Preparation And Properties Of Carbon Fiber Sizing Agent Applied To Polyamide Matrix

Carbon Fiber(CF)has excellent high strength and high model property,but it can not be used alone due to brittleness of its body.It is usually applied in composite materials to play a filling and strengthening role.Because the surface of carbon fiber is inert and incompatible with most materials,it can not show its excellent performance.Therefore,it is necessary to modify CF to optimize the interfacial properties of the composites.In industry,sizing agent is usually used to modify the surface of CF.The method has low cost and simple process.However,for different composite materials,the interface characteristics are different,and specific sizing agent needs to be prepared.In this paper,thermoplastic polyamide 6(PA6)was selected as the substrate,and different molecular weight amide oligomer(LPA6)was designed to react with epoxy resin(E44)to prepare different sizing agents.The surface of carbon fiber was further modified by sizing,and the modified carbon fiber and PA6 were blended and modified to prepare different PA6/CF composites.The characterization of slurry,slurry solidified material,modified carbon fiber and carbon fiber composite was carried out.Modified silica(Si O₂)with different contents was mixed into the slurry,and the best slurry was modified.The effects of modified silica on the properties of slurry and composite materials were studied.Firstly,caprolactam was used for ring-opening reaction under water condition,then polycondensation reaction was carried out under high temperature condition,and adipic acid was used to seal the end to obtain amide oligomers with different molecular weights,and then reacted with epoxy resin to obtain epoxy sizing agents curing with different molecular weights.The results of hydrogen NMR and Fourier transform infrared spectroscopy showed that the specific molecular structure was successfully synthesized.At the same time,the size distribution and thermal stability of the slurry were tested,which showed that the synthesized product could withstand 300?and could be used in the processing of PA6/CF composites.Second,using different sizing agent on the carbon fiber surface sizing,through different sizing conditions,optimized the sizing process parameters,and then USES the Fourier infrared spectrum,X-ray photoelectron spectroscopy,methods of dynamic contact Angle and the amount of hair silk,analyzes the characteristics of CF surface,change,using scanning electron microscopy and scanning probe microscope to observe the different surface morphology of carbon fiber.The results show that the polar bond content on CF surface increases,and the nitrogen content in CF surface increases obviously.The polarity force on CF surface increases significantly when the sizing agent is successfully coated on the surface.From the surface morphology,it is found that the coating effect of low molecular weight sizing agent is more uniform.Secondly,by preparing different PA6/CF composites(PA6-OCF,PA6-OCF-01,PA6-OCF-02,PA6-OCF-03),the thermal properties,mechanical properties and microstructure of PA6/CF composites were studied.The results show that the tensile,bending,notched impact and non-notched impact strength of the composites(PA6-OCF-01)coated with low molecular size slurry with smaller particle size and more uniform dispersion are the highest,and the tensile,bending,notched impact and non-notched impact strength are increased by 17.6%,21.7%,16%and 21%,respectively,compared with that of unsized carbon fiber composites(PA6-OCF).Finally,the sizing agent was further modified by modifying silica.Results show that the addition of silica,significantly improves the sizing of carbon fiber surface polarity,surface energy and dispersion,coating is uniform,with 10%of the modified Si O₂,the compound material mechanics performance best,less starch composites,the tensile,bending,notched impact and notched impact strength increased by 27.3%,36%,19%and 30%respectively.