VISCOELASTIC MELT BEHAVIOR OF POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE), HIGH-IMPACT POLYSTYRENE, AND A 35-65 BLEND

The viscoelastic melt behavior of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO resin), high‐impact polystyrene (HIPS), and a 35–65 blend of these polymers has been characterized by measuring the steady shear viscosity and primary normal stress difference and the dynamic storage and loss moduli as functions of shear rate or frequency and temperature. Time–temperature superpositioning was used to generate master curves of each type of data for a reference temperature of 260°C. This procedure required five different empirical shift factors for each material. These shift factors show large differences between PPO resin and HIPS and exhibited large deviations from the WLF equation with universal constants. This result suggests that the temperature dependence of the relaxation processes in PPO resin is significantly different from the temperature dependence of HIPS relaxations. Flow activation energies computed from the viscosity data for PPO resin are much higher and more shear sensitive than those calculated for HIPS. The computed relaxation spectra clearly display the effect of long‐time relaxation mechanisms associated with PPO molecules when compared to HIPS. The 35–65 blend exhibits general rheological compatibility with material parameters and responses intermediate between PPO resin and HIPS. This result is indicative of a high degree of segmental mixing for the two components in the blend. Copyright © 1979 John Wiley & Sons, Inc.