Dynamic Mechanical Properties of Plasticized Polystyrene-Based Ionomers. II. Melt Rheology

摘要

A high molecular weight styrene ionomer containing 5 mol% sodium methacrylate was blended with a styrene oligomer (MW 800) and investigated by dynamic mechanical techniques. The focus of the study is on the dynamic melt rheology of these materials, whose ratios by weight of ionomer to oligomer are 60/40, 40/60, and 25/75. The glass-transition temperature and ionic transition are first characterized by torsion pendulum measurements as a function of temperature. It appears that a maximum level of plasticization is achieved for the ionic regions, the extent depending on sample history. Time-temperature superposition is obeyed by the blend of 60 wt% ionomer, but not by the other two blends. Relaxations due to the ionic regions are clearly evident in the relaxation spectra of all three blends. Above a particular temperature, the 25 wt% blend indicates an Arrhenius type of dependence.