An experimental study of the effect of rubber particle dispersion on the brittle ductile transition of polyvinyl chlorde (PVC)/nitrible rubber (NBR) blends is carried out based on the model of pseudonetwork morphology established in our previous paper.However

two well separated master curves of brittle ductile transition for blends with the morphology of well dispersed rubber particles and with the pseudonetwork morphology were obtained

indicating that the rubber particle dispersion has a great influence on the brittle ductile transition of PVC/NBR blends.The critical matrix ligament thickness for the blends with the morphology of well-dispersed rubber particles is much smaller than that for the blends with the pseudonetwork morphologyy.Therefore

the pseudonetwork morphology is much more efficient in the rubber toughening of PVC than that of well-dispersed rubber particles.The present study strongly supports that the critical matrix ligament thickness is not noly a material property of polymer maxtrix

but it is also a function of interfacial adhesion and rubber particle configuration.