The present investigation was undertaken in order to describe the recovery characteristic of elongation of unplasticized polyvinyl chloride stretched at temperatures above its glass transition point (Tg).
The experimental procedure was as follows; after the specimens have been stretched up to elongation ε1, at temperature T1(>Tg), they were cooled in cold water. They were then annealed at temperature T2(≤Tg) and the recovery of elongation was measured and its values are shown in Figs. 8 and 9.
The data suggested that there was no particular recovery equilibrium in each curve but the strain might recover perfectly after sufficient duration time except at temperatures near the glass transition point or below. Approximate master recovery curves were drawn, as shown in Fig. 10, on the assumption that the method of reduced variables were valid to these experimental results. A simplified expression is also shown of the recovery characteristic derived from the results obtained at definite intervals.
