Surface characterization and adhesion of carbon fibers to epoxy and polycarbonate

Surface characterization of the specially prepared Toray high-strength sample carbon fiber was undertaken with a view to evaluate and understand adhesion to polymer matrices. Surface chemical analysis by XPS, surface free energy determination from the dynamic contact angle, and microstructural characterization by STM was conducted and compared with before and after surface treatment of this fiber and with other PAN-based high-strength carbon fibers as well. It was found that the surface of Toray sample carbon fibers has higher O/C and N/C ratios than those of other PAN-based carbon fibers, such as the IM-7 and AS-4. The fiber surface free energy appears slightly lower than those of the IM7 and AS4. Adhesion of Toray Lab-carbon fibers measured by the single fiber fragmentation was determined to be in a similar level to AS-4 and IM-7 in various epoxy-amine thermoset systems and polycarbonate thermoplastic matrix.