Formation of Copper Sulfide Layers on the Surface of Polyethylene Films of Various Density by the Use of Polythionic Acids

The kinetic study of sulfur adsorption-diffusion processes from higher polythionic acid, H2S33O6, solution into polyethylene films of high, medium and low density showed that the sulfur concentration in polyethylene of various density and thickness increases with increasing temperature of the solution and the duration of treatment. Sulfur concentration in the film is related to the film density and thickness. An increase in the negative apparent adsorption heat of sulfur adsorption was observed with an increase of polyethylene films density. The estimated apparent sulfur diffusion coefficients in polyethylene increase with increasing temperature of the polythionic acid solution but decrease with growing crystallinity in the films. The concentration of sulfur in the film is limited by the stage of the acid decomposition, because the apparent activation energy of sulfur diffusion in polyethylene is nine to seventeen times lower than the energy needed for the polythionic acid decomposition. By treating polyethylene film sulfured inH2S33O6solution with copper( I-II) salt solution, copper sulfide (CuxS) layers are formed in the surface matrix of a polymer. The amount of copper in these layers is related to the density and thickness of the polyethylene film and the sulfuration conditions. The amount of copper increases with a decrease in the density of the polyethylene film and with an increase in the temperature ofH2S33O6 solution used and the duration of the treatment. Initially, dielectric polyethylene films after formation of copper sulfide layers in their surface matrix become electrical conductors. Samples of low density polyethylene with the layers of CuxS were the most conductive.