The effect of the environment on the stress crazing of polycarbonate

Abstract

The effect of a number of different liquids on the rate of crazing of polycarbonate was studied. It was found that liquids either had no effect on the mechanical response, caused immediate cracking and fracture or caused a measurable rate of crazing, depending on the solubility parameter of the liquid. The rate of crazing in those liquids that caused crazing was found to vary inversely with the square root of time, indicating that diffusion through the end of the craze controlled the craze growth. Pre-immersion in one of the solvents, ethanol, had a strong effect on the subsequent rate of crazing under a constant load. The pre-immersion of pre-cracked samples initially caused an increase in rate of crazing. After a pre-immersion time of roughly 24 to 72 hours, the subsequent rate of crazing decreased with an increase in pre-immersion time. When the pre-immersion was conducted on an uncracked specimen and the crack was generated after the pre-immersion, the subsequent rate of crazing increased steadily with pre-immersion time. An explanation for the observed results is given.