Effects of interfacial adhesion on the rubber toughening of poly(vinyl chloride) Part 2. Low-speed tensile tests

The influence of interfacial adhesion on the tensile properties, including toughness, of poly(vinyl chloride) (PVC)-nitrile rubber (NBR) blends with t he morphology of well-dispersed rubber particles has been investigated usin g two types of blends. The first type, which contains NBR26 (NBR with 26 wt % acrylonitrile (AN)), has a higher interfacial adhesion strength than the second type that contains NBR18. The secant modulus and yield stress of the blends were found to be independent of interfacial adhesion. On the other hand, the elongation-at-break and toughness (defined as the area under the stress-strain curve to break) depend strongly on the interfacial strength. The effects of rubber particle size, size distribution and rubber volume fr action on the tensile properties have been combined into the effect of a si ngle morphological parameter, the matrix ligament thickness T. Both the elo ngation-at-break and toughness increase as T decreases. At T < 0.06 <mu>m t he blends with stronger interfacial adhesion (PVC-NBR26) have much higher e longation-at-break and toughness. Stress whitening was observed in all defo rmed PVC-NBR18 blends. For PVC-NBR26 blends, however, stress whitening occu rred only at T > 0.06 mum Transmission electron microscopy studies revealed that debonding at the PVC-NBR interface is the sole microvoiding mechanism that causes stress whitening. (C) 2000 Elsevier Science Ltd. All rights re served.