Viscoelastic behavior of plasticized polyvinyl chloride at large deformations. I. Stress relaxation

Two vinyl chloride polymers with intrinsic viscosities of 0.65 and 1.17 were compounded with four plasticizers. Stress relaxation data were obtained at three temperatures and analyzed by a step function of seven parameters in Maxwell representation. The relaxation times were nearly independent of plasticizer type, plasticizer content, molecular weight, and temperature. The moduli were found to decrease with increasing plasticizer content and/or temperature, the equilibrium moduli being directly dependent on the molecular weight while the delayed moduli were more dependent on plasticizer type. The molecular weight dependence of the equilibrium moduli can be attributed to a participation of the individual chains in several crystalline areas which act as crosslinking points.