC measurements.

Glass transition temperature

C 85 A C 95 A C 64 D 1185 A 1195 A 1164 D

–50

–40

–30

–20

–10

0

Glass transition temperature (Tg) from DSC at 10 K/min

Fig. 8

Tg [°

C]

Elastollan type

11


The torsion vibration test asspecified in DIN EN ISO 6721-2is used to determine the elasticbehaviour of polymeric materialsunder dynamic torsional loading,over a temperature range. In thistest, a test specimen is stimulatedinto free torsional vibration. Thetorsional angle is kept low enough toprevent permanent deformation.Under the test parameters specifiedin the standard, a frequency of 0.1 to10 Hz results as temperature in-creases.

During the relaxation phase thedecreasing sinusoidal vibration isrecorded. From this decay curve, itis possible to calculate the torsionmodulus and damping. The torsionmodulus is the ratio between thetorsion stress and the resultantelastic angular deformation.

Figs. 9–14 show the torsion modulusand damping behaviour over atemperature range for severalElastollan grades.

At low temperature torsion modulusis high and the curves are relativelyflat. This is the so-called energy-elastic temperature range, wheredamping values are low.

With rising temperature, the torsionmodulus curve falls and dampingbehaviour increases. This ist the so-called glass transition zone, wheredamping reaches a maximum.

After the glass transition zone, thetorsion modulus curve flattens. Thiscondition is described as entropy-elastic (rubber-elastic). At thistemperature the material remainssolid with increasing temperature,torsion modulus declines moresharply and damping increasesagain. Here, the behaviour pattern ispredominantly visco-elastic.

The extent of each zone variesaccording to Elastollan type.

However, as a general statement,the transition becomes more obviouswith the lower hardness Elastollangrades.

Torsion modulus

12


Torsion modulus

–50 –25 0 25 50 75 100 125 150

10 000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan C 85 A

Fig. 9

Tors

ion

mod

ulus

[MP

a]

Temperature [°C]

Torsion modulus

Damping

–50 –25 0 25 50 75 100 125 150

10 000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan C 64 D

Fig. 11

Tors

ion

mod

ulus

[MP

a]

Temperature [°C]

Dam

ping

[–]

–50 –25 0 25 50 75 100 125 150

10 000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan C 95 A

Fig. 10

Tors

ion

mod

ulus

[MP

a]

Temperature [°C]D

ampi

ng [–

]D

ampi

ng [–

]

Torsion modulus

Torsion modulus

Damping

Damping

13


Torsion modulus

–50 –25 0 25 50 75 100 125 150

10 000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan 1185 A

Fig. 12

Tors

ion

mod

ulus

[MP

a]

Temperature [°C]

Torsion modulus

Damping

Dam

ping

[–]

–50 –25 0 25 50 75 100 125 150

10 000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan 1195 A

Fig. 13

Tors

ion

mod

ulus

[MP

a]

Temperature [°C]

Torsion modulus

Damping Dam

ping

[–]

–50 –25 0 25 50 75 100 125 150

10 000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan 1164 D

Fig. 14

Tors

ion

mod

ulus

[MP

a]

Temperature [°C]

Torsion modulus

Damping

Dam

ping

[–]

Strength characteristics:

● The yield stress ÛÁ is the tensilestress at which the slope of thestress-strain curve becomeszero.

● Tensile strength Ûmax is the tensile stress at maximumforce.

● Tear strength ÛB is the tensilestress at the moment of rupture of the specimen.

Deformation characteristics:

● The yield strain ÂÁ is theelongation corresponding to theyield stress.

● Maximum force elongation Âmax is the elongation corres-ponding to the tensilestrength.

● Elongation at break ÂB is the elongation corresponding to the tear strength.


The behaviour of elastomers undershort-term, uniaxial, static tensilestress is determined by tensile testsas specified in DIN 53504 and maybe presented in the form of a stress-strain diagram. Throughout the test,the tensile stress is always related tothe original cross-section of the testspecimen. The actual stress, whichincreases steadily owing to theconstant reduction in cross-section,is not taken into account.

Typical strength and deformationcharacteristics can be seen in thetensile stress-strain diagramm(Fig. 15):

In the case of unreinforcedElastollan grades at room tempera-ture, differences are not generallyobserved, e.g., tear strength andtensile strength correspond (Fig. 16).

