Elastollan Material PropertiesR1

8/11/2019 Elastollan Material PropertiesR1

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Contents

Introduction

Chemical structure

Physicalproperties

Mechanical 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


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Contents

Chemical properties

Swelling

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


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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 tear

propagation excellent damping characteristics

very good low-temperatureflexibility

high resistance to oils, greases,oxygen and ozone.


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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 hours

at 23C 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 macromoleculesand fillers

internal stresses

moisture

annealing

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


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The versati lity 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 toDIN 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 macromoleculesand fillers

rate and duration of stress

geometry of test specimens

type of test equipment

Figs. 35 show the modulus ofelasticity of several Elastollan grades

as 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 RTPUwith other materials

Fig. 2

E-modulus [MPa]

1 10 100 1000 10000 100000 1000000

TPU/RTPU

PVC

PE

Rubber

PC

PA

ABS

Al St


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Rigidity

20 10 0 10 20 30 40 50 60 70 80

10000

1000

100

10

Influence of temperature on E-modulusElastollan polyester types

Fig. 3

E-mo

du

lus

[MPa

]

Temperature [C]

C 64 D

C 95 A

C 85 A

20 10 0 10 20 30 40 50 60 70 80

10000

1000

100

10

Influence of temperature on E-modulusElastollan polyether types

Fig. 4

E-mo

du

lus

[MP

a]

Temperature [C]

1164 D

1195 A

1185 A

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

10000

1000

100

Influence of temperature on E-modulusElastollan glassfibre reinforced types

Fig. 5

E-mo

du

lus

[MPa

]

Temperature [C]

R 3000

R 1000

R 2000


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The hardness of elastomers such asElastollan is measured in Shore Aand Shore D according toDIN 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 to100 on the scales

A or D. The higher the number, thehigher the hardness. The letter A isused for flexible types and the letterD for rigid types. However, the

ranges 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

Hardness

Shore

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

Hardness

[Shore

D]

Temperature [C]

C 64 DC 95 A

C 80 A


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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 to14 enable Tgs to be defined on thebasis of the damping maximum.

Since this is a dynamic test, the Tgsexceed 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


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The torsion vibrat ion 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. 914 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


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Torsion modulus

50 25 0 25 50 75 100 125 150

10000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan C 85 A

Fig. 9

Tors

ionmo

du

lus

[MPa

]

Temperature [C]

Torsion modulus

Damping

50 25 0 25 50 75 100 125 150

10000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan C 64 D

Fig. 11

Tors

ionmo

du

lus

[MPa

]

Temperature [C]

Damp

ing

[]

50 25 0 25 50 75 100 125 150

10000

1000

100

10

1

100

10

1

0,1

0,01

Elastollan C 95 A

Fig. 10

Tors

ionmo

du

lus

[MPa

]

Temperature [C]

Damp

ing[

]

Damp

ing

[]

Torsion modulus

Torsion modulus

Damping

Damping


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Torsion modulus

50 25 0 25 50 75 100 125 150

10000

1000

100

10

1

100

10

1

0,1

0,01

Elastol lan 1185 A

Fig. 12

Tors

ionmo

du

lus

[MPa

]

Temperature [C]

Torsion modulus

Damping

Damp

ing

[]

50 25 0 25 50 75 100 125 150

10000

1000

100

10

1

100

10

1

0,1

0,01

Elastol lan 1195 A

Fig. 13

Tors

ionmo

du

lus

[MPa

]

Temperature [C]

Torsion modulus

Damping Damp

ing[

]

50 25 0 25 50 75 100 125 150

10000

1000

100

10

1

100

10

1

0,1

0,01

Elastol lan 1164 D

Fig. 14

Tors

ionmo

du

lus

[MPa

]

Temperature [C]

Torsion modulus

DampingDamp

ing

[]


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Strength characteristics:

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

Tensi le strength max is thetensile stress at maximumforce.

Tear strength B is the tensilestress at the moment ofrupture of the specimen.

Deformation characteristics:

The yield strain is theelongation corresponding to theyield stress.

Maximum force elongationmax is the elongation corres-ponding to the tensilestrength.

Elongation at break B is theelongation corresponding tothe 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 deformation

characteristics 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 st ress 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/min

using a multipurpose test specimenaccording to DIN EN ISO 3167.

