Abstract:Three kinds of flexibilizers, maleic anhydride-grafted ethylene-propylene-diene terpolymer (EPDM-g-MAH), maleic anhydride-grafted ethylene-octene copolymer (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. Mechanical tests showed that incorporation of flexibilizers simultaneously improved the tensile strength and impact strength of PA6/CF composites. For PA6/CF/EPDM, the tensile strength and impact strength increased by 7% and 16%, respectively. However, PA6/CF/SEBS and PA6/CF/POE exhibited another trend that only one kind of mechanical properties was obviously improved. The scanning electron microscopy (SEM) indicated that modification with flexibilizers not only improved the toughness of the matrix resin but also enhanced the interfacial adhesion between the carbon fiber and PA6 matrix. It was observed from Nonisothermal crystallization behaviors and subsequent melting behaviors charactered by differential scanning calorimetry (DSC) that the onset crystallization temperature (Ton), crystallization peak temperature (Tp), crystallization enthalpy (ΔHc) and crystallinity (χc) of PA6/CF composites increased after incorporation of flexibilizers and multiple melting behaviors owing to the existence of various crystalline forms in nylon 6 were detected. Simultaneously, a slight decrease in temperature of melting peak (Tm1) of PA6/CF composites toughened by flexibilizers was observed compared with PA6/CF. The X-ray diffraction analysis (XRD) results showed that the α-form crystalline structure was favorable in the composites when the PA6/CF composites was added by the flexibilizers, which demonstrated the multiple melting behaviors of PA6/CF composites.