Uniaxial extension of polyvinyl chloride in the high‐elastic state

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Abstract
The dependence of true stress on the extension ratio of PVC threads has been determined for a wide range of extension rates. Since the polymer subjected to deformation was in the high‐elastic state (at temperatures from 90 to 160°), the deformations were predominantly high‐elastic. The dependence of true stress on the amount of high‐elastic deformation is described by the Mooney‐Rivlin equation.Relaxation moduli have been found on the basis of measurements of stress relaxation at constant deformation after various extension ratios were attained at different rates. Within the limits of deformation regimes at which the true stress is an increasing function of extension ratio the relaxation moduli do not depend on extension ratio and rate of extension. This enables one to arrive at a master curve of the relaxation modulus versus relaxation time with the reservation indicated above concerning the increasing character of the dependence of true stress on extension ratio. The relaxation spectrum represented by the high‐elasticity plateau has been determined from the relaxation moduli according to the first approximation.The experimental data for a very wide range of deformation regimes and temperatures are presented in the form of an invariant dependence of the ratio of true stress to the rate of deformation on the product of deformation time by extension ratio.The ultimate strength of the specimens frozen rapidly after the attainment of definite extension ratios is determined by the accumulated high‐elastic deformation.

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