Surface and Mechanical Interfacial Properties of Oxyfluorinated Carbon Fibers-reinforced Composites

In this work, the effect of a direct oxyfluorination on surface and mechanical interfacial properties of PAN-based carbon fibers is investigated. The changes of surface functional groups and chemical composition of the oxyfluorinated carbon fibers are determined by FT-IR and XPS measurements, respectively. ILSS of the composites is also studied in terms of oxyfluorination conditions. As a result, FT-IR exhibits that the carboxyl/ester groups (C=O) at 1632 $cm^{-1} and hydroxyl group (O-H) at 3450 $cm^{-1} are observed in the oxyfluorinated carbon fibers. Especially, the oxyfluorinated carbon fibers have a higher O-H peak intensity than that of the fluorinated ones. XPS result also shows that the surface functional groups, including C-O, C=O, HO-C=O, and C-$F_x$ after oxyfluorination are formed on the carbon fiber surfaces, which are more efficient and reactive to undergo an interfacial reaction to matrix materials. Moreover, the formation of C-$F_x$ physical bonding of the carbon fibers with fluorine increases the surface polarity of the fibers, resulting in increasing ILSS of the composites. This is probably due to the improvement of interfacial adhesion between fibers and matrix resins.