Graded epoxy-hard coal composites: Surface resistivity study

The goal set for this paper was to investigate the relationship between gradation of filler particles content in the epoxy matrix and the gradation of electric properties. In order to characterize the electric properties, the surface resistivity was selected, because it determined the surface ability to electrostatic charging, important in expected applications. In particular, the influence of conditions of centrifugal casting technique and microstructure parameters on electric resistivity was searched. Experimental models were elaborated that juxtapose the dependence of surface resistivity on the volumetric content of the filler, as well as casting rotational velocity. Investigations results confirmed that achieved graded composites were characterized by the reduced ability of electrostatic charging on one side and good insulating properties on the other side. Measured surface resistivities of order 10⁹-10¹¹ Ω allow to classify them as surfaces with reduced susceptibility to static electricity accumulation. These composites may be applied in areas where antistatic properties of the surface, with preservation of insulating properties in the remaining volume of the composite, are beneficial.