HIGHLY FILLED THERMOPLASTIC COMPOSITES .2. EFFECTS OF PARTICLE-SIZE DISTRIBUTION ON SOME PROPERTIES

The effect of irregularly shaped glass particle size and size distribu tion on the packing density and flexural mechanical properties of high ly-filled composites with a rubbery thermoplastic matrix was studied. Increasing the particle's median size and size distribution width sign ificantly increases the packing density of the composites. Compression molding causes the glass particles to fracture at a decreasing level with an increasing distribution width. Particle median size, rather th an size distribution, affects the mechanical properties; The flexural modulus and strength increase and the ultimate deflection in flexure d ecreases with a decreasing median size. A ''glass network'' is formed in the compression molded composites because of the mechanical interlo cking of particles. The nature of this continuous glass phase predomin ates the composites mechanical behavior. The particle's size and shape determine the nature of the glass network and, thus, have a dominatin g effect on the mechanical properties. The latter are significantly af fected by the particle's surface properties. A specific silane treatme nt of the glass particles acts to reduce the particle/particle frictio n, resulting in a higher packing density. The treatment also acts as a cohesive liquid to increase the strength of the glass network, and to increase the particle/polymer adhesion, increasing the composites' st rength and ductility.