EFFECT OF MORPHOLOGY ON THE BRITTLE-DUCTILE TRANSITION OF POLYMER BLENDS - 4 - INFLUENCE OF THE RUBBER PARTICLE SPATIAL-DISTRIBUTION IN POLY(VINYL CHLORIDE) NITRILE RUBBER BLENDS

We have derived a new equation for correlating the average matrix liga ment thickness with other morphological parameters of a polymer blend with the pseudonetwork morphology in order to evaluate the effect of r ubber particle spatial distribution on the brittle ductile transition of poly(vinyl chloride) (PVC)/nitrile rubber (NBR) blends. Two types o f rubber particle spatial distributions, i.e. well-dispersed particles and pseudonetwork, are investigated. The formation of PVC primary par ticles favours the toughening of PVC. An approximate master curve of b rittle ductile transition for the blends with the pseudonetwork morpho logy is obtained by plotting the impact strength, versus the average m atrix ligament thickness. The critical matrix ligament thickness for t he blends with the pseudonetwork morphology is 0.11 mu m, which is muc h larger than that (0.059 mu m) for the blends with the morphology of well-dispersed rubber particles. Therefore, pseudonetwork morphology i s much more effective in toughening PVC than the morphology of well-di spersed rubber particles. Moreover, the critical matrix ligament thick ness depends on the rubber particle spatial distribution, and is thus not a characteristic of the PVC matrix. The effects of morphological p arameters and PVC molecular weight on the toughness of PVC/NBR blends are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.