Effect of Surface Treatment on the Conductivity of Polyurethane-Carbon Composites

The effect of plasma surface treatment on the mechanical and electrical properties was investigated by comparing untreated particulate carbon filler and treated carbon filler in a polyurethane matrix. For achieving this goal, samples of the composites were prepared with different percentages of carbon fillers (0 – 50 wt %) and conductivity measurements, dynamic mechanical analysis, mechanical properties, infrared spectroscopy and scanning electron microscopy were used to determine the effect of surface modification and concentration. The conductivity measurements showed that the percolation threshold was shifted to lower concentrations of carbon as compared to the predicted value especially for the untreated carbon filled samples. The untreated filled carbon composite samples exhibited this behavior due to precipitation of filler particles during the solvent casting of the film. In terms of mechanical properties (dynamic and transient), the effect of filler content and filler surface treatment was noted. FT-IR results indicates some degree of interaction between the treated filler surface and polyurethane. Scanning electron microscopy showed that composites based on a modified filler had better dispersion.