Theory of the modulus of crystalline polymers

Abstract

A new theory for the elastic modulus of crystalline polymers has been developed for temperatures above the glass transition. The theory is based upon the assumption that crystallites behave as crosslinks and as a rigid filler. The shear modulus G is given by G = (dRT/M̄_c)F, where F is a factor giving the relative increase in modulus due to the volume of the rigid crystallites. The number‐average molecular weight M̄_c of the amorphous sequences is calculated as a function of degree of crystallinity from copolymer theory. The theoretical values of the modulus as a function of degree of crystallinity agree reasonably well with experimental values over a wide range.