Preparation And Performance Study Of Carbon Fiber Water-based Sizing Agent Applied To Nylon Matrix

Carbon fiber reinforced composites are widely used because of their excellent properties such as high temperature resistance,corrosion resistance,fatigue resistance,high strength,light weight and good dimensional stability.Thermoplastic resin,as the matrix of composite resin,has the advantages of heating softening,cooling hardening,reusability,no chemical change during repeated heating,high heat resistance,forming in abrasive tools,cooling setting and high mechanical properties compared with thermosetting resin.Traditional carbon fiber reinforced composites mostly use thermosetting resins as matrix,and the corresponding research and development are mostly thermosetting sizing agents.For thermoplastic resin matrix,this kind of sizing agent is very different from its structure,resulting in the application of carbon fiber surface can not form a good interface with resin matrix.The mechanical properties of the composites are poor.In addition,most of the thermoplastic sizing agents studied at home and abroad are solvent sizing agents,which do great harm to the environment and human body.In order to improve the mechanical properties of thermoplastic composites to a greater extent,a water soluble thermoplastic carbon fiber sizing agent was designed and developed according to the characteristics of thermoplastic resin matrix.At the beginning of the experiment,water-soluble modified polycaprolactam sizing agent(TF03PPA)was prepared by directly selecting thermoplastic resin polycaprolactam 6(PA6)as raw material,introducing hydrophilic groups by adding phosphate ester(03P),and then ring-opening.The optimum reaction conditions were determined by water solubility and contact angle as follows:PA6 and 03P were used as raw materials,reaction time was 4 h,reaction temperature was 200 ℃,and feed ratio was 1:4.The structures of the products were analyzed by IR and NMR,and the interfacial properties and thermodynamic properties of the emulsion were analyzed.Through the test of emulsion surface tension and contact angle,the best performance is obtained when the emulsion concentration is 1 wt%.After sizing,the surface groups,morphology and monofilament strength of carbon fibers before and after modification were characterized by X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),and fiber elongation analyzer(XQ-1A).The results show that the content of oxygen-containing active groups on the surface of carbon fibers increases obviously,the roughness of carbon fibers decreases obviously,and the strength of carbon fibers increases obviously.In the end,the composites were prepared by using carbon fibers and carbon fibre cloth as reinforcing materials and thermoplastic polycaprolactam resin as matrix.The mechanical properties of the composites were characterized by universal material testing machine.Results The flexural strength of the modified carbon fiber/polycaprolactam resin composites increased by 35%and the interlaminar shear strength of the carbon fiber cloth/polycaprolactam resin composites increased by 46%.It shows that the interfacial properties and mechanical properties of the composites treated by the sizing agent have been improved obviously,which further proves the research in this paper.The sizing agent can be successfully applied to thermoplastic composites.