Surface characterization of plasma-modified carbon fiber: Correlation between surface chemistry and morphology of the single strand

To prepare cohesive polymeric composite, plasma-modified carbon fibers (CF) were prepared. Among the different strategies to modify the CF surface, the plasma functionalization, a promising eco-process, induces both chemical and topographic modifications of the CF surface. Surface characterization of such material composed of several thousands of single strands requires specific analyzes well suited for both single strand or fiber samples. The wettability measurement of modified strand or fiber thanks to the simple contact angle measure is unobvious. Therefore, their wetting profiles in different liquid probes were captured to determine the exact surface free energy of plasma-modified CF with a remarkable precision. Furthermore, the obtained results were correlated with more conventional chemical and morphological surface analyses. The increase of surface free energy was linked to the appearance of acidic (COO) and ether (C-O-C) groups on plasma-oxidized CF. However, the O-2 plasma-treatment showed a limited improvement of CF surface properties, due to their excessive oxidation altering their crystalline properties.