Composite Materials Having Low Filler Percolation Thresholds And Methods Of Controlling Filler Interconnectivity

Abstract

Composite materials are disclosed having low filler percolation thresholds for filler materials into the composite matrix material along with methods of controlling filler interconnectivity within the composite matrix material. Methods are, thus, disclosed that provide the ability to control the desired properties of the composites. The composites of the present disclosure are characterized by a "pseudo-crystalline" microstructure formed of matrix particles and filler particles where the matrix particles are faceted and substantially retain their individual particle boundaries and where the filler particles are interspersed between the matrix particles at the individual matrix particle boundaries such that the filler particles form a substantially interconnected network that substantially surrounds the individual faceted matrix particles. In an exemplary embodiment, the composites are formed by selecting matrix particles and filler particles wherein the ratio of the average size of the matrix particles to the average size of the filler particles is about 10 or more. The selected matrix particles exhibit a glass transition temperature. The matrix particles and the filler particles are mechanically mixed and then subjected to a temperature above the glass transition temperature of the matrix particles and a compression pressure for a period of time sufficient to cause the matrix particles to undergo deformation so as to compress them together eliminating void spaces between the particles without melting the matrix material. The method is also demonstrated to work in combination with more standard art methods such as solution mixing for the purposes of achieving additional control of the properties.