While the development and use of particulate fillers has been prevalent for decades, few systematic studies have sought to explore the many variables that effect the structure-property relationships in these systems. This work examines average filler size, size distribution, particle shape, loading, coupling agents and crosslink density of particulate filled systems using a model system of alumina particles in an epoxy matrix.
In general, the cured properties of the filled composites were robust. Small changes in particle size, shape, and size distribution had little impact on the resulting properties. Resin crosslink density and filler loading were the most critical variables, causing changes in all properties. It was determined that specimen fracture occurred at the filler interface due to a weak epoxy-alumina interaction.
Interfacial adhesion between alumina and epoxy was explored with the use of silane coupling agents. The size and quality of the boundary interlayer was probed. It was determined that the chemical nature and structure of the interlayer affected the mechanical properties and fracture properties of the bulk matrix.
As fillers continue to be used in practical systems as well as developed into novel functional gradient materials, it is critical to be able to define the effects of fillers. This work highlights that the polymer matrix remains the foremost variable while the ability to tune and predict the interaction between filler and matrix is very important.
