Synthesis And Properties Of Reactive Flame Retardant Curing Agent For Epoxy Resin

Epoxy resin is widely used in various fields of national economy because of its excellent insulation,corrosion resistance,adhesion and mechanical properties,especially in high-tech fields such as electronic and electrical components packaging,aerospace and so on.Because of the low oxygen index of untreated epoxy resin,it belongs to flammable material.Because of its flammability,its application in many fields is greatly limited.Therefore,flame retardant epoxy resin has become a very important topic.The traditional flame retardant of epoxy resin is the introduction of inorganic flame retardant such as phosphorus,magnesium hydroxide,aluminum hydroxide,etc.Although this additive flame retardant has good flame retardant effect,it greatly reduces the mechanical properties of epoxy resin.At present,halogen and antimony compound flame retardants are widely used in epoxy resin flame retardants.Although this kind of flame retardant has good flame retardant effect,it will produce a large number of toxic substances when it decomposes at high temperature,which is easy to cause secondary injury of fire escape personnel and environmental protection problems.Compared with halogenated flame retardants,phosphorus nitrogen compound flame retardants are expected to be the best substitute for halogenated flame retardants due to their high efficiency,non-toxic and stable mechanical properties.Therefore,it is of great practical significance to develop phosphorus nitrogen compound flame retardants.In this paper,five kinds of p-n intumescent flame retardant curing agents were synthesized by using pentaerythritol diphosphate diphosphate chloride(SPDPC)and Phenylphosphonic dichloride(PPDC)as two different intermediates.The effects of different phosphorus and nitrogen ratios on the flame retardancy and mechanical properties of epoxy resin were investigated.Firstly,the phosphorous spiro intermediate spdpc was synthesized from pentaerythritol(PER)and phosphorus oxychloride(POCl₃).Then,SPDPC was used as intermediate to react with 1,3-p-phenylenediamine(PXDA),isoflurone diamine(IPDA)and1,2-cyclohexanediam-ine(DACH)to prepare three new phosphorus nitrogen composite flame retardants.Their structures were characterized by IR,MS,NMR and TG And DTG were used to analyze its thermal performance.A series of flame retardant epoxy resin composites were prepared with three new phosphorus nitrogen composite flame retardant curing agents.The thermal properties,flame retardant properties,cone calorimetry(CCT)and mechanical properties of the composites were analyzed.The flame retardancy and mechanical properties of the intermediate SPDPC and three kinds of amines synthesized phosphorus nitrogen flame retardant curing agent in epoxy resin composites were tested.It was found that spdpc had excellent performance,good flame retardant effect and excellent flame retardant effect.At the same time,the ring structure of SPDPC had certain flexibility.The prepared flame retardant had the opposite ring in the subsequent epoxy resin composites The effect of oxygen resin on mechanical properties is relatively small.Two novel flame retardant curing agents,phenylphosphony 1,2-cyclohexanediamine(PPDAC)and phenylphosphony 1,3-propanediamine(PPDPA),were synthesized with1,2-cyclohexanediamine(DACH)and 1,3-propanediamine(DPAN)using phenylphosphonoyl dichloride(PPDC)as phosphorus containing intermediate.Their structures were characterized by IR,MS and NMR,and their thermal properties were analyzed by TG and DTG.A series of flame retardant composites were prepared with PPDAC,PPDPA and E-51 epoxy resin respectively.The thermal properties,flame retardancy and mechanical properties of the composites were analyzed.The flame retardant mechanism was studied by the morphology of residual carbon after combustion.The test results show that the two flame retardants have good flame retardant effect,but the flame retardant effect of SPDPC intermediate is better than that of PPDC.