Control of carbon fiber-polypyrrole interphases by aqueous electrochemical process

The morphology, surface free energy and chemical composition of carbon fibers containing polypyrrole interphases has been determined. The morphology of the polypyrrole coated fibers was measured by scanning electron microscopy (SEM). The surface microstructure of the interphases varied from smooth to rough and grainy. The electrolyte used in the formation of polypyrrole interphases has a remarkable influence on the morphology of the resulting coatings. The interphases formed by using toluene sulfonate were either smooth, microspheroidal, leafoidal or rough. The surface morphology of the polypyrrole interphases formed by using duodecyl sulfonate and sulfuric acid are predominantly smooth and rough, respectively. The wettability of the polypyrrole modified carbon fibers was estimated from the surface free energy of the fibers. Significant improvement of the surface free energy of the electrochemically modified fibers (60 < gamma less than or equal to 75 dynes cm(-1)) over the commercially surface oxidized fibers (gamma = 51 dynes cm(-1)), of about 40%, was obtained. Examination of the electrochemically formed polypyrrole interphases, by infrared spectrophotometry (IR) showed that the electrolytes were incorporated into the interphases. (C) 1998 Published by Elsevier Science Limited. All rights reserved.