Reuse of carbon fiber waste to produce composites with polypropylene. The effect of styrene-(ethylene-butylene)-styrene grafted with maleic anhydride and ethylene-propylene-diene grafted with maleic anhydride copolymers

Carbon fiber (CF) is a difficult material to recycle, generating accumulation and environmental impacts when disposed of incorrectly. The practice of reuse is being encouraged, aiming to minimize socio-environmental impacts. The present research aimed to develop polypropylene (PP) composites with CF waste, using styrene-(ethylene-butylene)-styrene grafted with maleic anhydride (SEBS-MA) and ethylene-propylene-diene grafted with maleic anhydride (EPDM-MA), as compatibilizers. The composites were processed in a mixer and injection molded. The addition of the CF in the PP matrix did not hinder processability, as verified in torque rheometry. Significant increases were achieved in impact strength and elongation at break, especially in the PP/FC/SEBS-MA and PP/FC/EPDM-MA composites. Incorporating 15% EPDM-MA reduced the elastic modulus and tensile strength by 23% and 32%, while SEBS-MA by 13% and 23%, relative to PP, respectively, due to the increase in flexibility of the composites. When the PP/FC composites were compatibilized with SEBS-MA and EPDM-MA, there was a higher level of interaction among the phases, generating a higher wettability, as verified in the scanning electron microscopy. Such behavior was important to increase the crystallinity of the compatibilized composites. The composites thermal stability increased significantly, increasing in 40 degrees C, compared to pure PP. In general, the compatibilization with SEBS-MA was more effective, generating better properties. As a consequence, the heat deflection temperature of the composites remained the same as the level of pure PP, suggesting good structural stability. The results are valuable for the recycling area, since CF can be reused as a polymer additive to improve properties.