Preparation And Research Of Carbon Fiber Reinforced Thermoplastic Composites

Carbon-fiber (CF) reinforced polyamide-6(PA6) composites and CF reinforced polypropylene (PP) composites were prepared by melt-extrusion via continuous fiber fed during extruding. Their mechanical properties, non-isothermal crystallization, subsequent melting behavior, crystalline structure, spherulitic morphology and thermal stability were studied. Three kinds of toughener EVA-g-MAH, EPDM-g-MAH and SEBS-g-MAH were added to the PA6/CF and PP/CF composites to overcome the brittle shortcoming. The mechanical properties, crystalline and melting behavior, crystalline structure and morphology of PA6/toughener/CF, PP/toughener/CF composites were also discussed.The results showed that the incorporation of CF can improve the tensile modulus and strength by about60and50%respectively when the CF loading comes to20wt%, while their elongation at break were decreased. Scanning electron microscopy (SEM) observation on the fracture surfaces showed that fine dispersion of CF and strong interfacial adhesion between fibers and matrix. Dynamic mechanical analysis (DMA) results showed that the storage modulus of PA6/CF composites was improved with the addition of CF. Non-isothermal crystallization analysis showed that CF plays a role as nucleating agent in PA6matrix, and the a-form crystalline structure was favorable in the PA6/CF composites, as confirmed by the X-ray diffraction analysis(XRD) result. A trans-crystallization layer around CF could be observed by polarizing optical microscopy (POM), which proved the nucleation effect of carbon fiber surface on the crystallization of PA6. The thermal stability of PA6/CF composites was also enhanced.EVA-g-MAH, EPDM-g-MAH and SEBS-g-MAH showed good compatibility with PA6matrix. The PA6/Toughener blends owned higher enlongation at break about400%, and their impact strength were2,10and12times compare with that of pure PA6, while their tensile strength and tensile modulus were decreased. The impact strength of PA6/CF composites was also2～3times enhanced with the addition of tougheners, and the PA6/CF composites maintained comparable strength and modulus. PA6/EPDM/10owned the favorable mechanical properties, the tensile strength, modulus and impact strength were83.3MPa,2.63GPa and11.5J cm-2respectively. The nucleating ability and crystalline growing rates of PA6/CF composites were decreased with the addition of tougheners. PA/EVA/CF composites showed lower thermal stability, while EPDM-g-MAH enhanced the thermal stability of PA6/CF composites.The tensile modulus of PP/CF composites was improved with the incorporation, while the tensile strength, enlongation at break and impact strength were decreased. CF could play nucleating agent role in PP/CF composites and the nucleating effect can be obviously observed by POM. The P form crystalline was favourable in the PP/CF composites. EVA-g-MAH could not enhance the impact strength as its bad compatibility with PP matrix. The impact strength and enlongation of PP were improved with the addition of EPDM-g-MAH and SEBS-g-MAH. EPDM-g-MAH and SEBS-g-MAH highly enhanced the impact strength of PP/CF comopsites while rarely reduced the tensile modulus. The nucleating ability and crystalline growing rates of PPCF composites were also decreased with the addition of tougheners.