Stress relaxation in polycarbonates

Abstract

A procedure is presented for investigation of stress relaxation in various brands of foreign and domestic polycarbonates in different stages of loading. This study is the first to cite results of experimental investigations of stress relaxation in carbonates subject to long-term tests at a constant strain rate. The results are then processed statistically, and stress‐relaxation curves are constructed, and the latter analyzed and mathematically described. Model representation of stress relaxation in polycarbonates has made it possible to determine the time required for stress relaxation. In addition to such basic advantages as high resistance to aggressive media, atmospheric effects, etc., polymeric materials possess a number of disadvantages: low heat stability and thermal resistance, and tendency to creep and stress relaxation. Relaxation is a physical process whereby a system goes over into an equilibrium state, and is sufficient to have altered external energy conditions. As applies to polymeric materials, the rate of relaxation and its intensity will depend on their chemical and physical structure, intermolecular interaction, and parameters of the external energy field (temperature, mechanical stress, amplitude and frequency of loading, etc.). Stress relaxation during constant deformation is described,