Synthesis And Properties Of High-performance Biphenyl Phthalonitrile Resin

As a kind of thermosetting resin with high-temperature resistance, the biphenyl phthalonitrile resin has an important application in many fields, such as electricconductors, adhesives and composite elements. However, the use of the biphenyl phthalonitrile resin is limited due to the high curing temperature and the small processing window, This paper is devoted to improve the processability with modifying the molecule structure and adding proper curing agent.Firstly, the 3,3’,4,4’-tetraamino diphenyl sulfone(TADS) was synthesized for use as a curing agent. The new synthesis process using 4,4’-diaminodiphenyl sulfone as starting materials had a high plurinatality, through the protection of acetic anhydride, the reaction of nitrations the reaction of alkaline hydrolysis as well as the reduction. The new synthesis process was time saving and easy to operate, the yield was high to 95.3%. Its structure was verified by 1H-NMR.Then, a kind of high temperature resistant biphenyl phthalonitrile resin using a new type of curing agent had been synthesized and characterized. The oligomeric monomers were prepared from reaction of an excess amount of resorcinol and 4,4’-difluorobenzophenone in the presence of weak bases in N-methylpyrrolidinone (NMP) as solvent, followed by end-capping with 4-nitrophthalonitrile. The product was characterized by IR and 1H-NMR. The oligomeric phthalonitrile monomers were cured by 3,3r,4,4’-tetraamino diphenyl sulfone(TADS). The product was characterized by thermogravimetric analyzer (TGA,heating rate 10℃/min)、 differential thermal analysis (DTA, heating rate 10℃/min) and differential scanning calorimeter (DSC, heating rate 10℃/min). It was found the biphenyl phthalonitrile resin showed high temperature stability after curing.The softening temperature was 70℃, the Curing temperature was 230℃ and the 5% weight loss temperature was 470℃ in N2.Finally, the curing mechanism under the influence of amine curing agent was studied by TGA、DSC and IR, The results showed that under the influence of amine curing agent, the high temperature resistant of the biphenyl phthalonitrile resin was better and the formation of triazine ring by cyclotrimerization of cyano group was detected by IR, At the same time, it did suggest that the structure of the curing agent played an important role in the curing reaction. the stronger the alkalinity was, the stronger the catalytic capacity was.