Thermoplastic Elastomers (TPE)
Properties and Applications
Thermoplastic elastomers (TPE) are very flexible, low modulus polymeric materials that can be stretched at room temperature to at least twice their original length without noticeable permanent deformation, but can be plastically deformed or recast like ordinary thermoplastics at elevated temperatures. Thus, thermoplastic elastomers resemble vulcanized rubbers except that the network of chemical crosslinks is replaced by one of physical crosslinks.
Most thermoplastic elastomers are block copolymers consisting of both elastic and rigid blocks. The elastic blocks have typically a much higher molecular weight than the hard segments. The latter self-agglomerate to glassy and reinforcing domains that prevent plastic deformation but allow for elastic deformation of the flexible blocks. However, when TPEs are heated to the melting or softening temperature of the hard segments, they can be plastically deformed.
Some major high volume TPEs include SBS, SIS, SEBS, TPUs as well as polyamide and polyester silicone rubbers. The glass transition temperature (Tg) of the soft segments is well below room temperature whereas the Tg of the hard segments can vary between 95 and 250°C. The latter determines the upper service temperature of the TPE.
TPE elastomers are used for a wide varriety of applications in many markets. Typical products include footwear, hydraulic gaskets, synthetic leather, building materials, caster wheels, automotive instrument panels, power tools, drive and timing belts, outer cases of electronic devices, and sporting goods.