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 T g 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–T g ] = −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 T g 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.