SHAPE-MEMORY EFFECT OF DEHYDROCHLORINATED CROSS-LINKED POLY(VINYL CHLORIDE)

Crosslinked poly(vinyl chloride) (CPVC) samples with various extent of dehydrochlorination x, exhibiting a shape memory effect, were prepare d. Tn order to determine the optimal structure for the shape memory ef fect, electron microscopy, dilatometry, differential thermal analysis (DTA), thermal conductivity and tensile strength measurements were per formed. The extremum of all the measured physical properties was found for the sample with x = 12%, corresponding to the optimal structure. The characteristic parameters of the expansion process were calculated from the fits of the experimental data. The extremum was qualitativel y predicted by simplified quantum chemical models of a double PVC chai n using the semiempirical AM1 method. The generalized zip mechanism of CPVC dehydrochlorination might explain the extremum due to mutual cha in reorientation with increasing x.