Relation between stress-relaxation studies and dynamic properties of polyisobutylene

Abstract

Experimental results on stress-relaxation modulus Er(t) and complex dynamic modulus E′(ω)+iE″(ω) of polyisobutylene are now available in the literature. To cover the entire time scale, the effect of changing the temperature of measurement is assumed to be equivalent to a linear change of the time scale. According to the general theory of linear viscoelastic behavior, the functions Er, E′, and E″ can each be computed from any one of them. This is qualitatively correct. The data on E′ in the transition region can be represented by the Gauss Error Integral form of equation used by Bischoff, Catsiff, and Tobolsky for E r of several polymers. The "wedge-box" distribution function proposed by Tobolsky is also compared with the experimental data and shows a reasonably good agreement with experimental results over the entire time scale.