Thermoplastic elastomers are plastics that at room temperature are comparable to classical elastomers, but can be plastically shaped if heat is supplied,
and thus exhibit a thermoplastic behaviour.
“Normal elastomers” are three-dimensional chemically cross-linked network molecules with a wide spacing. The cross-links cannot be undone without breaking down the material.
Thermoplastic elastomers have physical cross-linking points in certain areas (secondary valence forces or crystallites) that dissolve under the effect of heat without breaking down the macromolecules. They can therefore be processed much better than normal elastomers. Plastic waste can also be remelted and further processed.
However, this is also the reason why the material properties of thermoplastic elastomers vary nonlinearly over time and temperature. The two essential measurable physical material properties are the compression set and the stress relaxation. Compared to ethylene propylene diene rubber (EPDM) they have worse material properties in their short-term behaviour, and the raw material is also more expensive. In long-term behaviour,
however,the picture is reversed relative to EPDM.
Due to the very short cycle times in production because of the handling process similar to that for plastic, thermoplastic elastomers are finding increased use
in body seals for automobiles.