Effect of Crosslinking on the Structure, Properties and Failure Mechanisms of XLPE and Crosslinked Butyl Elastomer Blends

Abstract

Abstract The polyblend systems consisting of crosslinkable polyethylene (XLPE) and the crosslinked butyl rubbers were studied. Two types of crosslinked butyl rubbers viz XL-20 (80% crosslinked) and XL-50 (50% crosslinked) were considered in order to find out the effect of crosslinking of the elastomer on the structure, properties and mode of failure of the blends. Properties are correlated with the crystallinity of the blends as determined by X-ray analysis. Both the rate of cure and state of cure are improved by the incorporation crosslinked butyl rubber in XLPE with more advantage in the case of lower crosslinked butyl (XL-50). At the lower level of crosslinked butyl the physical properties and the swelling is governed by the crystallinity of the blend and XL-20 containing blends exhibit lower swelling than XL-50 containing blends. Lower degree of crosslinking in butyl rubber (XL-50) gives rise to more thermally stable blends. Smooth failure is obtained in the case of low degree of crosslinking in the elastomeric phase, viz. XL-50 containing blends. However the fracture in XL-20 containing is accompanied by fibre and cavity formation. Results are discussed considering the structure of butyl rubbers having different degree of crosslinking and a probable mechanism has been put forward.