Studies on polybutadiene rubber (PBR)-polystyrene (PS) interpenetrating polymer networks

Abstract

Elastomer-plastomer blends based on polybutadiene rubber (PBR) and polystyrene (PS) giving interpenetrating networks (IPNs) were studied. The semi IPNs were formed by allowing the initially formed elastomer (PBR) network to swell in styrene monomer and then completing polymerization of the monomer through the swollen elastomer network. For full interpenetrating network formation selected low doses of divinylbenzene (DVB) was used in the monomer styrene and copolymerization of the styrene-DVB system through the monomer swollen elastomer network was effected subsequently. Dicumyl peroxide (DCP) was used to form the initial PBR network and benzoyl peroxide (Bz2O2) was used as the initiator for the polymerization of styrene or styrene-DVB mixture. Effects of variation of DCP dose, DVB dose and PBR-PS blend ratio on the physical-mechanical properties of the blends were examined. The full IPNs exhibited higher tensile strength and modulus while the semi IPNs exhibited greater toughness. A PBR-PS blend ratio of around 50∶50 to 40∶60 resulted in blends morphologically characterized by spherical domains of PBR encompassed by PS phase appearing fibrillar in nature and a synergism in the toughness property was most prominent in blends of this blend ratio range. For PBR>50%, the elastomer phase is apparently the continuous phase, while it is just the reverse for PBR<40 to 50% in general.