A yield stress is only observed withrigid formulations at lower tempera-tures.

For glass-fibre reinforced Elastollangrades (R grades), yield stress coin-cides with tensile strength (Fig. 17).

In one respect, the stress-straindiagrams on the following pages,determined according to DIN 53504present the typical high elongationto break. On the other hand theyinclude diagrams of lower deforma-tions. These diagrams and thecurves relating to the R-Types weredetermined according to DIN ENISO 527-2 at a rate of 50 mm/minusing a multipurpose test specimenaccording to DIN EN ISO 3167.

Tensile strength

14

15


Tensile strength

Typical stress-strain curve from tensile testing

Fig. 15

Str

ess Û

Strain Â

Ûmax

ÛB

Âmax =ÂB

ÛY

ÂY

Characteristic stress-strain curve for unreinforced Elastollan

Fig. 16

Str

ess Û

Strain Â

Ûmax =ÛB

Âmax =ÂB

Characteristic stress-strain curve for reinforced Elastollan

Fig. 17

Str

ess Û

Strain Â

ÛY = Ûmax

ÂY = Âmax ÂB

ÛB

16


Note:The graphs shown on pages 16 and17 were determined according toDIN 53504 at a rate of 200 mm/minusing test specimens of 2 mm thick-ness.

Tensile strength

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastollan C 85 A

Fig.18

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

100°C

60°C

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastollan C 95 A

Fig. 19

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

60°C

100°C

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastollan C 64 D

Fig. 20

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

60°C

100°C

17


Tensile strength

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastollan 1185 A

Fig. 21

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

100°C

60°C

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastollan 1195 A

Fig. 22

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

100°C

60°C

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastollan 1164 D

Fig. 23

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

100°C

60°C

0 5 10 15 20 25 30 35 40 45 50

8

6

4

2

0

18


Tensile strength

Elastollan C 85 A

Fig. 24

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

80°C

–20°C

23°C

40°C

0°C

0 5 10 15 20 25 30 35 40 45 50

25

20

15

10

5

0

Elastollan C 95 A

Fig. 25

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

0°C

80°C40°C

0 2 4 6 8 10 12 14 16 18 20

50

40

30

20

10

0

Elastollan C 64 D

Fig. 26

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

0°C

100°C

60°C

Note:The graphs on pages 18 and 19were determined according toDIN EN ISO 527-2 at a rate of50 mm/min using multipurpose testspecimens of 4 mm thicknessaccording to DIN EN ISO 3167.These curves present in more detailstress-strain performance over thetypical range of application.

19


Tensile strength

0 5 10 15 20 25 30 35 40 45 50

8

6

4

2

0

Elastollan 1185 A

Fig. 27

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

23°C

40°C

80°C

0°C

0 5 10 15 20 25 30 35 40 45 50

25

20

15

10

5

0

Elastollan 1195 A

Fig. 28

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

40°C

0°C

80°C

0 2 4 6 8 10 12 14 16 18 20

50

40

30

20

10

0

Elastollan 1164 D

Fig. 29

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

–20°C

23°C

0°C

–20°C

–20°C

23°C

60°C

100°C

20


Tensile strength

0 5 10 15 20 25 30 35 40

80

70

60

50

40

30

20

10

0

Elastollan R 1000

Fig. 30

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

40°C

23°C

0°C

60°C

0 5 10 15 20 25

100

80

60

40

20

0

Elastollan R 2000

Fig. 31

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

23°C

0°C

60°C

0 2 4 6 8 10 12 14 16 18 20

120

100

80

60

40

20

0

Elastollan R 3000

Fig. 32

Tens

ile s

tren

gth

[MP

a]

Elongation [%]

23°C

0°C

60°C40°C

Note:The graphs on page 20 were deter-mined according to DIN EN ISO 527-2at a rate of 50 mm/min usingmultipurpose test specimens of4 mm thickness according toDIN EN ISO 3167.

40°C

21


Tear strength

Tear strength is the term whichdefines the resistance of a notchedtest specimen to tear propagation.In this respect, Elastollan is farsuperior to most other of plastics.

The test is conducted in accordancewith DIN ISO 34–1Bb using anangle specimen with cut. Thespecimen is stretched at right-angles to the incision at a rate of 500 mm/min until tear. The tearresistance [kN/m] is the ratiobetween maximum force andspecimen thickness.

