Surface Modification of Carbon Fiber for the Enhancement of Mechanical Properties of Silicone Rubber/Carbon Fiber Composites

초록

Effects of incorporation of clay and carbon fiber (CF) into a room temperature vulcanized (RTV) silicone rubber, i.e., poly(dimethylsiloxane) (PDMS) terminated with hydroxyl groups, on its thermal stability and mechanical properties were explored through thermo-gravimetric analyses (TGA), universal test machine (UTM) and resistivity meter. A pristine CF was modified with strong acid to introduce hydroxyl and carboxyl groups on the surface. These functional groups on the surface of acid treated CF (acid-CF) were reacted with isocyanate groups of 3-isocyanatopropyltriethoxysiane compound to introduce the trialkoxy groups onto the acid-CF (i-CF). The isocyanate groups were converted to urethane bond (-NHCOO-) and amide bond (-CONH-) through the reaction with the functional groups of the acid-CF. The alkoxy groups may react with the hydroxyl groups of RTV and enhance the interfacial interaction between i-CF and the rubber. SEM image of the fractured RTV/CF composites showed clean CF surface. On the other hand, the surface ofi-CF appeared on the fractured surface of RTV/i-CF composites was covered with silicone rubber. Tensile strength was enhanced significantly with concomitant decrease in elongation at break. Addition of CF to the composites usually lowers the themalstability, due to the high thermal conductivity of CF. However, RTV/i-CF was more thennally stable than RTV/CF composites.