Abstract
Time-concentration dependence of ultimate properties for polyvinyl chloride-dioctyl phthalate (PVC-DOP) sheets in the rubbery and glassy regions were examined simultaneously with time-temperature dependence at various volume fractions of PVC (v2) ranging from 0.191 to 0.699.
By the time-concentration superposition, the data of tensile strength σb and ultimate strain αb composed respective master curves on a plot of log σbρs/ρ vs. log tb and log (αb-1) vs. logtb, where ρ is weight of PVC per unit volume of the sheet, ρs is a ρ arbitrarily selected as ref6rence and tb is the breaking time observed by the test at a constant strain rate. The shift distance seemed to be equal to those obtained from time-concentration superposition of the tensile creep compliance ρD/ρs. The compliance D2 was defined by the relation, D2=(α-1)/ασ(1-λ0ρ), based on a molecular theory of rubberlike elasticity by Sato, where σ, α denote the tension and the relative extension and λ0 is average degree of contraction of network chains at the natural state. The observed compliance for the specimens of PVC coincided with the above compliance D2 up to very high extension. For smaller extensions α, the relation, D1=(α-1)/ασ, was satisfactory.
The experimental shift distances were larger than those given by the WLF equation, and excessive parts of the distances seemed to be represented by the Arrhenius equation.
A failure envelope was also constructed from these ultimate properties data. The data obtained for the specimens at high v2, however, did not form a single master curve but gave a domain similar to that for natural rubber in time-temperature regions where chrystallization proceeded.
