Preparation And Application Of Polyaryl Ether Ketone Sizing Agent For Carbon Fiber Surface Modification

In this paper,the surface of carbon fiber(CF)was modified by sizing agent to improve the infiltration and adhesion between CF and PEEK resin,thus the interfacial properties of CF/PEEK composites was enhanced.This study provides an aqueous PEEK-NH₂ sizing agent and its preparation method.According to the principle of“like-dissolves-like”,a series of soluble aminated polyether-ether-ketone(PEEK-NH₂)were synthesized from the perspective of molecular design as the main resin to prepare the sizing agent,which effectively improved the compatibility between sizing agent and PEEK matrix resin.The introduction of benzene ring into PEEK-NH₂ polymer could reduce the regularity of its molecular chain to endow it with excellent comprehensive properties of both high temperature resistance and solubility,which solved the difficulty that the original PEEK resin can not be made into sizing agent because of its insolubility in general organic solvents.At the same time,-NH₂ could form chemical interaction with ketone bond in PEEK resin to form imine bond to further improve the interfacial adhesion between carbon fiber and PEEK resin.TGA and DSC results showed that PEEK-NH₂ resin exhibit excellent thermal properties.The initial decomposition temperature(T_5%)was above450?,higher than the processing temperature of CF/PEEK composites.Besides,the Tg of PEEK-NH₂ increased by 30.9?compared with PEEK.Novel water-based sizing agents with PEEK-NH₂resin as major materials were then prepared by emulsion/solvent evaporation method.The influence of emulsifier type and concentration,resin concentration,ultrasonic power and time on the emulsifying effect during the preparation process was systematically studied.The optimal preparation process parameters of sizing agent were determined.Thereinto,ultrasonic power was 400 W and shear time was 5 min.Besides,cetyltrimethylammonium Bromide(CTAB)with the concentration of 0.5 wt%was seleceted as the emulsifier,and the concentration of PEEK-NH₂ resin was 0.5 wt%.The sizing agents with outstanding kinetic stability was successfully prepared,the particle diameters of its ranging from 54.3 to 73.6 nm,able to store more than three-month.SEM was used to characterize the surface morphology of CF before and after sizing.The results showed that the PEEK-NH₂ sizing agent had good film-forming properties on the surface of CF,and the contact angle of modified CF decreased significantly,indicating that the sizing agent could greatly improve the wettability of the CF surface.CF/PEEK composites were prepared by hot pressing technique,and the interfacial properties of its composites were tested.According to the results,PEEK–NH₂–35 presented the most effective reinforcing effect,the interlaminar shear strength and flexural strength were increased by 43.1%and 62.2%,as compared to un-sized CF composites.Moreover,the interfacial strengthening mechanisms of sizing agent was investigated.The improved interfacial adhesion benefits from PEEK-NH₂ which performs as effective stress transfer bridge at the interface.