Study On Preparation And Properties Of High Performance Thermoplastic Resin Sizing Agent

Carbon fiber reinforced high performance thermoplastic resin matrix composites(CFRTP)are widely used in aerospace,rail transportation and other fields due to their unique advantages,such as high toughness,low cost,rapid prototyping,secondary processing and recyclability,compared with traditional thermosetting composites.As an ideal matrix for preparing thermoplastic composites,naphthalene biphenyl copolymerized ethersulfone(PPBES)has excellent heat resistance and good solubility and processing fluidity.However,PPBES has poor compatibility with the mainstream epoxy resin sizing agent,and the molding temperature does not match,resulting in low interface bond strength and poor mechanical properties of CF/PPBES composite materials.Therefore,there is an urgent need to develop a thermoplastic sizing agent suitable for CF/PPBES composite materials.In this paper,based on the principle of"similar compatibility",two types of PPBES-based thermoplastic sizing agents,water-dispersed emulsion and solution,were prepared with PPBES as the main slurry.The optimal process conditions for the preparation of emulsion sizing agent by phase-shifting emulsification were determined as follows:When octyltrimethylammonium chloride(STAC)was used as emulsifier and the content of emulsifier was 18.75%,the shear rate was 11000 r/min,the emulsification temperature was room temperature,and the average molecular weight of the main resin was 5000 g/mol,the emulsion sizing agent had the best stability.The solution sizing agent used a mixture of chloroform:NMP=2:8 as the solvent for sizing agent,and the solvent was removed by the stage heating method.The content of O and N elements on the surface of desized carbon fiber increased after emulsion sizing,and the surface energy increased from 37.95 mJ/m~2 to 49.02 mJ/m~2.SEM observation showed that the optimum concentration of sizing agent was 1.0%.The bending strength and interlaminar shear strength of resizing CF/PPBES increased by 13.0%and 9.4%,respectively.The DMA results showed that the glass transition temperature of the composite increased by 6~oC,and the storage modulus increased by 45.7%.After solution sizing,the content of O and N elements on the surface of desized carbon fiber also increased,and the surface energy increased from 37.95 mJ/m~2 to 47.36 mJ/m~2.The bending strength and interlaminar shear strength of CF/PPBES increased by 12.0%and 11.1%,respectively.through observing the surface morphology by SEM and mechanical performance test results,the optimal concentration of sizing agent was 1.5%.The DMA results showed that the glass transition temperature of the composite increased by 9~oC,and the storage modulus increased by 33.0%.Through observing morphologies of fracture surface after flexual strength and interlaminar shear strength tests,both sizing agents effectively increased the interfacial bond strength of the composite.