Corrosion and Electrochemical Properties of EVA+Zn Electrodes from a Percolation Theory Perspective

Abstract

Composite materials and their physical properties have been widely studied because of their industrial applications. Among the composite materials, those consisting of an isolator phase filled with a conductive powder are of special interest in electrochemistry. Those materials combine the isolator and mechanical properties of the polymer phase with the conductive behaviour of the filler. With a large range of applications: corrosion prevention, shielding and electromagnetic interferences absorption, electrostatic unload, heat conduction, mechanical to electrical signal conversion or rechargeable batteries. The properties of this kind of materials are described by the Percolation Theory. When the filler content is increasing, the particles are forming individual clusters that are growing in the polymeric phase. At some characteristic value of the filler volume fraction, an infinite cluster is formed that crosses the whole of the material from one side to the other. This is the first percolation threshold (vc ) and will determinate important properties of the material, e.g. mechanical or electrichemical behaviour. The percolation threshold, also called critical volume fraction, varies from one material to another as a function of components densities and packing system and also of filler size and shape as well as on the procedure used for preparing the samples. Zinc powder is a typical filler of composite materials, with important technological applications on preventing corrosion systems and batteries [1,2]. EVA is an elastic polymeric material with a low melting point, used intensively in the industries of toys and footwear, because of the combination of their mechanical properties and easy processing. The EVA copolymer (ethylene-vinyl acetate) was filled with increasing amounts of powder zinc, from 10 to 75 %wt. Then, the electrical, thermal, mechanical and electrochemical properties of the mixtures of both materials or “product properties” are of promising usefulness. The aim of this work is to correlate the physical properties of the composite made with a different ratio of powder zinc dispersed within the polymeric matrix, with the objective of to characterize the electrochemic al and corrosion behaviour of these composite.1) J.R. Subiela; J. López; R. Balart; J.J. García-Jareño; F. Vicente. Electrical properties of EVA filled by zinc powder. Journal of Materials Science. 41 (2006) 6396 - 64022) J. Agrisuelas; J. García-Jareño; M. Piedras; C. Sanz; F.Vicente. Characterization of a New Polypropylene+Graphite+Zinc Ternary Composite. ECS Transactions 50 (2013). 71 - 80.