Shear yield and crazing stresses in selected glassy polymers



The plane strain shear yield stress and the triaxial crazing stress were determined for several commercial glassy polymers as a function of temperature. The polymers considered were: polycarbonate (Lexan®), polysulfone (Udel®), polyetherimide (Ultem®), polyarylate (Arylon®), and an amorphous nylon (Zytel® 330). When normalized to Tg the data for the various polymers were similar but not identical. An exception may be the triaxial crazing strains. In the temperature region between [T–Tg] = −300° and −50°C the crazing strains were all small (<1.5%), showed little temperature dependence, and appeared identical within the precision of our measurements. For temperatures below Tg and above any major secondary relaxation, Poisson's ratio was found to be constant for all of the polymers examined, 0.42 (±5%). © 1993 John Wiley & Sons, Inc.