Synthesis And Characterization Of A High-temperature Bisphenyl Phthalonitril Resin

Phthalonitrile resins are an important class of high-performance resins which can be used in many fields, such as aerospace, shipbuilding, navigation and so on. But so far, most of the phthalonitrile resins have high melting points and short processing windows, thus these shortcomings limit the application of the material. In this paper, a new type of high-temperature preparation of phthalonitrile resin based on resorcinol can solve this problem very well.A new synthetic route of 4-nitrophthalonitrile as the intermediate of phthalonitrile resin was studied and optimized in this paper. It was prepared by phthalic anhydride as material through ammonification, nitrification, dehydration and other steps. The product has a purity of more than 99.5%. Then, by the starting materials 4-chloronitrobenzene and bisphenol S, the cross-linking agent 4,4’-bis(4-aminophenoxy) phenyl sulfone (p-BAPS) was synthesized via etherification and reducted by ion powder. The yield can up to 86.27%. Both of them were characterized by 1H-NMR.We mainly studied the synthesis and curing of phthalonitrile resin based on resorcinol. The oligomeric phthalonitrile was prepared in a two-step, one-pot procedure using an excess of resorcinol and 4,4’-difluorodiphenylmethanone as raw materials and terminated with 4-nitrophthalonitrile. The product was characterized by FTIR and !H-NMR. The monomer was thermally crosslinked in the presence of 4,4’-bis(4-aminophenoxy) diphenyl sulfone(p-BAPS) forming a void-free thermoset material. The curing property and thermal-oxidative stability of the prepolymer was investigated by DSC and TGA. The results showed that the melting point or softening point of the resins is about 60 ℃, and the beginning curing temperature is about 250 ℃. So the resins have a longer processing temperature window. And the resins retained about 95% weight at 350℃ and exhibited char yieldof 65% at 800℃. Thus the new phthalonitrile resin based on resorcinol has excellent thermal stability and thermal oxidation stability. And it can be used in many industries as thermosetting materials.