Filmes piezo-resistivos de resina epoxídrica com partículas de negro-de-fumo

Abstract

Materials that change its resistance after suffer deformation have various types of applications as sensors. Between the materials that may be used in this purpose, there are those called conducting particles immerse in isolating polymeric matrix. Carbon black (CB) particles has high electrical conductivity, allowing them be included in resin epoxy (EPX) matrix making it an electrical conductor composite, even in low volumetric fractions of CB. The goal of this work is the craft of a conducting polymeric film that has piezoresistive behavior to be utilized as strain sensors. As substrate polypropylene slabs when fixed in rigid elements showed higher efficiency to this end. Another relevant aspect to the film elaboration was the search for a solvent to lower the viscosity of the EPX to ease the homogeneity of the composite. Acetone showed a good potential as solvent of this composite. Also the relations between monomer, catalyst and acetone was changed, and was noted that independent of the quantities of the solvent, it remains the ability of making films. By current-voltage measurements in two ways, by the surface and transversal, was found the minimum quantity of CB needed to make the film conductor (percolation threshold) is between 3 and 4% in volume. Stress-strain test by traction, made possible establish some mechanical properties of the composites, as the strain in the highest stress between 2,5%, with small fluctuations in this value by the amount of CB, making also possible find the elastic/plastic threshold, also the stress in ruptures near 30 MPa, showing the maximum allowed stress in the material. The sensor showed efficient for small strain and in special, when used fixed with substrate.