Novel Boron Nitride Three-dimensional Porous Framework And Its Flame Retardant Bismaleimide Resin

High performance thermosetting resins with high temperature resistant have been used in a wide range of cutting-edge fields such as aerospace,electronic information,and new energy.However,the rapid development of modern technology asks for thermosetting resins with higher and more performances,especially,the exponential increase electronic material packaging density and calculation function significantly increase the power consumption,the resin for preparing thermal interface materials are required to have higher thermal conductivity and dimensional stability;meanwhile increased heat production also requires resins have better heat resistance and flame retardancy.Therefore,it is of great valuable to set up a simple and effective way to improve multiple properties of resins,including thermal conductivity,thermal stability and flame retardancy.Our research aims at developing higher performances resins with improved thermal conductivity and flame retardancy.Firstly,we prepared a boron nitride(BN)three-dimensional porous framework(sBN),meanwhile the continuity of the skeleton structure and the size of the pore size were determined by scanning electron microscopy and computed tomography.sBN was then used to frabricate new composite(sBN/BD)with allylic bisphenol A modified bismaleimide resin(BD).The effects of sBN on thermal stability,thermal conductivity and flame retardancy of composite were discussed.It is found that sBN not only can endow BD resin with reduced thermal expansion coefficient,significantly improved thermal conductivity,and increase char at 800 C,but also can extend the ignition time under continuous heating,reduce the peak heat release rate and smoke release of BD resin.sBN has played a role in suppressing smoke and charcoal,which is attributed to the higher thermal conductivity that can improve the thermal inertia of the material and make it difficult to be ignited.The generated heat can be quickly released to avoid excessive local burning,and the three-dimensional skeleton provides structural support for the carbon layer.However,it is also in the case of experimental small fire,compared with BN/BD composite,the sBN/BD is more difficult to self-extinguish with the same BN content,and has higher limiting oxygen index,that is attributed to the high thermal conductivity under low radiant heat,resulting in limited heat transfer to the interior of the material,and then causing continuous decomposition and repeated combustion inside the material.Secondly,in order to further improve flame retardancy of BD resin,alkyne-containing hyperbranched polysiloxane(THSi)was synthesized based on silicon-containing compounds for improving flame retardancy of polymer is an environmental and friend method,which was then used to prepare modified BD resin(TBD)with different THSi contents;moreover,TBD was vacuum cast into sBN to frabricate sBN/TBD composite.The flame retardancy and mechanism of TBD resins and sBN/TBD composites were discussed.Results show that sBN/TBD composites exhibit excellent flame retardancy,especially with better carbon formation,because the presence of silica oxygen chain promotes the formation of carbon at high temperatures and contributes to the formation of continuous anti-oxidation silicate protective layer.