THERMAL-PROPERTIES OF SILANE AND PEROXIDE CROSS-LINKED POLYETHYLENE, ETHYLENE-PROPYLENE RUBBER AND THEIR BLENDS

The effect of silane and dicumyl peroxide (DCP) induced crosslinking, as well as the effect of annealing on the thermal properties and struc tural parameters of polyethylene (PE) and its blends with ethylene pro pylene rubber (EPR) have been studied by differential scanning calorim etry (DSC) and X-ray diffraction analysis. The reduction in the meltin g point, melting endotherm and percent crystallinity is greater in the case of DCP crosslinking and is also dependent on the degree of cross linking. For all compositions the percent crystallinity increases and the interplanar distance (d and R values) decreases on annealing. Crys tallization and fusion behaviour of crosslinked polyethylenes are mark edly dependent on the sol (extractable) content and the effective netw ork density of the gel. The dynamic modulus (E') and loss factor (tand elta) have been determined over the entire temperature range of meltin g by dynamic mechanical thermal analysis (DMTA). Silane crosslinked sy stems show higher dynamic modulus at high temperature. Unique characte ristics and better high temperature properties of silane crosslinking systems have been explained by the formation of a dense tetrahedral ne twork structure.