On the solvent stress‐cracking of polycarbonate

Abstract

Abstract The stress‐cracking of polycarbonate by a gaseous or liquid agent results from the diffusion of this agent into the polymer. The low molecular weight polymer fractions and the chain ends within the bulk of the polymer become more ordered during the diffusion and swelling process by their partial solubility in the crazing agent, causing crystallization. The creation of interfaces at areas of order‐disorder causes high shearing forces at this boundary and voids within the bulk of the polymer. These voids are then propagated as crazes or cracks at stresses much lower than the tensile strength of the polymer. Therefore, a stress‐cracking agent need not diffuse rapidly, but must be an effective environment for swelling and/or crystallization. Data from diffusion, density, thermal and molecular analyses are presented to support this mechanism.