PVC-DOP系の非線型クリープおよび破壊における時間-温度-濃度換算法則の検討

抄録

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 σ_b and ultimate strain α_b composed respective master curves on a plot of log σ_bρ_s/ρ vs. log t_b and log (α_b-1) vs. logt_b, where ρ is weight of PVC per unit volume of the sheet, ρ_s is a ρ arbitrarily selected as ref6rence and t_b 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/ρ_s. 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.