Mechanical and dielectric relaxation of crystalline polymers in relation to degree of crystallinity and morphology

Abstract

Mechanical and dielectric relaxation as related to the morphology of crystalline polymers is reviewed. The behavior with temperature of the imaginary part of the complex dielectric constant and the mechanical loss factor, tan δ, at constant frequency is discussed in detail for two typical crystalline polymers: poly(chlorotrifluoroethylene) and polypropylene. Three relaxations are typically observed: a low temperature relaxation occurring at temperatures below the dilatometric glass transition temperature; a glass temperature relaxation occurring near the glass transition temperature; and a high temperature relaxation occurring between the glass temperature and the melting point. The activation parameters are given for these relaxations, and the influence of morphology on them is discussed along with possible molecular interpretations.