Surface modification of oxidized carbon fibers by grafting bis(triethoxysilylpropyl) tetrasulfide (TESPT) and rubber sizing agent : Application to short carbon fibers/SBR composites

Bis(triethoxysilylpropyl) tetrasulfide (TESPT) with ethoxysilyl and tetrasulfide groups were grafted successfully on the oxidized short carbon fibers (CF) surface in order to create a strong continuous network between short CF and styrene butadiene rubber (SBR). The Hummer's method has been used for initial surface modification of short CF by solution oxidation (CF-OH) to establish hydroxyl groups required for the grafting process. Furthermore, a novel “rubber sizing agent” on the surface of short CF was applied by solution of SBR for the first time (CF-OH-g-TESPT-SBR). The surface of the modified short CF analyzed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM) micrographs to confirm the oxidation, grafting of TESPT and rubber sizing agent onto the CF surface. Then the SBR reinforced with different loading of modified short CF composites were compounded in a two-roll mill. The highest value of electrical conductivity and thermal properties was achieved at 5 phr modified short CF in SBR composite. Tear strength was increased to 24.5% in the transverse direction of the modified short CF. This has agreement with the results of surface morphology of fracture and weight loss of the composites by SEM and TGA, respectively.