Dependence of solvent crazing in bisphenol–A polycarbonate on molecular weight of organic liquids

Solvent crazing has been investigated for bisphenol-A poly-carbonate exposed to the liquids of n-alcohols, di-n-alkylphthalates, and adipic acid polyesters. The critical strain at which crazes appeared was determined with a Bergen elliptical strain device. In the case of the n-alcohol and di-n-alkylphthalate liquids with a small number of carbons in the alkyl chain, crazes spread rapidly to areas of lower strain with time and ceased within 30 min at room temperature. Such a lower limiting value of critical strain can be predicted by using polar-nonpolar solubility parameter plotting representations employing the molar volume term. On the other hand, craze initiation was more delayed for two higher molecular weight liquids, di-n-octylphthalate and adipic acid polyester. Sorption studies were also conducted on polycarbonate immersed in both liquids. The values of the activation energy and diffusion coefficient estimated from the experimental data on craze initiation were found to be nearly comparable with the ones from the sorption experiments. In conclusion, the induction time-that is, the time at which crazes appear for a given strain–is controlled by the diffusion of the crazing liquid into the polymer. Thus, in the case of these liquids, which are miscible with the polymer, the crazing mechanism can be explained in terms of facilitated craze formation of a plasticized polymer.