Influence of processing parameters and molecular weight on the mechanical properties of PVC

The role of a variety of processing parameters in determining the mechanical properties of solid PVC has been examined. Annealing pretreatment has been shown to increase both the yield stress and the modulus. It was found that the density of the material similarly increased as the annealing progressed, and when the density reached a limiting value, the yield stress and modulus also reached a limiting value. The molecular weight of the resin, as measured by its intrinsic viscosity, also affected the various mechanical properties measured. However, the yield stress increased while the modulus decreased as the molecular weight increased. This unusual behavior was thought to be a secondary effect. Finally, the addition of increasing amounts of stabilizer to the PVC resin resulted in an increase in modulus and a decrease in yield stress. This was consistent with a model for plastic deformation in which the stabilizer acted as small hard particles. The activation strain volume did not change with different concentrations of stabilizer, further supporting a model for a two‐phase structure.