Poly(n‐Butyl acrylate)/polystyrene interpenetrating polymer networks and related materials. II. Aspects of molecular mixing via modulus‐temperature studies

Abstract

Abstract The glass transition, rubbery modulus, and tensile behavior of poly(n‐butyl acrylate)/polystyrene interpenetrating polymer networks (IPN's), semi‐1 IPN's, and their corresponding random copolymer networks were studied as a function of both composition ratio and crosslink density. Two temperatures were selected for analysis: 25°C, halfway between the two transition temperatures, and at 160°C., in the rubbery plateau region. The modulus data at 25°C were compared with wellknown composite models. The moduli of the IPN's and semi‐1 IPN's lie close to the Davies model in the polymer II rich region but follow the Budiansky model in the polymer I rich region. In one interpretation of the Coran‐Patel model, a phase inversion takes place around ϕ 2 = 0.8, which is higher than the composition at which the phase connectivity of polymer II begins to appear, ϕ = 0.5, via electron microscopy studies. The rubbery modulus behavior of the full and semi‐1 IPN's follow the equation of Siegfried, et al. reasonably well, which considers the deformation effect of polymer I in terms of the rubber elasticity front factor. The stress‐strain behavior of both the full and semi‐1 IPN's was similar to that of toughened plastics at polymer II rich compositions, and to that of reinforced elastomers at polymer I rich compositions.