Further Dynamic Investigations on Polymers

Abstract

Using the vibration tester of The Franklin Institute, a check of the proportionality between stress and strain in dynamic testing disclosed that a proportionality exists when heating is eliminated. A comparison of values of the dynamic test and steady‐state experiment in the same range of rates of shear and shearing stress showed that the behavior is basically different; whereas in the dynamic test the viscosity is independent of both amplitude and shearing stress, in the steady‐state test experiment a very high dependence exists. The curve of viscosity vs rate of shear (D) is very similar to the one of dynamic viscosity vs frequency (f). A frequency shift of the order of two is involved in comparing D and f. The application of Ferry's method of reduced variables to a polyisobutylene solution, liquid polyesters, and solid plastics showed its validity. A precision test on the polyester showed that the temperature shift, Tρ/T_0ρ0, is necessary to make experimental values at different temperatures fit. The reduced curve of G′ vs frequency for different plastics has an S shape with different slopes in a very wide range of frequency around 10²⁴.