Mechanical properties of PVC/SBR blends compatibilized by aerylonitrile-butadiene rubber and covulcanization

The mechanical properties of poly(vinyl chloride) (PVC)/styrene-butadiene r ubber (SBR) blends compatibilized by acrylonitrile-butadiene rubber (NBR) w ere studied. A sulfur curing system was employed to crosslink the rubber of the blends. In the case of the blends without any curing agents, an increa se in NBR content did not improve the tensile strength and elongation-at-br eak However, a significant improvement in the mechanical properties was obs erved when NBR was added as a compatibilizer and the blend was vulcanized. In the PVC/NBR/SBR (50/10/40) blends, the tensile strength and elongation-a t-break increased with an increase in sulfur concentration. This improvemen t was attributed to covulcanization between NBR and SBR. The fracture tough ness of PVC/NBR/SBR (50/10/40) blends was characterized by the critical str ain energy release rate, G(C). In the case of the PVC/NBR-29/SBR (50/10/40) blends, an increase in sulfur concentration resulted in a dramatic increas e in G(C). However, the G(C) value of PVC/NBR-40/SBR (50/10/40) blends decr eased with an increase in sulfur concentration owing to the brittle behavio r of one of the blend components-the PVC/NBR-40 (50/10) phase.