The diagrams show tear strength forseveral Elastollan grades, relative totemperature.

–40 –20 0 20 40 60 80 100 120

350

300

250

200

150

100

50

0

Tear strength in relation to temperatureElastollan polyester types

Fig. 33

Tear

str

engt

h [k

N/m

]

Temperature [°C]

C 80 AC 95 A

C 64 D

–40 –20 0 20 40 60 80 100 120

350

300

250

200

150

100

50

0

Tear strength in relation to temperatureElastollan polyether types

Fig. 34

Tear

str

engt

h [k

N/m

]

Temperature [°C]

1195 A

1180 A

1164 D

22


A pure elastic deformation behaviour,whereby the elastic characteristicremains constant, does not occurwith any material. Due to internalfriction, there exist at any time botha visco-elastic and a viscous defor-mation portion, causing a depen-dence of the characteristic values onthe stress duration and intensity.These non-elastic portions areconsiderably influenced by tempera-ture and time. This dependenceshould be a pre-consideration in thecase of plastics operating at ambienttemperature under long term load.

Behaviour under long-term staticstress can be characterized accord-ing to ISO 899 by means of creeptests, whereby a test specimen issubject to tensile stress using a load.The constant deformation thuscaused is measured as a function oftime. If this test is conductedapplying different loads, the datayield a so-called isochronousstress-strain diagram. Such a diagram can be used topredict how a component deforms inthe course of time under a certainload, and also how the stress in acomponent decreases with a givendeformation (Figs. 35 to 39).

Creep behaviour

1,5

1,0

0,5

00 2 4 6 8 10 12 14 16 18 20

1 h 10 h 100 h 1000 h 10000 h 100000 h

Isochronous stress-strain lines at 23°CElastollan C 85 A

Fig. 35

Str

ess

[M/P

a]

Strain [%]

8

7

6

5

4

3

2

1

00 1 2 3 4 5 6 7 8 9 10 11 12

1 h 10 h 100 h 1000 h 10000 h 100000 h

Isochronous stress-strain lines at 23°CElastollan C 64 D

Fig. 36

Str

ess

[M/P

a]

Strain [%]

23


Creep behaviour

1,5

1,0

0,5

00 2 4 6 8 10 12 14 16 18 20

1 h 10 h 100 h 1000 h 10000 h

100000 h

Isochronous stress-strain lines at 23°CElastollan 1185 A

Fig. 37

Str

ess

[M/P

a]

Strain [%]

5

4

3

2

1

00 1 2 3 4 5 6 7 8 9 10 11 12

1 h 10 h 100 h 1000 h

100000 h

10000 h

Isochronous stress-strain lines at 23°CElastollan 1164 D

Fig. 38

Str

ess

[M/P

a]

Strain [%]

1 h 10 h 100 h 1000 h 10000 h 100000 h35

30

25

20

15

10

5

00 1 2 3 4 5 6 7 8 9 10

Isochronous stress-strain lines at 23°CElastollan R 3000

Fig. 39

Str

ess

[M/P

a]

Strain [%]

24


Compression set [%] is determinedby a constant deformation test overa period of 24 hours and is standard-ized in DIN ISO 815.

In application, in the event ofcompressive stress one should notexceed 5% compression for themore rigid grades and 10% for themore flexible grades, if noticeablecompression set is to be avoided.

To achieve the best resistance tocompression set annealing of thefinished parts is recommended.

Compression set

Impact strength

Impact strength Notched impact strength

Elastollan C 85 A down to –60 °C fracture from –50°Cno fracture

Elastollan C 95 A down to –60 °C fracture from –40°Cno fracture

Elastollan C 60 D down to –60 °C fracture from –20°Cno fracture

Elastollan 1185 A down to –60 °C fracture from –60°Cno fracture

Elastollan 1195 A down to –60 °C fracture from –50°Cno fracture

Elastollan 1160 D down to –60 °C fracture from –30°Cno fracture

Table 1

Elastollan grades have outstandinglow-temperature impact strength.The tables below give a survey ofCharpy flexural impact tests accord-ing to DIN EN ISO 179.

