Environmental stress cracking of glassy polymers and solubility parameters

Abstract

The use of solubility parameters to predict critical stress (σ c * ) or strains (ɛc) for environmental cracking/crazing in several glassy polymers (e.g. PMMA, PPO, PS, PVC, PSF and PC) is re-examined. It is shown that the enthalpic component (χ H ) of the Flory-Huggins semi-interaction parameter (χ) does not always give a good correlation between ɛc and χ H even though solvent molar volume and polymer-solvent molecular interactions have already been considered. Re-analysis of available experimental data using Gent's theory shows that there is a general trend for σ c * (or ɛc) to increase with χ. These results, therefore, support Gent's proposed mechanism of environmental stress crazing/cracking. It is finally concluded that unless a definite relationship can be established between ɛc or σ c * with χ H it is not possible to predicta priori ɛc or σ c * , given the empirical solubility parameters of a solvent. Unfortunately, there are not many such relationships as discovered in this paper.