CROSSLINKING METALLOCENE-BASED POLY(ETHYLENE OCTENE) COPOLYMERS 'EOM' USING NOVEL HIGH PERFORMANCE 'HP' DIALKYL PEROXIDE FORMULATIONS

摘要

"HP" (High Performance) Dialkyl peroxide formulations based on; dicumyl peroxide, m/p-di(t-butylperoxy)diisopropyl benzene and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane were evaluated, for the crosslinking of metallocene-based poly(ethylene octene) copolymers [EOM], compared to the standard peroxides. The octene content in the copolymers ranged from 9.5 to 28 wt.%. The HP peroxides provided a dramatic 100% increase in productivity when crosslinking poly(ethylene octene) "EOM" at a 10℃ higher cure temperature. Elevated cure temperatures were possible, since these HP peroxides provide an important delay in cure activity during the initial stage of the crosslinking process, with no sacrifice in total cure time. Typically increasing the cure temperature of a conventional polymer-peroxide blend will result in unwanted crosslinking or "scorch". Concomitantly, the HP type peroxides provided a 30% increase in crosslinking efficiency with equivalent to better physical properties for the final crosslinked EOM copolymer. The HP peroxides also provided crosslinked EOM with improved thermal stability, based upon the low compression set data at 150℃. Low compression set is an important criterion for O-ring, hose, belt and gasket profile applications. A moving die rheometer (MDR) and a dynamic mechanical analyzer (RPA) were used to determine the relative degree of crosslinking, scorch times and crosslinking rates with respect to temperature.