THERMOPLASTIC ELASTOMERS

Thermoplastic elastomers are crosslinked by secondary valence interactions. They show rubber elasticity at service temperatures but may be thermoplastically processed at elevated temperatures, i.e. they may be injection-moulded or, in special cases, spun from solution. Secondary valence interactions give rise to a continuous crosslink spectrum controlling the segment mobility in its low temperature region but controlling the crosslinking stability in its high temperature region. Crosslinking, which partly breaks down on heating the sample, is restored when the sample is cooled. Consequently, a stress crosslinking may be distinguished from strain crosslinking which is formed on cooling the deformed material, thus stabilizing the deformation. Stress and strain crosslinking systems reflecting the thermomechanical history are seen from shrinkage experiments. © 1979.