Composite Interfaces, Vol.8, No.5, 367-381, 2001
Effects of particle size and interfacial slope structure on the mechanical and fracture properties of PVC filled with crosslinked PMMA particles
The effects of interfacial structure and particle size on the mechanical properties of an particulate-filled composite have been investigated using a model system. For this purpose, uncrosslinked and crosslinked poly(methyl methaerylate) particles having the mean size of about 0.8 mum are prepared by a seeded emulsion polymerization, and then the amount and the distribution of crosslink points in the particles are varied. The obtained emulsion particles are powdered by a freeze dry method and dispersed into poly(vinyl chloride) matrix by a melt blending. The uncrosslinked particles are completely dissolved in the matrix due to a good compatibility of poly(methyl methacrylate) with poly(vinyl chloride). In the case of the crosslinked particles, the mutual diffusion of the polymer molecules is restricted within the particle/matrix interfacial regions by the crosslink points. The interfacial structures with different concentration slope dependent upon the amount and the distribution of inner crosslink points are developed with the same particle size. It is found that the yield stress decreases with a decrease in the interfacial adhesion. Furthermore, the effect of particle size is confirmed in the weakest interfacial adhesion system in the range of 0.3-0.8 mum. When the interfacial adhesion is sufficient or the particle size is effectively small, the yield stress was never lower than those of their components.