Impact strength Notched impact strenght

23°C –30°C 23°C –30°C

Elastollan R 1000 no fracture 130 70 20

Elastollan R 2000 140 110 50 10

Elastollan R 3000 120 70 30 10

Values in kJ/m2

Table 2

25


Abrasion [mm3] is determined inaccordance with DIN 53516(ISO 4649). A test specimen isguided at a defined contact pressureon a rotating cylinder covered withabrasive test paper. The totalfrictional path is approx. 40 m. Themass loss due to abrasion wear ismeasured, taking into account thedensity of the material and the sharp-ness of the test paper. The abrasionis given as the loss of volume in mm3.Elastollan shows very low abrasion.

Under practical conditions, TPU isconsidered to be the most abrasionresistant elastomeric material.Thorough predrying of the granulateprior to processing is howeveressential to achieve optimumabrasion performance.

Abrasion

Any meaningful evaluation of thefrictional behaviour of plastics isdifficult since frictional processes inpractice have side-effects which aredifficult to define.

The frictional behaviour of Elastollanproducts depends upon hardness.Friction increases with reducinghardness and this can lead to „stick-slip“ effects for softer products.

Friction

26

Physical propertiesThermal properties

As all materials, Elastollan is subjectto a temperature-dependent,reversible variation in length. This isdefined by the coefficient of linearexpansion · [1/K] in relation totemperature and determined inaccordance with DIN 53752.

Fig. 40 compares the coefficients oflinear expansion of some Elastollantypes with steel and aluminium andillustrates the dependence ontemperature and Shore hardness.

As shown the values for reinforcedElastollan (glass fibre content 20%)are similar to those for steel andaluminium.

The influence of temperature isobvious and has to be consideredfor many applications!

Thermal expansion

200

180

160

140

120

100

80

60

40

20

0–40 –20 0 20 40 60 80

Coefficient of thermal expansion · [1/K]Various Elastollan hardnesses

Fig. 40

·(t

) [10

E–6

·1/

K]

Temperature [°C]

Shore 80 A

Shore 95 A

Shore 64 D

AluminiumSteelRTPU

27


Various tests can be used tocompare the application limits ofplastics at increased temperature.These include the determination ofthe Vicat Softening Temperature(VST) according to ISO 306 and the determination of the HeatDeflection Temperature (HDT)according to ISO 75.

In the course of this test, a loadedneedle (Vicat A: 10 N, Vicat B: 50 N)with a diameter of 1 mm2 is placedon a test specimen, which is locatedon a plane surface within a tempera-ture transfer medium. The tempera-ture of the medium (oil or air) isincreased at a constant heating rate(50 K/h or 120 K/h). The VST is thetemperature at which the needlepenetrates by 1 mm into the testmaterial.

Thermal deformation

Vicat softening temperature

140

120

100

80

60

40

20

0C 64 D R 1000 R 2000 R 30001164 D

Vicat temperature (VST) according to DIN EN ISO 306, method B 50

Fig. 41

VS

T [°

C]

Elastollan type

28


Similarly to the Vicat test, the testset-up is heated in a heat transfermedium at a rate of 50 or 120 K/h.The arrangement ist designed as3-point bending test, the test piecebeing stressed at a constant loadwhich corresponds to a bendingstress of 0.45 MPa, 1.80 MPa or 8 MPa (method A, B or C), depend-ing on the rigidity of the material.The temperature at which the testpiece bends by 0.2 to 0.3 mm(depending on the height of the testpiece) is indicated as HDT.

Heat deflection temperature

180

160

140

120

100

80

60

40

20

0C 64 D R 1000 R 2000 R 30001164 D

Heat deflection temperature (HDT) according to DIN EN ISO 75,method B

Fig. 42

HD

T [°

C]

Elastollan type

29


Thermal data

Representative values of thermal data of Elastollan

Properties according to Unit Valuessoftkhard

Thermal conductivity DIN 52612 W/m K 0,19k0,25

Heat of combustion DIN 51900– heating value J/g 25000k29000– burning value J/g 26000k31000

Specific heat DIN 51005– room temperature J/g K 1,5k1,8– melt temperature J/g K 1,7k2,3

Table 3

30


The life expectancy of a finishedTPU part will be influenced byseveral factors and is difficult topredict exactly.

The ageing behaviour of materialscan however be compared by useof the so-called ARRHENIUStechnique. Measurements conduct-ed at higher temperatures can beextrapolated to predict performanceat lower temperatures.

