What are thermoplastic elastomers?

Thermoplastic elastomers (TPE) are materials, which are thermoplastically processable with rubber-like application properties. Thermoplastic elastomers can be easily formed. They can be manufactured in different hardness ranging from < 5 Shore A to 70 Shore D. Adhesion to nearly all technical thermoplasts can be achived through modification. Their flowability as well as density, optics, scratch resistance and other characteristics, can be adjusted through compounding with different fillers and additives.

 

 

The different TPE types

Thermoplastic elastomers are divided between

TPE       blends       and         block       copolymers



Blends are a composition of a plastics matrix and a soft material like an elastomer.

Block Copolymers are molecular chains, which form into hard and soft segments in the cooling process. There are TPS (thermoplastic styrenic elastomer), TPU (thermoplastic polyurethane elastomer), TPC also known as TEEE (thermoplastic polyester elastomer) and TPA (thermoplastic polyamide elastomer)



The differences between the various TPE types

The various TPE types differ in their properties. For example, TPC has excellent mechanical strength as TPU exhibits very good friction resistance. However, both have improvement potential with the compression set at higher temperatures. TPV and TPS are modifyable at a wide range, though applications with oil and/or high temperatures are a challenge. TPA features a distinctive resiliency, yet it is alike TPU not easily processed,



TPS (thermoplastic styrenic elastomer) on SEBS basis

Styrenic blocks form a physical network

Criteria

Assessment

Hardness

all

Mechanical properties

good

Operation temperature

Max. 100°C, specialized materials up to 150°C

Compression set

40 – 70% at 100°C/24h, specialized materials 41% at 150°C/24h

Oil resistance

limited

Hydrolysis resistance

excellent

Weather-proof

excellent

Processing

excellent

Adhesion

PP, PE, ABS, PC, PMMA, PBT, POM, ...

Others

+ Variability (hardness, adhesion, density, absorbability, CS)

 

+ acid and alkali proof



TPC (thermoplastic polyester elastomers)

Segments of hard polyester and soft polyether

Criteria

Assessment

Hardness

from approx. 80 Shore A

Mechanical properties

excellent

Operation temperature

Up to 160°C

Compression set

80% at 100°C/24h

Oil resistance

good

Hydrolysis resistance

moderate

Processing

excellent

Adhesion

PC, PC/ABS, PET, PBT

Others

+ good dynamic characteristics

 

+ high strength



TPV (thermoplastic vulcanisate, ...)

(PP-EPDM, PP-NR, PP-IIR-Blends)

 

Criteria

Assessment

Hardness

from approx. 35 Shore A

Mechanical properties

good

Operation temperature

max. 100°C

Compression set

40 – 60% at 100°C/24h

Oil resistance

limited

Hydrolysis resistance

Excellent

Weather-proof

Excellent

Processing

Excellent

Adhesion

PP, PA, ABS, ABS/PC

Others

+ rubber-like properties

 

+ dynamic properties

 

- friction

 

- flowability

 

 

TPU (thermoplastic polyurethane elastomer)

 

Criteria

Assessment

Hardness

From approx. 60 Shore A

Mechanical properties

excellent

Operation temperature

Up to 80°C

Compression set

80% at 100°C/24h

Oil resistance

Good

Hydrolysis resistance

Moderate

Weather-proof

Good with aliphatic types

Processing

moderate

Adhesion

PA, PA/ABS, ABS, ABS/PC, PC, ASA, PBT

Others

+ strength

 

+ friction

 

+ tranparency

 

- discoloration (except aliphatic types)

 

 

TPA (thermoplastic polyamide elastomer)

softe polyole and hard polyamide

 

Criteria

Assessment

Hardness

From approx. 75 Shore A

Mechanical properties

excellent

Operation temperature

Up to 80°C

Compression set

80% at 100°C/24h

Oil resistance

Good

Hydrolysis resistance

Moderate

Weather-proof

Good

Processing

Moderate

Adhesion

PC, PC/ABS, PA11, PA12

Others

+ low density

 

+ transparency

 

+ low temperature (up to -40°C)



Shore A versus Shore D

Shore hardness is measured in the resistance against the penetration of a body of a certain shape under defined spring force. The test results range from 0 to 100, where 0 is the least and 100 the highest hardness. The Shore A hardness is softer than Shore D. However, a crossover of both hardness specifications exists. 90 Shore A equals approx. 35 Shore D.

 

 

Multi component technique – what materials are suitable for Adhesion of TPE

Adhesion to certain materials depends on the type of TPE.

 

Type

Adhesion to

TPS

PP, PE, ABS*, PC*, PC/ABS*, PMMA*, PBT*, POM*,...

TPU

PA, PA/ABS, ABS, PC, PC/ABS, ASA

TPC

PC, PC/ABS, PET, PBT

TPA

PC, PC/ABS, PA11, PA12

TPV

PP, PA*, ABS*, PC/ABS*

TPO

PP, PE

*adhesionmodified

 

Various adhesion qualities can occur depending on the material-pairing and their processing.

 

 

The Compression Set (CS)

The compression set determines the permanent set in compression and provides information about the ability of a material to recover after removal of the load. An ideally elastic material will relax completely to the initial thickness, then the compression set will be 0%. On the other hand an absolutely plastic material will not recover at all, then the value is 100%. CS values are important for e.g. sealing or insulation applications.