Thermal and mechanical properties of silane-grafted water crosslinked polyethylene

The effects of linear low density polyethylene (LLDPE) grafting with vinyltrimethoxysilane by different types and contents of peroxide were studied. When grafting silane onto LLDPE, with 0.10 phr of Dicumyl peroxide (DCP) or 0.05 phr content of 2,5-Dimethyl-2,5-di (tert-butyl-peroxy)-hexane (DHBP), it was found that the grafting effect was improved; however, as Di(2-tert-butylperoxypropyl -(2))-benzene (DIPP) or excess DHBP was used, LLDPE was supposed to cause self-crosslinking, which reduced the grafting effect of silane and was invalid in the processing of extrusion. In this study, vinyl trimethoxysilane (VTMS) was grafted onto various polyethylenes (HDPE, LLDPE, and LDPE) using DCP as an initiator in a twin screw extruder. The grafted polyethylenes were able to crosslink utilizing water as the crosslinking agent. The effects of varied crosslinking time on the mechanical properties of the crosslinked polyethylenes were studied. It was found that the HDPE and LLDPE were apt to crosslink during the grafting process and thus decreased the grafting ratio. Multiple melting behavior was observed for crosslinked LDPE and LLDPE. Mechanical and thermal properties of the crosslinked PE are much better than that of uncrosslinked PE. (c) 2005 Wiley Periodicals, Inc.