| Summary: | Surface properties of high-strength and high-modulus carbon fibers were studied by inverse gas chromatography. London components of the surface free energy were calculated from the increment per methylene group in the free energy of adsorption of n-alkanes at zero coverage. Values typical of low energy surfaces were obtained for both types of "as received" carbon fibers. Cleaning of the fibers at elevated temperatures under nitrogen caused a significant increase in the London component. This was attributed to the desorption of physically adsorbed species (CO$ sb2$, H$ sb2$O) that occupied the high energy sites on "as received" fibers. Similar results were obtained in the finite coverage region where London components were calculated from the spreading pressures of the hydrocarbons. Type II adsorption isotherms were measured for n-alkanes on carbon fibers. The fibers were pretreated by heating to various temperatures under nitrogen. The BET surface areas of the fibers increased with increasing pretreatment temperature, due to the presence of microporosity. From the spreading pressures of ethanol on carbon fibers, the polar interactions between ethanol and the fibers were estimated.
|
|---|
