Thermoplastic vulcanizates by reaction-induced phase separation of a miscible poly(e-caprolactone)/epoxy system

A new method for the prepn. of thermoplastic vulcanizates (TPVs) was successfully applied. Starting with a miscible system of a semi-cryst. thermoplastic polymer and an elastomer precursor, phase sepn. was induced by the increase in mol. wt. during selective crosslinking of the elastomer precursor. As a model system, the semi-cryst. thermoplastic poly(.epsilon.-caprolactone) (PCL) was used in combination with a rubbery epoxy resin based on poly(propylene oxide) (PPOn-epoxy). This approach enables the dispersion of up to 80% of crosslinked rubber in a thermoplastic matrix, providing morphologies that are typical for TPVs. A range in rubber particle size of 0.5-3 .mu.m was obtained by this new method, without the need of blend compatibilization or dynamic processing. The materials exhibit mech. and rheol. properties typical for TPVs and the rubber particles feature a high crosslink d. At high curing temps. and high PPOn-epoxy contents, connectivity of the rubber particles is obsd., which is attributed to the phase sepn. mechanism. Connectivity of the rubber particles has a neg. influence on both the mech. properties and the rheol. behavior.