In the diagram below, the endcriterion is taken as time for tensilestrength to be reduced to 20 N/mm2.

Maximum service temperature

100000

10000

1000

100

1080 90 100 110 120 130 140 150 160

Elastollan 1185 A

Elastollan C 85 A

Longterm air ageing

Fig. 43

Exp

osur

e tim

e [h

]

Temperature [°C]

End criterion: tensile strength 20 MPa

31

Physical propertiesGas permeability

The passage of gas through a testspecimen is called diffusion. Thistakes place in three stages:

1. Solution of the gas in the testspecimen.

2. Diffusion of the dissolved gasthrough the test specimen.

3. Evaporation of the gas from thetest specimen.

The diffusion coefficient Q [m2/(s · Pa)] is a material con-stant which specifies the volume ofgas which will pass through a testspecimen of known surface areaand thickness in a fixed time, with agiven partial pressure difference.The coefficient varies with tempera-ture and is determined in accor-dance with DIN 53536.

Table 4 shows the gas diffusioncoefficients of Elastollan grades forvarious gases at a temperature of20 °C.

The variation of diffusion coefficientwith temperature using Elastollan1185 A and nitrogen as example isillustrated in Fig. 44.

The water vapour permeabilityWDD [g/(m2 · d)] of a plastic isdetermined in accordance withDIN 53122 part 1. This is defined asthe amount of water vapour passingthrough 1 m2 of test specimen underset conditions (temperature, humi-dity differential) in 24 hours, and isroughly in inverse proportion tospecimen thickness.

The figures shown in Table 5 wereobtained with a temperature of 23 °Cand a humidity differential of 93%relative humidity. All values relate toa thickness of 1 mm.

Gas permeability coefficient Q [m2/(s · Pa)] · 10–18

Elastollan-Gas

type Ar CH4 CO2 H2 He N2 O2

C 80 A 12 11 200 45 35 4 14

C 85 A 9 6 150 40 30 3 10

C 90 A 5 4 40 30 25 2 7

C 95 A 3 2 20 20 20 1 4

1180 A 14 18 230 70 50 6 21

1185 A 9 14 180 60 40 5 16

1190 A 7 9 130 50 30 4 12

1195 A 6 5 90 40 20 3 8

Table 4

32

Physical propertiesGas permeability

120

100

80

60

40

20

00 20 40 60 80 100 120

Affect of temperature on permeability coefficient:Elastollan 1185 A with Nitrogen

Fig. 44

Per

mea

blity

coe

ffici

ent Q

[m2

/(s ·

Pa)

] 10-1

8

Temperature [°C]

Water vapour permeability WDD [g/(m2 · d)]measured at 1 mm section

Elastollan type WDD Elastollan type WDD

C 80 A 18 1180 A 21

C 85 A 15 1185 A 17

C 90 A 20 1190 A 15

C 95 A 8 1195 A 12

Table 5

33

Physical propertiesElectrical properties

The electrical conductivity ofplastics is very low. They are, there-fore, frequently used as insulatingmaterials. Information on relevantproperties for electrical applicationsmust therefore be made available.

For Elastollan grades standardresistance measurements are madeon conditioned test specimens (20 h, 100°C) after storage in thestandard conditioning atmosphere,i.e. 23 °C, 50% relative humidity.

Allowance should be made for thefact that electrical properties aredependent on moisture content,temperature and frequency.

The results are presented in ourtechnical information brochure”Elastollan – ElectricalProperties“.

Tracking results from the progres-sive formation of conductive pathson the surface of a solid insulatingmaterial. It is generated by theaction of electrical loading andelectrolytic impurities on the surface.

The Comparative Tracking Index(CTI) determined in accordancewith IEC 60112 is the maximumvoltage at which a material will with-stand 50 drops of a defined testsolution without tracking.

General

Tracking

Dielectric strength according to IEC 60243 is the ratio betweendisruptive voltage and the distanceof the electrodes separated by theinsulating material. Disruptive volt-age is the a.c. voltage at which pointthe insulating material breaks down.

Dielectric strength

The specific surface resistance isthe resistance of the surface of atest piece. It is measured betweentwo electrodes of dimensions pre-scribed in IEC 60093, fixed to thesurface at a specified distance.

