Time‐dependent tensile properties. Part III. Microfracture and non‐Fickian vapor diffusion in organic glasses

Abstract

Abstract An attempt is made to outline the mechanisms of “anomalous” vapor diffusions in films of organic glasses. The predominant factor appears to be the diffusion medium's need to relax stresses generated by the osmotic swelling. Diffusion‐induced localization of swelling and drying can create severe compressive and tensile film stresses which promote irreversible changes in film properties. Retardations and accelerations of vapor transport can result from these stresses and strains. The very irregular film swelling and vapor absorption kinetics of the system, phenol Novolac resin‐water, are reported. These reflect both the rapid and slow mechanical response of the relatively brittle, low polymeric films. Isotropic surface microfracture obtained under selective conditions of initial drying are described. The circumstances of this fracture characterize an interesting example of a vapor diffusion‐controlled “crazing.” Although a full understanding of the total behavior is not yet available, the general findings offer a fusion in perspectives of vapor diffusion and tensile fracture in organic glasses.