Surface free energy study of virgin and recycled carbon fiber reinforced thermoplastic composites

This research paper reports the composite adhesion behavior of thermal treated recycled carbon fibers through contact angle and surface energy measurements and its results compared with virgin carbon fibers. Virgin and recycled carbon fiber composites in a hybrid Polypropylene/Polyamide12 (PP/PA12) matrix had its pure blend surface data measured from 50% up to 80% PA12 weight content compared with its selected 20%-80% PP/PA12 modified Maleic Anhydride Polypropylene (MAPP) and Poly[methylene(polyphenyl) isocyanate] (PMPPIC), individual material data values were also obtained. Surface energy results were obtained through Owens–Wendt-Rabel and Kaelble (OWRK) using water and diiodomethane for the contact angle measurements. The contact angle behavior versus time showed a linear pattern. Results showed that the overall surface energy decreased by the addition of MAPP and PMPPIC surface modifiers in pure PP/PA12 blends. The polar contribution improved by the addition of MAPP and PMPPIC for both PP/PA12 blend matrix and the final composite. The surface energy increased for the final carbon fibers composites compared with its matrices and the effect of the thermal treatment on the carbon fibers decreased the overall surface energy mostly in its dispersive component.