Morpholgy and Tg behavior of Polyurethane-Polystyrene Semi-IPN's and Linear blends

Abstract

Semiinterpenetrating polymer networks (semi-IPN’s) and linear blends of polyurethane and polystyrene were prepared under high pressure to compare with full IPN’s and to evaluate the effect of interpenetration in IPN synthesis. The morphology, dynamic mechanical properties, and density behavior were analyzed to determine the effect of synthesis pressure and the effect of interlocking on the degree of intermixing of the component polymers. The degree of intermixing increased with increasing synthesis pressure, and the relative degree of intermixing among IPN, semi-IPN, and linear blend was in the following order. IPN > semi-I IPN (PU cross-linked/PS linear) > semi-II IPN (PU linear/PS cross-linked) = linear blend. The morphology also showed a similar trend in the electron microscopy study. The relative degree of intermixing depended on the mobility of the polymer component having linear structure. Thus when PU component was made linear, the resulting semi-II IPN showed a higher degree of phase separation compared to semi-I IPN the which the relatively immobile PS component was linear.