Fabrication process and electrical behavior of novel pressure-sensitive composites

Abstract

A novel route was developed to fabricate a new pressure-sensitive composite by dispersing homogeneously conductive carbon particles inan insulating silicone rubber matrix. The composites showed a gradual change in electrical resistivity with applied pressure within percola-tion threshold region at a constant temperature. This type of gradual fall of resistivity with applied pressure is very important to fabricatepressure sensors. Various amounts of carbon particles were dispersed in a rubber matrix to understand the effect of volume fraction ofconductive ®ller with applying external pressure on resistivity. A quantitative general effective media /GEM) theory was used to understandthe resistivity of carbon±rubber composites system over a large range of volume fraction of carbon with applied pressure. The use of twodifferent sizes of silicon rubber particles showed a signi®cant effect in gradual fall of resistivity with applied pressure in the narrow range ofpercolation threshold. However, a large variation in resistivity from 1st measuring to 10th measuring was observed. A signi®cant improve-ment in successive measuring of resistivity variation from 1st measuring to 10th measuring was observed when composites were fabricated inhexane solvent media. Finally, nano-sized Al2O3was dispersed to control the resistivity variation upon successive measurement and toimprove the mechanical properties of the composites. The material was suggested to use as unique materials as pressure sensors in practicalapplications mainly for robots.q2001 Elsevier Science Ltd. All rights reserved.