Effect of initiating system, blend ratio and crosslink density on the mechanical properties and failure topography of nano-structured full-interpenetrating polymer networks from natural rubber and polystyrene

The mechanical performance of full-interpenetrating polymer networks (IPNs) based on natural rubber/polystyrene (NR/PS) system has been studied in det ail. The IPNs were prepared using different initiators viz,, benzoyl peroxi de (BPO). azo-bis-isobutyronitrile (AIBN), and dicumyl peroxide (DCP) and t he effect of initiating systems on the properties was studied. It was obser ved that in all cases the IPNs initiated using DCP showed a superior proper ty compared to BPO and AIBN initiated ones. The crosslink density of the IP N was varied by varying the percent of divinyl benzene (crosslinking agent of PS) and the effect of crosslink density on the properties has been studi ed. The stress-strain behaviour, tensile strength, Young's modulus, elongat ion at break, tear strength, tension set and tensile set were determined. T he effects of strain rate on tensile properties were analysed. The studies on the morphology using scanning electron microscopy showed an increase in phase mixing on increasing the PS content and PS crosslinking, However, hig h level of PS content and PS crosslinking lead to a decrease in phase mixin g. The morphology studies using TEM revealed the interesting fact that NR/P S IPN system was nano-structured, The fracture surfaces of tensile and tear specimens were studied using scanning electron microscopy, to get a clear picture of the mechanism of failure. (C) 2001 Elsevier Science Ltd. All rig hts reserved.