Dimensional recovery of cold‐rolled polycarbonate

The dimensional recovery of cold‐rolled polycarbonate was measured between 100 and 147°C, and compared to stress‐relaxation data. The strain‐recovery isotherms were superimposed to produce a master curve which could be represented by a distribution function, U (τ), termed the strain recovery spectrum. U (τ) is found to be nearly identical to the relaxation spectrum, H (τ), calculated from the stress‐relaxation master curve; and the shift in U (τ) as a function of temperature, WLF shift factor, is similar to that obtained from other viscoelastic measurements on polycarbonate. For the deformations studied, 25 and 50% reduction in thickness, the recovery behavior is found to be independent of strain (linear), suggesting that nonlinearity in a polymer glass results from large stresses, and not from large strains.