Abstract:Three kinds of flexibilizers, maleic anhydride-grafted ethylene-propylene-diene terpolymer (EPDM-g-MAH), maleic anhydride-grafted polyethylene-octene elastomer (POE-g-MAH) and maleic anhydride-grafted hydrogenated styrene-butadiene-styrene (SEBS-g-MAH), were used to toughen the polyamide 6/carbon fiber (PA6/CF) composites by melt-extrusion. The mechanical properties, morphology, crystalline structure, nonisothermal crystallization and subsequent melting behavior of PA6/CF composites were investigated. Incorporation of flexibilizers improves the mechanical properties of PA6/CF composites. Compared with PA6/CF composites, the tensile strength and impact strength of PA6/CF/EPDM increase by 7% and 16%, respectively. The scanning electron microscopy (SEM) indicates that modification with flexibilizers not only improves the toughness of the matrix resin but also enhances the interfacial adhesion between the carbon fiber and PA6 matrix. Nonisothermal crystallization behaviors and subsequent melting behaviors charactered by differential scanning calorimetry (DSC) show that the onset crystallization temperature (T_on), crystallization peak temperature (T_p), crystallization enthalpy (ΔH_c) and crystallinity (χ_c) of PA6 in PA6/CF composites increase after incorporation of flexibilizers and multiple melting behaviors owing to the existence of various crystalline forms in PA6. Simultaneously, a slight decrease in temperature of melting peak (T_m1) of PA6/CF composites toughened by flexibilizers is observed compared with PA6/CF. X-ray diffraction analysis (XRD) results show that the α-form crystalline structure is favorable in the composites when the PA6/CF composites is toughened by the flexibilizers, which demonstrates the multiple melting behaviors of PA6/CF composites.