Surface resistivity

34

Physical propertiesElectrical properties

Volume resistivity as defined in IEC 60093 is the electrical resis-tance of the bulk material measuredbetween two electrodes, relative tothe geometry of the test piece. Thetype of electrode arrangementmakes it possible to ignore surfaceresistance.

Dielectric constant is the ratio ofcapacity measured with the insulat-ing material compared with that forair. This constant is determined inaccordance with IEC 60250 and istemperature and frequency depen-dent. Our technical informationprovides values for Elastollan gradesfor various frequencies at 23 °C.

Volume resistivity

Dielectric constant

When an insulating material is usedas dielectric in a capacitor, an ad-justment of the phase displacementbetween current and voltage occurs.The displacement from the normalangle of 90 ° is known as the lossangle. The loss factor is defined asthe tangent of the loss angle. As withdielectric constant, it varies withtemperature and frequency. Valuesare provided for various frequenciesat 23 °C.

Dielectric loss factor

35

Chemical propertiesSwelling

The suitability of a plastic for aparticular application often dependson its resistance to chemicals.Depending on the type and chemicalcomposition thermoplasticpolyurethanes can behave verydifferently in interreaction withchemical substances.

It is therefore difficult in any case tomake a clear distinction between theeffects described below.

Our data sheet ”Elastollan –Chemical resistance“ provides ageneral guide. For critical applica-tions, a detailed resistance testconsidering both swelling and theaffect on mechanical properties isrecommended.

Swelling is the fundamental physicalprocess of the absorption of liquidsubstances by a solid.

In this process, the substanceenters into the material withoutchemical interaction. This results inan increase in volume and weightwith a corresponding reduction inmechanical values.

After evaporation a reduction inswelling occurs and the originalproperties of the product are almostcompletely restored.

Swelling is a reversible process.

General

Swelling

36

Chemical propertiesChemical resistance

Chemical resistance depends on theperiod of exposure, the temperature,the quantity, the concentration andthe type of the chemical substance.

In the case of chemical degradationof polyurethane the chemical reac-tion results in cleavage of the molec-ular chains. This process is generallypreceded by swelling. In the courseof degradation, polyurethane losesstrength, and in extreme cases thiscan lead to disintegration of thepart.

Elastollan products are attacked byconcentrated acids and alkalinesolutions even at room temperature.Any contact with these substancesshould be avoided. Elastollan isresistant to short-time contact withdilute acids and alkali solutions atroom temperature.

Acids and alkaline solutions

Contact of Elastollan with saturatedhydrocarbons such as diesel oil,isooctane, petroleum ether andkerosene, results in a limitedswelling. At room temperature thisswelling amounts to approx. 1–3 %and the resultant reduction in tensilestrength is no more than 20 %. Afterevaporation and reversal of theswelling, the original mechanicalproperties are almost completelyrestored.

Saturated hydrocarbons

Contact of Elastollan with aromatichydrocarbons such as benzene andtoluene, results in considerableswelling even at room temperature.Absorption can result in a 50%weight increase with a correspond-ing reduction in mechanical proper-ties.

Aromatic hydrocarbons

37

Chemical propertiesChemical resistance

Elastollan is in principal resistant tolubricating oils and greases, how-ever irreversible damage can becaused by included additives.

Compatibility testing in eachindividual lubricant is to berecommended.

No reduction in strength occurs afterimmersion in ASTM oils 1, IRM 902and IRM 903 at room temperature.No reduction in tensile strength isrecorded after 3 weeks immersion at100°C.

Lubricating oils and greases

Aliphatic alcohols, such as ethanoland isopropanol, cause swelling ofElastollan products. This is com-bined with a loss of tensile strength.Rising temperatures intensify theseeffects.

Ketones such as acetone, methyl-ethylketone (MEK) and cyclo-hexanone are partial solvents forthermoplastic polyurethane elasto-mers. Elastollan products areunsuitable for long-term use in thesesolvents.

Aliphatic esters, such as ethylacetate and butyl acetate, causesevere swelling of Elastollan.

Highly polar organic solvents suchas dimethylformamide (DMF),dimethylsulphoxide (DMSO),N-methylpyrrolidine and tetrahydro-furan (THF) dissolve thermoplasticpolyurethane.

