TRIBOLOGICAL PROPERTIES OF ELECTROACTIVE POLYMERIC THIN-FILM BEARINGS

We report a preliminary study of the tribological properties of electr oactive polymeric films. A total of 120 polymer films - either poly(py rrole), poly(N-methylpyrrole), poly(5-carboxyindole) or poly(aniline) - were electrochemically deposited from an electrolyte solution contai ning the monomer onto a gold film that bad, in turn, been evaporated o n to the convex face of polished glass substrates. These were rubbed a gainst a fused-silica disc, of surface roughness 10 nm R(a), at a surf ace speed of 7.7 mm s-1. Theoretical and experimental analysis of thin film bearings shows that the frictional properties are strongly depen dent upon the load, film thickness and bearing geometry, and therefore a constant applied normal force of 2 N is used throughout the experim ents. Steady state and transient frictional forces were monitored by a sensitive pin-on-disc friction testing apparatus with a force resolut ion of 5 mN, which is described. Because the films were usually less t han lO mum thick, the time required for the tribological characteristi cs of the substrate to dominate was used as a monitor of the wear of t he films. It is shown that friction coefficients ranging from 0.70 to less than 0.02 can be achieved, and the value almost continuously cont rolled through choice of electrolyte solution and deposition parameter s. It is also observed that the more durable materials generally showe d higher frictional coefficients, which is characteristic of shear-rel ated wear at the interface.