Surface properties of oxyfluorinated PAN-based carbon fibers

In this study. the oxyfluorination of PAN-based carbon fibers was undertaken at room temperature using fluorine-oxygen mixtures, and the influence Of oxyfluorination on properties Such as wettability, Surface polarity, surface free energy, conductivity and tensile strength was investigated. As the oxyfluorination time increased at a total pressure of 5 kPa, both the fluorine/carbon and oxygen/carbon ratios increased, The contribution of semicovalent C-F bond to F1s spectra is considerably decreased kith increasing total pressure from 5 to 80 kPa, and at the same time, the contribution of covalent C-F bond is increased. As the total pressure of fluorine-oxygen mixtures increased, the contact an,,le of water significantly decreased and again increased to a similar value to that of as-received carbon fiber. A short oxyfluorination of carbon fibers considerably increased the wettability, that is, hydrophilicity. The electrical conductivity Of oxyfluorinated carbon fiber is larger than that of the as-received fiber. This is because the surface region of carbon fiber is fluorinated. An increase in the tensile strength of about 18% after oxyfluorination is observed. The increase in tensile strength Of oxyfluorinated carbon fibers can be understood as being due to a decrease in the diameter of the fiber, (C) 2002 Elsevier Science Ltd. All rights reserved.