Study On The Interfacial Compatibility Of A Novel Phthalonitriles And Carbon Fiber

Phthalonitrile,as a new type of high temperature resistant resin,is widely used in aerospace industry and other fields,which led to an emphasis on the research and development of new phthalonitriles among the applications of high-performance composite materials in recent years.In this paper,the synthetic process and the compatibility with the carbon fiber interface of a novel phthalonitrile developed by the National University of Defense and Technology are studied.Specific research work is as follows:Synthesis and post-treatment of 4-(2-hydroxyphenoxy)phthalicnitrile,one of the new phthalonitrile monomers,using catechol and 4-nitrophthalonitrile as raw materials Work was conducted to investigate the post-treatment work of 4-(4-aminophenoxy)phthalic nitrile,one of the resin monomers.The results of the study show that the nucleophilic substitution reaction of catechol and 4-nitrophthalonitrile in DMF under the presence of K2CO3 and N2 protects the synthesis of 4-(2-hydroxyphenoxy)phthalic nitrile.Nitrile.The optimal synthesis conditions were as follows:catechol:anhydrous potassium carbonate:4-nitrophthalonitrile = 2:1:1,reaction temperature 80°C,solid-liquid ratio 0.222 g/mL,and final yield reached 87.64%.The crude product was able to separate the impurities and the target initially in a 1 mol/L NaOH aqueous solution,and then washed with hot water to obtain the final product with a yield of 45%,the production efficiency was greatly improved.The post-treatment process of 4-(4-aminophenoxy)phthalic nitrile was replaced by silica gel and activated carbon adsorption in place of the original silica gel column chromatography.The yield was 87%,and the post-treatment efficiency was also greatly improved.The interfacial wettability of the new phthalonitrile and T700SC carbon fiber was characterized.The research results show that the dynamic contact angle between phthalonitrile and carbon fiber decreases with increasing temperature in the range of 110?-130?.That is,wetting performance increases with increasing temperature,phthalonitrile and unsized carbon fiber at 130? has the smallest contact angle of 92.54°.Chemical treatment,chemical grafting method,polymer coating method and coupling agent method were used to treat the surface of T700SC carbon fiber.The effects of different surface treatments on the interfacial compatibility of carbon fiber and phthalonitrile were studied.At 130?,chemical oxidation,chemical grafting,and polymer coatings all improve the wetting properties of phthalonitriles and carbon fibers.Characterize the interfacial strength of the phthalonitrile and the T700SC carbon fiber.The results show that the interfacial shear strength of phthalonitrile and unsized carbon fiber increases with the increase of curing temperature in the curing temperature range of 320?-380?,and the interfacial shear strength of phthalonitrile and carbon fiber at 380?.It reaches 79.49MPa at the curing temperature of 380?,the interfacial shear strength of the solvent-coated carbon fiber and phthalonitrile of the phthalonitrile reaches 86.98MPa,and the interfacial shear strength of the sizing-containing carbon fiber and the phthalonitrile reaches 83.93MPa.Respectively,was 9.42%and 5.60%higher than the interface shear strength of unsized carbon fiber and phthalonitrile.