Physical aging in poly(methyl methacrylate) / poly(styrene‐co‐acrylonitrile) blends. I. Stress relaxation

Abstract

Abstract An investigation was carried out on the effect of physical aging on viscoelastic properties of compatible polymer blends. Poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were chosen for this study. Blends of six different ratios of PMMA and SAN were physically aged at different times and temperatures and then subjected to stress–relaxation tests at small strains. It was found that the shape of the stress‐relaxation curve does not change with a change in blend composition, aging temperature, or aging time. A single “master curve” is presented, to which all data may be fit using 0.408 for the exponential parameter of the Williams‐Watts equation. In creating the master curve, all data are shifted horizontally in time only. For a given set of experimental conditions, the relaxation time τ may be expressed in terms of blend composition, aging temperature, and aging time.