Effects of interfacial adhesion on the rubber toughening of poly(vinyl chloride) Part 1. Impact tests

The influence of interfacial adhesion on the impact toughness of poly(vinyl chloride) (PVC)–nitrile rubber (NBR) blends with the morphology of well-dispersed rubber particles has been investigated. The blend containing NBR 18 (NBR with 18 wt% acrylonitrile (AN)) has medium interfacial adhesion strength, and exhibits a brittle–ductile transition at a critical matrix ligament thickness Tc=0.059 μm while the blend containing NBR 26 (NBR with 26 wt% AN) and having stronger interfacial adhesion exhibits the transition at Tc=0.041 μm. The difference can be understood in terms of the deformation mechanisms. Debonding at the interface of the PVC–NBR 18 blend takes place upon impact, and this induces shear yielding of the matrix. For the PVC–NBR 26 blend, however, no microvoid is formed, so the occurrence of matrix shear yielding is delayed. In the investigated rubber particle size range (0.04−0.12 μm), debonding followed by matrix shear yielding is a much more important toughening mechanism than internal cavitation of rubber particles.