Tensile strength

14


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Tensile strength

Typical stress-strain curve from tensile testing

Fig. 15

Stress

Strain

max

B

max =B

Y

Y

Characteristic stress-strain curve for unreinforced Elastollan

Fig. 16

Stress

Strain

max =B

max =B

Characteristic stress-strain curve for reinforced Elastollan

Fig. 17

Stress

Strain

Y = max

Y= max B

B


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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

iles

treng

th[MPa

]

Elongation [%]

20C

23C

100C

60C

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

iles

trength

[MPa

]

Elongation [%]

20C

23C

60C

100C

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

iles

treng

th[MPa

]

Elongation [%]

20C

23C

60C

100C


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Tensile strength

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastol lan 1185 A

Fig. 21

Tens

iles

treng

th[MPa

]

Elongation [%]

20C

23C

100C

60C

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastol lan 1195 A

Fig. 22

Tens

iles

trength

[MPa

]

Elongation [%]

20C

23C

100C

60C

0 100 200 300 400 500 600 700 800 900 1000

80

70

60

50

40

30

20

10

0

Elastol lan 1164 D

Fig. 23

Tens

iles

treng

th[MPa

]

Elongation [%]

20C

23C

100C

60C


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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

iles

treng

th[MPa

]

Elongation [%]

80C

20C

23C

40C

0C

0 5 10 15 20 25 30 35 40 45 50

25

20

15

10

5

0

Elastollan C 95 A

Fig. 25

Tens

iles

trengt

h[MPa

]

Elongation [%]

20C

23C

0C

80C

40C

0 2 4 6 8 10 12 14 16 18 20

50

40

30

20

10

0

Elastollan C 64 D

Fig. 26

Tens

iles

treng

th[MPa

]

Elongation [%]

20C

23C

0C

100C

60C

Note:The graphs on pages 18 and 19were determined according toDIN EN ISO 527-2 at a rate of50 mm/min using multipurpose test

specimens of 4 mm thicknessaccording to DIN EN ISO 3167.

These curves present in more detai lstress-strain performance over thetypical range of application.


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Tensile strength

0 5 10 15 20 25 30 35 40 45 50

8

6

4

2

0

Elastol lan 1185 A

Fig. 27

Tens

iles

treng

th[MPa

]

Elongation [%]

23C

40C

80C

0C

0 5 10 15 20 25 30 35 40 45 50

25

20

15

10

5

0

Elastol lan 1195 A

Fig. 28

Tens

iles

trength

[MPa

]

Elongation [%]

40C

0C

80C

0 2 4 6 8 10 12 14 16 18 20

50

40

30

20

10

0

Elastol lan 1164 D

Fig. 29

Tens

iles

treng

th[MPa

]

Elongation [%]

20C

23C

0C

20C

20C

23C

60C

100C


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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

iles

treng

th[MPa

]

Elongation [%]

40C

23C

0C

60C

0 5 10 15 20 25

100

80

60

40

20

0

Elastollan R 2000

Fig. 31

Tens

iles

trengt

h[MPa

]

Elongation [%]

23C

0C

60C

0 2 4 6 8 10 12 14 16 18 20

120

100

80

60

40

20

0

Elastollan R 3000

Fig. 32

Tens

iles

treng

th[MPa

]

Elongation [%]

23C

0C

60C

40C

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.

40C


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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 341Bb using anangle specimen with cut. Thespecimen is stretched at right-angles to the incision at a rate of500 mm/min unti l tear. The tearresistance [kN/m] is the ratiobetween maximum force and

specimen 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

Tears

treng

th[kN/m]

Temperature [C]

C 80 A

C 95 AC 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

Tears

treng

th[kN/m]

Temperature [C]

1195 A

1180 A

1164 D


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A pure elast ic 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 intensi ty.

These non-elast ic portions areconsiderably influenced by tempera-ture and time. This dependenceshould be a pre-consideration in thecase of plastics operating at ambient

temperature 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 certain

load, 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 23CElastollan C 85 A

Fig. 35

Stres

s[M/Pa

]

Strain [%]

8

7

6

5

4

3

2

1

0

0 1 2 3 4 5 6 7 8 9 10 11 12

1 h 10 h 100 h 1000 h 10000 h 100 000 h

Isochronous stress-strain lines at 23CElastollan C 64 D

Fig. 36

Stress

[M/Pa

]

Strain [%]


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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 23CElastollan 1185 A

Fig. 37

Stress

[M/Pa

]

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 23CElastollan 1164 D

Fig. 38

Stress

[M/Pa

]

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 23CElastollan R 3000

Fig. 39

Stress

[M/Pa

]

Strain [%]


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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 C

no 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


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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 evaluat ion 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


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26

Physical propertiesThermal properties

As all materia ls, Elastol lan 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 inf luence of temperature isobvious and has to be consideredfor many applications!

