Highly filled thermoplastic composites .2. Effects of particle size distribution on some properties

The effect of irregularly shaped glass particle size and size distribution on the packing density and flexural mechanical properties of highly-filled composites with a rubbery thermoplastic matrix was studied. Increasing the particle's median size and size distribution width significantly 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 than size distribution, affects the mechanical properties; The flexural modulus and strength increase and the ultimate deflection in flexure decreases with a decreasing median size. A ''glass network'' is formed in the compression molded composites because of the mechanical interlocking of particles. The nature of this continuous glass phase predominates the composites mechanical behavior. The particle's size and shape determine the nature of the glass network and, thus, have a dominating effect on the mechanical properties. The latter are significantly affected by the particle's surface properties. A specific silane treatment of the glass particles acts to reduce the particle/particle friction, 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' strength and ductility.