Solvents

38

Chemical propertiesMicrobiological resistance

When using polyester-basedthermoplastic polyurethane underclimatic conditions of high heat andhumidity, parts can be damaged bymicrobiological attack. In particular,micro-organisms producingenzymes are able to affect themolecule chains of polyester-basedTPU. The microbiological attackinitially becomes visible asdiscolouration. Subsequently,surface cracks occur which enablethe microbes to penetrate deeperand to cause a complete destructionof the TPU (ref. Fig. 45).

Polyether-based thermoplasticpolyurethane is resistant to micro-biological attack.

The saponifiction number (SN)according to DIN VDE 0472, part704 is an important criterion formicrobiological resistance. UnfilledTPU is resistant to microbes up to asaponification number of 200 mgKOH/gm, which is the limiting valueaccording to VDE 0282/10.

Depending on formulation and hard-ness, polyether-based TPUs achievea saponification number of around150, polyester-based TPUs around450. With regard to polyether-poly-ester mixtures, the saponificationnumber can be calculated from the quantitative portions. Smallinclusions of up to approx. 10% ofester urethane in ether urethane(e.g. addition of ester-based colourmasterbatches) do not impair themicrobiological resistance (SNremains < 200). Larger inclusionsof ester-based TPU result in areduction in the microbiologicalresistance.

Progress of microbial degradation of polyester-based TPU

Fig. 45

Left: reference sample Middle: mild discolourationRight: discolouration and distinctly visible cracks

39

Chemical propertiesHydrolysis resistance

If polyester based polyurethanes areexposed for lengthy periods to hotwater, moisture vapour or tropicalclimates, an irreversible break-downof the polyester chains occursthrough hydrolysis. This results in areduction in mechanical properties.This effect is more marked in flexiblegrades, where the polyester contentis correspondingly higher than in theharder formulations. Degradation ofpolyester-based Elastollan is how-ever rarely experienced at roomtemperature.

Because of its chemical structure,polyether-based Elastollan is muchmore resistant to hydrolyticdegradation.

The following diagrams comparehydrolysis resistance of polyether-and polyester-based TPU.

100000

10000

1000

100

1050 60 70 80 90 100

Elastollan 1185 A

Elastollan C 85 A

Long term hydrolysis resistance

Fig. 46

Imm

ersi

on ti

me

[h]

Temperature [°C]

End criterion: tensile strength 20 MPa

100000

10000

1000

100

1050 60 70 80 90 100

Elastollan 1185 A

Elastollan C 85 A

Long term hydrolysis resistance

Fig. 47

Imm

ersi

on ti

me

[h]

Temperature [°C]

End criterion: elongation 300%

40

Chemical propertiesRadiation resistance · Ozone resistance

Plastics are chemically degraded by the effect of UV-radiation. Thedegree of ageing depends on dura-tion and intensity. In the case ofpolyurethanes, the effect is seeninitially as surface embrittlement.This is accompanied by a yellowingin colour and a reduction in mechan-ical properties.

It is possible to improve UV resis-tance by addition of colour pigmentswhich prevent the deep penetrationof UV-rays and thus mechanicaldestruction. Moreover, dark colourshades, in particular black, mask thesurface discolouration. The ageingprocess can also be delayed by theaddition of UV-stabilizers. Suitablemasterbatches are available.

UV-radiation

Elastollan is superior to most otherplastics in its resistance to high en-ergy radiation. Resistance to ·-, ‚-and Á-radiation is dependent onsuch factors as the intensity of theradiation, the shape and dimensionsof the test specimen, and theatmosphere in the test area.

The addition of crosslinking agentsand subsequent ‚- or Á-radiationcan effect crosslinking of Elastollan.The maximum achievable degrees ofcrosslinking are around 90%. This isa method to improve short-termheat deflection temperature andchemical resistance.

High energy radiation

The ozone molecule (O3) is formed bythe union of three oxygen atoms. It isgenerated from reaction of oxygen inthe atmosphere under the influenceof high energy UV-radiation.

Ozone is highly reactive, especiallywith organic substances. Rubber-based elastomers are destroyedthrough cracking under the influenceof ozone.

Elastollan, on the other hand, isresitant to ozone.

The test according to VDE 0472 part805 results in „crack-free“, stage 0.There is neither a loss of elasticity noran increase of surface hardness.

