Effects of thickness and environmental factors on conductivity of composite coatings

To provide information for the manufacture and application of digital processing frequency selective surface (FSS), the properties of two conductive composite coatings consisting of silver flakes and resin matrix were contrastively investigated. With environmental accelerated test, attention was focused on the effects of environmental factors including temperature, humidity and corrosive atmosphere on their adhesion, microstructure and conductivity. Variation of their surface resistance was measured by bridge method, and their microstructure and pattern change of section and surface were observed before and after environmental test with SEM. The over-all properties of the polyurethane matrix composite coating is better than that of the epoxy resin matrix coating for the two coatings containing silver flakes. The effects of environmental factors on conductivity of the two coatings are obvious, though no appreciable influence on adhesion can be identified in experimental scope and parameter variation range. The negative effect of environmental factors on conductivity is attributed to the micro-damages occurred within the microstructures of the coatings.