Di-azides cross-linked, iPP/EPDM-based thermoplastic vulcanizates

Two di-azidoformates: 4,4′-isopropylidenediphenyl azidoformate (4,4′DAF), and tri(ethylene glycol)-di(azidoformate) (GDAF), and one di-sulfonyl azide: 1,3-benzenedisulfonyl azide (1,3BDSA), are investigated as cross-linking agents for iPP/EPDM-based dynamically vulcanized thermoplastic vulcanizates (TPVs). Their performance is compared with TPVs cured with peroxide, alone and in combination with a coagent. The di-azides proved already to be effective curing agents for EPDM-rubber in static conditions in a previous study. With respect to the production conditions of the investigated TPVs, the reaction temperature of the sulfonyl azide makes it the most suitable cross-linking agent. Exceptionally good mechanical properties are obtained with very low 1,3BDSA loadings. The results indicate that, in the 1,3BDSA cross-linked TPVs the EPDM-rubber particles size significantly change with the curative concentration.