Ozone resistance

41

Chemical propertiesFire behaviour

Plastics are, like all organic sub-stances, inflammable. Fire behaviouris influenced by the followingcharacteristics:

● flammability● flame propagation● heat development● smoke development (smoke

density and toxicity of thecombustion gases)

● surface/mass ratio of thecombustible substances

● thermal-conductivity● calorific value

The fire behaviour of a substance isnot dependent on the material alone.Apart from the criteria listed above,is is also influenced by accompany-ing circumstances, such as:

● dispersion● nature of storage● quantity of material● temperature● ventilation● duration and intensity of the

source of ignition etc.

The complexity of the influencingfactors makes it impossible to give acomprehensive and generally-validdescription of the fire behaviour ofplastics. Consequently, there are anumber of standards and specifica-tions, each simulating a representa-tive case.

For the above reasons, in case ofuncertainty it is recommended toconsult our Technical ServiceDepartment. For certain applica-tions, it is advisable to use flamere-tardant Elastollan grades. Theseproducts provide increased protec-tion against flame development andpropagation.

No individual standard can coverevery eventuality. The mostimportant standards covering thebehaviour of platics in fire withtypical results for Elastollan aredesribed below:

● UL 94(Underwriters Laboratories)

Standard Elastollan grades arerated HB, grades containingplasticizer normally achieveclassification V2. The flameretardant halogen free gradeElastollan 1185 A FHF is rated V0.

Yellow Cards for some grades areavailable on request.

● ISO 4589 (Oxygen Index)

This test measures the minimumamount of oxygen required tomaintain combustion. ForElastollan grades values between22 and 25 are recorded.

● FMVSS 302 (Federal MotorVehicle Safety Standard)

All Elastollan grades comply withthis standard, which permits amax. combustion rate of 4 inches/min. (101.6 mm/min) under thespecified test conditions.

● DIN EN 50267-2-2(Corrosiveness of combustiongases)

Standard Elastollan grades as wellas grades containing plasticizerfullfil the requirements of this test.

Additives can influence the resultand must be considered separately.

Further details are to be found in oursafety data sheets.

42

Lagerung

Quality management

43

Index of key terms

43

A

Abrasion 25

Acid and alkali solutions 36

Ageing 40

Air ageing 30

Annealing 6, 24

B

Bending test 7

C

Chemical resistance 36

Chemical structure 5

Coefficientof linear expansion 26

Cold flexibility 20

Compression set 24

Compressive stress 24

Corrosivenessof cumbustion gas 41

CTI, ComparativeTracking Index 33

D

Damping 11

Deformation characteristics 14

Dielectric constant 34

Dielectric loss factor 34

Dielectric strength 33

Diffusion coefficient 31

Disruptive voltage 33

E

Electrical properties 33

Elongation 14

Elongation at break 14

Embrittlement 40

E-modulus 7

F

Fire behaviour 41

Flexural impact test 24

FMVSS 302 41

Friction 25

G

Gas permeability 31

Glass transition temperature 10

Glass transition zone 10

H

Hardness 9

Heat deflection temperature 28

Heat deformation behaviour 27

High energy irradiation 40

Hydrocarbon,aromatic 36saturated 36

Hydrolysis resistance 39

I

Impact strength 24

Isochronousstress-strain curves 22

L

Linear expansion 22

Long-term performance 22

Lubricating oils and greases 37

M

Maximum force elongation 14

Maximum service temperature 30

Mechanical properties 6

Microbiological resistance 38

Modulus of elasticity 7

N

Notched impact strength 24

O

Oxygen index 41

Ozone resistance 40

P

Physical properties 6

Q

Quality management 42

R

Radiation resistance 40

Rigidity 7

S

Saponification number 38

Service temperature 22

Shore hardness 9

Solvents 30

Specific heat 29

Stick-slip effect 25

Strength characteristics 14

Stress-strain curves 15

Surface resistance, specific 35

Swelling 35

T

Tear strength 21

Tensile strength 14

Thermal conductivity 29

Thermal data 29

Thermal expansion 26

Thermal properties 29

Torsion modulus 11

Torsion vibration test 11

Tracking 33

U

Underwriters Laboratories 41

UV-radiation 40

V

Vicat softening temperature 27

Volume resistivity 33

W

Water vapour permeability 32

Y

Yield strain 14

Yield stress 14

Documents

Thermoplastic Polyurethane Elastollan Material Properties