Effect of morphology on the brittle ductile transition of polymer blends: 3. The influence of rubber particle spatial distribution on the fracture behaviour of poly(vinyl chloride) nitrile rubber blends

摘要

Poly(vinyl chloride) (PVC)itrile rubber (NBR) blends with the pseudonetwork morphology and the morphology of well-dispersed particles were prepared to elucidate the influence of rubber particle spatial distribution on the fracture behaviour of the blends. The main toughening mechanism of PVC/NBR blends is matrix shear yielding, irrespective of rubber particle spatial distribution. However, the particle spatial distribution has been experimentally observed to considerably affect the toughness and fracture behaviour of the blends. The blends with the morphology of well-dispersed particles upon impact deform uniformly, while the blends with the pseudonetwork morphology yield preferentially in the pseudonetwork band phase. The pseudonetwork cores deform much less easily than the pseudonetwork bands. The experimental results also confirm that the NBR rubber particles act as stress concentrators to promote shear yielding of PVC respectively in the pseudonetwork bands and in the blends with the morphology of well-dispersed particles. The fractographic analysis on the blends with the above two types of morphologies provides experimental evidence for the suitability of our models for these morphologies that emphasize the roles of rubber particle spatial distribution and matrix ligament thickness. (C) 1998 Elsevier Science Ltd. All rights reserved. [References: 45]