The effect of filler particle-size distribution in epoxy casting formulations

Abstract The selection of particle size distribution is based on a theoretical concept of the “close packing” of particles. The usefulness of this concept was investigated using silica as the filler in a single epoxy‐hardener system. The viscosity and settling characteristics for several particle‐size distributions and concentrations of silica fillers were studied. These studies show that significant decreases in the viscosities of casting formulations can be obtained using a two‐component filler system which permits the use of higher filler loadigs. The increase in the ratio of coarse filler to fine filler reduced the flexural strength of the castings and increased the rate of settling in the formulations. The effect of parameters other than particle size is demonstrated by the use of non‐silica fillers.