Effect of particle size and surface treatment on constitutive properties of polyester-cenosphere composites

Cenospheres (hollow, aluminum silicate spheres ranging from 10 to 400 mum in diameter) are used as filler in a homogeneous polyester composite. Particle size was varied to study its effect on mechanical properties of the composite. The effect of particulate surface modification using a silane coupling agent was also studied. Properties of the composites were characterized using standard testing methods. When compared to the largest particulate used, an increase in compression strength was achieved by particle size reduction and use of coupling agent. The Elastic modulus increased by using fine particles, while Poisson's ratio remained constant and independent of silane treatment or particle size. Fracture toughness increased with particle size reduction and increased further with silane surface modification. Dynamic compressive strength increased with particle size reduction, while silane did not show improvement. The addition of cenospheres as well as silane treatment increased the glass transition temperature for polyester. A given mass fraction of particulate, of a mean diameter D, will have the surface area between the particulate and matrix scale as D-1 (specific surface area). The sensitivity of these properties to cenosphere size is a direct function of the interfacial surface contacts between the polyester and the cenospheres and the specific surface area. (C) 2002 Kluwer Academic Publishers.