Preparation And Properties Of High Performance Phthalonitrile Resin/boron Nitride Composites

Phthalonitrile resin is a kind of highly crosslinked thermosetting polymers,which is polymerized by nitrile interaction with catalysts and monomers containing a phthalonitrile compound.Phthalonitrile resin is a new type of high performance polymer materials with high temperature resistance,outstanding thermal decomposition temperature and glass transition temperature,excellent heat and oxygen stability,mechanical properties,flame retardant performance and low water imbibition,and superior comprehensive performance.Boron nitride（BN）has high thermal conductivity,high heat resistance,high insulation and low expansion coefficient,which can be used as a good thermal conductive filler to improve the thermal conductivity of the polymer.In this paper,phthalonitrile resins with different structures and with autocatalytic amino groups were prepared.The effects of different position isomers and chemical structures of the monomers on processing performance,thermal stability,dynamic mechanical properties,catalytic efficiency,thermal conductivity and so on were studied.Thermal conductive composites of phthalonitrile resin/hexagonal BN were prepared.The influence laws of doping methods,doping amounts,shapes,sizes and surface modifications of BN on the processing performance,thermal stability,dynamic mechanical properties,thermal properties of composites were studied.Thermal conductivity coefficients of the composites were predicted by a variety of thermal conductive models.The main results are as follows:Three monomers containing benzodiazepines isomers were synthesized,and three phthalonitrile resins were prepared with 4,4’-diamino-diphenyl ether（ODA）as catalyst by procuring and postcured processes.The processing window,thermal stability,energy storage modulus and glass transition temperature of phthalonitrile resins of the three benzodiazepine isomers were compared.Results show that the comprehensive performance of o-benzene and m-benzenetype phthalonitrile resins is better than that of p-benzene type phthalonitrile resin,with properties of m-benzene type phthalonitrile resin optimal.Three compounds containing amino isomers were synthesized.Results suggest the catalytic behavior,processing window,thermal stability and dynamic mechanical properties of phthalonitrile resins with different doping contents of the para amino compounds,as well as those of different amino isomers compounds with the same doping amount.The results show that the comprehensive performance of phthalonitrile resins is best when the content of para amino compounds is 10wt.%,and the catalytic efficiency of para amino compounds is better than that of ortho amino compounds and meta amino compounds.Curing kinetics of the three amino isomers compounds and thermal degradation kinetics of the three phthalonitrile resins were studied.Results show that the catalytic activity of para amino compounds is optimal,and thermal decomposition activation energy of phthalonitrile resins with para amino compounds is the highest.The structures of biphenyl and bisphenol A were introduced into the monomers to synthesize monomers and phthalonitrile resins with biphenyl and bisphenol A structures were prepared with 4-NH₂-CN as catalyst.The processing window,thermal stability,dynamic mechanical properties and thermal conductivity of the three phthalonitrile resins were analyzed and compared.Results show that the processing performance of bisphenol A type phthalonitrile resins is optimal but the thermal stability,mechanical properties and thermal performance are the worst.The processing performance of biphenyl type phthalonitrile resins is the worst but thermal stability,mechanical properties and thermal conductivity are optimal.The m-benzenetype phthalonitrile resin has the best comprehensive performance.The proportion of triazine ring and triazine ring structure and the crystallinity of three phthalonitrile resins were analyzed and calculated by FT-IR and XRD.The results show that the molecular structure and crystallinity of phthalonitrile resins take an active influence on the thermal conductivity.The boron nitride sheet was dispersed in phthalonitrile resin matrix by methods of ontology cladding,mechanical mixing and water mixing,respectively.Results indicate that the sheet boron nitride can be well dispersed in the resin matrix by the method of ontology cladding.Two kinds of micron boron nitride sheet with particle sizes of（TW05BN and TW12BN）were selected to mix with phthalonitrile resins,and the corresponding phthalonitrile resin/BN composites were prepared.With the increase of amounts of boron nitride,the processing performance and filler dispersion decline,and thermal stability,mechanical properties and thermal performance rise.A variety of heat conduction models were used to predict the thermal conductivity of composites containing boron nitride with different particle sizes.Results of series model,Bruggeman model,Cheng-Vachon model and Hatta-Taya model are basically in line with the experimental data and the error ranges of the predicted thermal conductivities and experimental values are small.Through in situ deposition technique,BN/Al₂O₃ composite particles were prepared in two steps,and the preparation process conditions of BN/Al₂O₃ were studied.The unmodified and modified spherical nitride boron and phthalonitrile resins were mixed by a method of ontology cladding,and phthalonitrile resin/spherical nitride boron composites were prepared.With the amount increase of boron nitride,the processing performance,thermal stability and filler dispersion of composites decline,and mechanical properties and thermal performance rise.Thermal conductivity of two phase composites were predicted by a variety of thermal conductivity models,in which series model,Maxwell-Eucken model,Bruggeman model and Cheng-Vachon model could predict the thermal conductivity values in the experimental error range.Three-phase Agari model were used to predict the crystallization and thermal conductivity chain free factor of phthalonitrile resins/BN/Al₂O₃ composites.The results show that Al₂O₃ has the higher probability than BN to form the thermal conductivity chain,and BN and Al₂O₃ cause a decline in the crystallinity of phthalonitrile resin matrix.