Polymer molecular structure and mechanical properties

Abstract

The theoretical problem of relating the mechanical properties of a polymer to molecular structure is considered for the simplest case where an amorphous polymer is subjected to a hydrodynamic stress system at high rates of deformation. The theoretical basis is that under such conditions the mechanical properties can be attributed to the London forces between nearest atoms on neighbouring chain molecules.

For the amorphous polymers polymethylmethacrylate and polystyrene the calculations give room temperature values of maximum bulk modulus, triaxial and uniaxial brittle fracture strengths and probable brittle fracture strain. Theoretical values of bulk modulus are also obtained for polyethy-lenes of various degrees of crystallinity by considering strain in the amorphous regions only.

It is indicated how time dependent or viscoelastic effects might be introduced into the analysis to describe mechanical properties at much lower rates of deformation.