Thermoplastic elastomers

There are four types of elastomers:
- Olefinics, Styrenics, Polyurethanes, and polyesters

a) Olefinics (TPOs are used for bumper covers on cars)

Produced by blending copolymers of ethylene and propylene (EPR) or ter polymer of ethylene-propylene diene (EPDM) with PP in ratios that determine the stiffness of the elastomer

A 80/20 EPDM/PP ratio gives a soft elastomer (TPO)

b) Styrenic thermoplastic elastomers (STPE)

- Long triblock copolymer molecules with an elastomeric central block (butadiene, isoprene, ethylene-butene, etc.) and end block (styrene, etc.) which form hard segments.

- Other elastomers have varying amounts of soft and hard blocks

c) Polyurethanes

- Have a hard block segment and soft block segment

Soft blocks corresponds to polyol involved in polymerization in ether based

Hard blocks involve the isocyanates and chain extenders

d) Polyesters are etheresters or copolyester thermoplastic elastomer

Soft blocks contain ether groups are amourpous and flexible

Hard blocks can consist of polybutylene terephthalate (PBT)