FRACTURE AND IMPACT STRENGTH OF POLY(VINYL CHLORIDE) METHYL METHACRYLATE/BUTADIENE/STYRENE POLYMER BLENDS/

The Izod impact strength of poly(vinyl chloride)/methylmethacrylate/bu tadiene/ styrene(PVC/MBS)polymer blends can be changed significantly w ith different levels of MBS and/or MBS particle size. The following re sults were obtained by investigating the fracture of PVC/MBS test spec imens: 1) The dependence of the Izod impact strength of PVC/MBS blend on MBS particle size confirms a maximum around a MBS particle size of 2000 Angstrom. When MBS particle size is smaller than 2000 degrees, th e Izod impact strength increases with MBS particle size, and crazing o ccurs mainly in this region. When MBS particle size is larger than 200 0 Angstrom, then the Izod impact strength, in contrast, decreases with increasing MBS particle size, and both crazing and shear yielding occ ur, mainly in this region. 2) Tensile experiments of PVC/MBS blends ca rried out under various conditions showed that the amount of energy ab sorption increases with decreasing MBS inter-particle distance and wit h increasing MBS particle size when crazing is the main energy absorbi ng mode. The MBS inter-particle distance dominates the energy absorpti on when shear yielding is the main energy absorbing mode. 3) Therefore , the Izod impact strength of PVC/MBS blends and the maximum around a MBS particle size of 2000 Angstrom can be explained as follows: Below 2000 Angstrom, the energy absorption by crazing dominates the total en ergy absorption, and the energy absorption by crazing increases with M BS particle size. Above 2000 Angstrom, the energy absorption by shear yielding is dominant, and the energy absorption by shear yielding incr eases with decreasing inter-particle distance, that is to say, decreas ing MBS particle size.