THERMAL AND ELECTRICAL STABILITY OF POLYPYRROLE AT ELEVATED-TEMPERATURES

The two sides of electrochemically produced polypyrrole p-toluene sulfonate film react differently in kinetic studies of thermal aging. Oxidation, diffusion and temperature determine the rate of loss of conductivity in the anisotropic film. Some samples were protected on one side, by adhesive polymide tape, while the conductivity was monitored during ageing at temperatures between 70 and 150-degrees-C. Below 90-degrees-C the rate of decay depends on which side of the film is exposed to the air; above 90-degrees-C the rate of decay is the same irrespective of which side is covered; and above 120-degrees-C the initial rate of decay depends on the exposed surface area of the film. Thermal analysis suggests that when these polypyrrole films are plasticized by moisture they have a glass transition in the range 65-95-degrees-C and that, when freshly prepared, they undergo further reaction when heated above room temperature.