Stress Cracking of Plastics by Gasoline

The susceptibility of polycarbonate, poly (methyl methacrylate), and cellulose acetate butyrate to gasoline-induced stress cracking was evaluated by measuring the critical strains of specimens exposed to a variety of commercial gasolines and gasoline components. In general, the critical strain decreased and the severity of cracking of molded parts increased as the aromatic content of the gasolines increased. However, low molecular weight aliphatics as well as specific aromatic components did also markedly reduce critical strain. The effects of sample geometry, temperature, and weathering on critical strain were determined. The capability to predict the critical strain of polymers in the presence of complex liquid mixtures on the basis of physical constants of pure liquid components was examined.