Coupling of carbon fibers to polycarbonate: surface chemistry and adhesion

Anodically oxidized carbon fibers (CF) were treated with four different coupling agents containing epoxy, anhydride, and isocyanate functionality. The bonding of the coupling agents to the fiber surface was determined by dissolution experiments, while the chemical composition of the surface was studied by diffuse reflectance infrared spectroscopy (DRIFT). Micro-composites were prepared from polycarbonate resins (PC) by compression molding. The effect of surface coverage, processing temperature and molecular weight on interfacial adhesion (IFSS) was determined by fragmentation. The amount of coupling agent bonded to oxidized carbon fiber depends on its chemical structure and on the reactions taking place on the fiber surface. Several of the coupling agents formed a polymer layer on the surface; its structure also influenced both coupling to the matrix and the strength of interaction. The organofunctional group of the coupling agents reacts with the chain-end hydroxyl groups of PC. The number of these is li...