Influence of Environmental Temperature on Yield Stress of Polymers

Abstract

Uniaxial tension tests under various environmental temperatures are carried out for 5 kinds of polymers: high-density polyethylene(HDPE), poly(vinylidene fluoride)(PVdF), polyoxymethylene(POM), polyamideimide(PAI) and polyether-etherketone(PEEK). As temperature increases, yield stress decreases and yield strain, except in the case of PAI, increases in all of the materials tested. HDPE, PVdF and POM are strongly influenced by environmental temperature, but PAI and PEEK are weakly influenced. The authors previously proposed a spherical model based on intermolecular force(Lennard-Jones type), for understanding the influence of hydrostatic pressure, environmental temperature and strain rate on elastic modulus. In this paper, this model is extended to explain the yield behavior and to propose an experimental equation of yield stress and strain. We found that this equation is useful for describing yield stress under various environmental temperatures.