The effects of the shape and the surface state of the metallic particles on the electrical, mechanical and thermal properties of metal filled polymeric composites and on the adhesion between metallic filler and polymeric matrix were studied. It was found that there was a marked change of the properties of the composites at a critical volume percent of the metallic particles. The ordinary spherical nickel particles, haying bumpy and equiaxed granuled type of surface, showed a strong adhesion to the PVC matrix and increased the mechanical strength of the composites up to a maximum value at a critical volume percent of metallic particles. However, the irregular plate-like copper particles, having even and flat type of surface, showed no adhesion to the polymeric matrix and decreased the mechanical strength and flexibility of the composites remarkably. In the electrical properties, the nickel particles formed an aggregated continuous conductive metallic network structure in the polymeric matrix at about 5 V/O of metal loading and gave a drastic fall in electrical resistivity, but the copper particles formed a conductive network structure at below 2 V/O of metal loading, even if the same metallic particles size of 7μm was used. The linear thermal expansion coefficients of the composites agreed relatively well with the values predicted by Turner, who suggested a concept of the segregated metallic network formation in metal filled polymeric composite. The metallic particles in the polymeric composite system gave a shift of the glass transition temperature of polymer matrix to a higher temperature in proportion to the surface area of the metallic filler. The SEM study of the fracture surface of the composites manifested the adhesion between the metallic filler and the polymeric matrix.

Keywords: