Exploring a Novel Cyclic Monofunctional Peroxide for Curing of Silicone Rubber at Elevated Temperature

The curing characteristics of silicone rubber (polydimethylsiloxane [PDMS]) in the presence of structurally different peroxides, namely dicumyl peroxide (DCP) and 3,3,5,7,7-pentamethyl-1,2,4-trioxepane (PMTO), have been studied in details. At moderate temperature, DCP is more prominent for curing the silicone rubber but at high temperatures it suffers from low scorch safety. An inhibitor 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) was added with DCP to stabilize the radicals in order to increase the scorch safety time. On the other hand, PMTO showed a prolonged scorch safety and better crosslinking efficiency rather than (DCP+TEMPO) mix at higher temperatures. PMTO-crosslinked PDMS shows better crosslinking efficiency as indicated by a higher gel content and low swelling index value. Also the mechanical properties, thermal stability, and dynamic mechanical behavior of PMTO-crosslinked PDMS are much superior than (DCP+TEMPO)-crosslinked PDMS. Apart from thermoplastic vulcanizates (TPVs) made from PMTO-crosslinked PDMS show better physicomechanical behavior compared to the TPVs made from (DCP+TEMPO)-crosslinked PDMS. Moreover, DCP undergoes decomposition reactions at a higher temperature and forms acetophenone, which leads to an unpleasant smell in the final products whereas no such phenomenon is observed for PMTO. Therefore, PMTO turns out to be the suitable peroxide for crosslinking of PDMS at higher temperature. (C) 2016 Society of Plastics Engineers