Preparation And Application Of Carbon Fiber Sizing Agent For Nylon 6

Carbon fiber reinforced nylon 6(CF/PA6)composites have the characteristics of low relative density,high specific strength and high specific modulus.They are widely used in aerospace,transportation,anticorrosive equipment,sports equipment and other fields.However,the smooth surface and chemical inert surface of CF/PA6 composites result in poor interfacial bonding performance,which limits the application range of CF/PA6 composites.Therefore,the mechanical properties of CF/PA6 composites were improved by coating the fiber surface with sizing agent containing active functional groups to enhance the interface strength between CF and PA6.In this paper,triethylenetetramine(TETA),bisphenol A diglycidyl ether(BADGE),butyl glycidyl ether(BGE)and other synthesis of hydrophilic,oleophilic epoxy resin emulsifier,the optimal synthesis process of emulsifier was studied.The sizing agent mixed with emulsifier and epoxy resin was prepared.The effects of sizing agent on the properties of CF and CF/PA6composites were discussed,and the mechanism of action was described.The main conclusions were as follows:(1)Epoxy conversion rate can measure the reaction degree of emulsifier synthesis.When the reaction temperature is T=50?,TETA concentration C_TETA=1.5mol/L,BADGE concentration C_TETA=2.5mol/L,mole ratio of reactants M_TETA:M_BADGE=1.5:1,the epoxy conversion rate reaches the maximum of 52.5%,which is the optimal synthesis process conditions of emulsifier.The mechanical stability and particle size distribution tests show that:The optimal mass ratio of emulsifier to the sizing agent prepared by E-44,M-4101H and MF-3102L was S1(1.5:1),S2(3.5:1),S3(3.3:1),and the average particle size was 0.360?m,0.272?m,0.264?m,respectively.According to the sizing agent particle size between 0.2-0.5?m standard.Thermogravimetric analysis(TG)showed that the initial decomposition temperatures of the prepared sizing agents S1,S2 and S3 were all higher than 300?,and they had good thermal stability.(2)The mass loss rates of S1CF,S2CF and S3CF obtained by modifying fibers with acetone ethanol solution washing sizing agent were small,which were 1.45%,6.70%and 1.64%,respectively.The surface morphology of S1CF,S2CF and S3CF showed no obvious change by scanning electron microscopy(SEM),which indicated that the interface adhesion between the sizing agent and the"CF-interface phase"of the fiber was good.The initial decomposition temperature of S1CF,S2CF and S3CF tested by TG was above 300?,and the thermal stability of S1CF was good.The surface roughness of S1CF,S2CF and S3CF were characterized by atomic force microscopy(AFM)as 75.3nm,83.5nm and 98.8nm,respectively,which were improved compared with that of RCF,and the maximum roughness of S3CF was 67.7%.The Raman test shows that the sizing agent is successfully applied to the fiber surface and fills the surface defect area,increasing the disorder and roughness.Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS)were used to analyze the presence of-O-,epoxy,-OH and other active groups on the surface of the fibers.The wettability of S1CF,S2CF and S3CF were 8.07%,6.61%and 8.69%higher than that of RCF,respectively.The tensile strength of monofilament was also improved and S3CF was the best.(3)The interfacial adhesion between CF and PA6 is an important factor affecting the mechanical properties of CF/PA6 composites.Dynamic thermomechanical properties(DMA)tests show that S1CF/PA6,S2CF/PA6,S3CF/PA6 compared with PA6,DCF(desizing)/PA6,RCF/PA6,S3CF/PA6 have higher energy storage modulus,higher glass transition temperature(T_g),lower loss modulus and lower loss factor(tan?).The interface adhesion of S1CF,S2CF and S3CF to PA6 was enhanced.The rheological behavior test showed that the complex viscosity(?*)of S1CF/PA6,S2CF/PA6 and S3CF/PA6 was higher than that of PA6,RCF/PA6and DCF/PA6,and the unwinding of PA6 molecular chain was more impeded,the thickening effect was obvious,and the interface bonding property of S3CF/PA6 was better.the mechanical properties were all better than those of PA6,DCF/PA6 and RCF/PA6,among which S3CF/PA6was the best.(4)Interfacial action mechanism of CF/PA6 composites:CF was modified by sizing agent,and active groups such as-O-,epoxy and-OH were introduced on the surface of the fibers to construct an interfacial phase that was not easy to fall off.The interfacial phase was bonded with PA6 through van der Waals force and molecular chain diffusion and winding.The epoxy group of the sipping agent reacts with the-NHCO-of PA6 to produce chemical bond,which further promotes the interfacial bonding between CF and PA6,forming a good"interfacial phase-PA6"interface.The interfacial phase plays a"bridge chain"role in the composite material,which enhances the interfacial adhesion of CF/PA6 composites and improves the mechanical properties of CF/PA6 composites.