Abstract
Polycarbonate(PC), a prominent high-performance engineering resin, wes subjected to constant rate tension and compression at temperatures below the glass transition, and its nonlinear plastic flow was analyzed as a stress-aided activation process. The analysis yielded a relation between the activation enthalpy ΔH and the activation entropy ΔS that was in good agreement with the equation between ΔH and ΔS derived from viscoelasticity data from the PC melt. This agreement proves that the structure of solid PC is changed into melt-like structures during the yielding process. The pressure activation volume Δv was always positive, regardless of the change in sign of the hydrostatic component. This was consistent with an unchangeable increase in entropy in the activated state. A possible relationship between the linear plot of ΔH to ΔS and the nonlinear viscosity in polymer melts is briefly discussed.
