EFFECT OF ELECTROLYTIC OXIDATION UPON THE SURFACE-CHEMISTRY OF TYPE-ACARBON-FIBERS .2. ANALYSIS OF DERIVATIZED SURFACE FUNCTIONALITIES BY XPS, AND TOF SIMS

Type AU carbon fibres were electrolytically oxidised in aqueous ammoni um bicarbonate and were analysed by time-of-flight secondary ion mass spectrometry (TOF SIMS) and, after derivatisation, by X-ray photoelect ron spectroscopy (XPS). The reaction of trifluoroacetic anhydride vapo ur with model polymers and carbon fibre surfaces were examined to enab le the surface hydroxyl group concentration [OH] to be determined. The conditions required for the stability of the label is discussed. The [OH] increased in a similar way to the overall oxygen concentration ov er the range of degree of fibre treatments (DFT) considered. Aqueous b arium labelling was also employed to determine the carboxylic acid con centration [COOH], which also followed a similar trend to that of the total oxygen signal. The relative O- and CN- ion signals in the SIMS s pectra from samples of differing DFT were also observed to increase in a similar way. These were followed using the normalised peak intensit y (NPI) parameter. Epichlorohydrin (ECH) was adsorbed onto the surface to determine the reactivity of the fibres of differing DFT to the epo xy functionality. A polymeric deposit was observed to result from the reaction with ECH, which complicated the analysis and prevented the us e of the chlorine concentration as a measure of ECH fixation. Instead, fibre nitrogen signal attenuation was used as a measure of the quanti ty of material adsorbed; this provided a qualitative assessment of the reactivity of the fibres to the epoxide. The level of ECH fixation in creased in line with that of the oxygen functionalities, and is consis tent with the assertion that these react with the epoxy group.