Thermal expansion

200

180

160

140

120

100

80

60

40

20

040 20 0 20 40 60 80

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

Fig. 40

(t)[10E

6

1/K]

Temperature [C]

Shore 80 A

Shore 95 A

Shore 64 D

AluminiumSteelRTPU


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Various tests can be used tocompare the application limits ofplastics at increased temperature.

These include the determinat ion oftheVicat Softening Temperature(VST) according to ISO 306 andthe 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

VST[C]

Elastollan type


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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 MPa, MPa or8 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

0

C 64 D R 1000 R 2000 R 30001164 D

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

Fig. 42

HDT[

C]

Elastollan type

1.80 0.45


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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


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

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

Exposure

time

[h]

Temperature [C]

End criterion: tensile strength 20 MPa


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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 coeffic ientQ [m2/(s Pa)] is a material con-stant which specifies the volume of

gas which will pass through a testspecimen of known surface areaand thickness in a fixed time, with agiven partial pressure difference.

The coeffic ient var ies with tempera-ture and is determined in accor-dance with DIN 53536.

Table 4 shows the gas di ffusioncoefficients of Elastollan grades forvarious gases at a temperature of20C.

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

The water vapour permeabi lityWDD [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 to

specimen thickness.

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

Gas permeability coefficient Q [m2/(s Pa)] 1018

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


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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

Permea

blitycoe

fficient

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


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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, 100C) after storage in thestandard conditioning atmosphere,i.e. 23C, 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 brochureElastollan 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 toIEC 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 a

test piece. It is measured betweentwo electrodes of dimensions pre-scribed in IEC 60093, fixed to thesurface at a specified distance.

Surface resistivity


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34

Physical propertiesElectrical properties

Volume resistiv ity as defined inIEC 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 of

capacity 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 used

as 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 23C.

Dielectric loss factor


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35

Chemical propertiesSwelling

The sui tabi lity 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 evaporat ion a reduction inswelling occurs and the originalproperties of the product are almostcompletely restored.

Swelling is a reversible process.

General

Swelling


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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 solut ions

Contact of Elastollan with saturatedhydrocarbons such as diesel oil,isooctane, petroleum ether andkerosene, results in a limitedswelling. At room temperature thisswelling amounts to approx. 13%and the resultant reduction in tensilestrength is no more than 20%. Afterevaporation and reversal of theswelling, the original mechanicalproperties are almost completely

restored.

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


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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 oils1, IRM 902and IRM 903 at room temperature.No reduction in tensile strength isrecorded after 3 weeks immersion at

100C.

Lubricating oils and greases

Aliphat ic 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.

Aliphat ic 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


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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-based

TPU. The microbiological attackinitially becomes visible asdiscolouration. Subsequently,surface cracks occur which enablethe microbes to penetrate deeperand to cause a complete destruction

of the TPU (ref. Fig. 45).

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

The saponif iction number (SN)according to DIN VDE 0472, part704 is an important criterion formicrobiological resistance. Unfilled

TPU 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 fromthe 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 inclusions

of ester-based TPU result in areduction in the microbiologicalresistance.

Progress of microbial degradation of polyester-based TPU

Fig. 45

Left: reference sampleMiddle: mild discolourationRight: discolouration and distinctly visible cracks


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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 fol lowing 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

Immers

iont

ime

[h]

Temperature [C]

End criterion: tensile strength 20 MPa

100000

10000

1000

100

10

50 60 70 80 90 100

Elastollan 1185 A

Elastollan C 85 A

Long term hydrolysis resistance

Fig. 47

Immers

ion

time

[h]

Temperature [C]

End criterion: elongation 300%


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Chemical propertiesFire behaviour

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

flammability

flame propagation

heat development

smoke development (smokedensity and toxicity of thecombustion gases)

surface/mass ratio of thecombustible substances

thermal-conductivity

calorific value

The fi re 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 complex ity 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 eventuali ty. 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 the

specified test conditions.

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

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

Addi tives can influence the resultand must be considered separately.

Further details are to be found in oursafety data sheets.


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43

Index of key terms

43

A

Abrasion 25

Acid and alkal i solut ions 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 36

saturated 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 servicetemperature 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

Tensi le strength 14

Thermal conductivity 29

Thermal data 29Thermal 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


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Documents

Elastollan Material PropertiesR1