Preparation And Properties Of Flame Retardant Epoxy Resins Based On Phthalonitrile Derivatives

Epoxy resins(EP)are now used in a wide range of industrial,domestic,aerospace and aircraft manufacturing applications.However,epoxy resins are highly flammable and if they burn,they can ignite other objects around them,which can have serious consequences.Especially in the field of aerospace,where safety is of paramount importance,the study of flame retardant modification of epoxy resins is of great importance to improve the intrinsic safety of aircraft.In this paper,two high-temperature self-crosslinkable phosphorus-nitrogen synergistic flame retardants containing phthalonitrile groups and phosphorus elements were designed and synthesized for the flame retardant modification of epoxy resins.Through the characterization of their properties,the effect of cross-linking of flame retardants on the properties of epoxy resins and the flame retardant mechanism of flame retardants were investigated.The main studies in this paper are as follows:1.A mono-DOPO-monophthalonitrile flame retardant(APN-DOPO),a flame retardant intermediate widely used in the field of flame retardancy,was selected as the main raw material with 3-aminophenoxyphthalonitrile(3-APN),and was added to the epoxy resin matrix to prepare a flame retardant cross-linked(The results of the flame retardant tests show that at 5%addition,5AD/EP has already reached UL-94 V-0 level with an ultimate oxygen index of 29.6%,and at the same addition,cl-5AD/EP has been able to achieve an ultimate oxygen index of 40.8%as well as a higher performance in vertical combustion.The above experimental results and other performance test results show that the cross-linking of flame retardants can effectively improve the flame retardant properties of epoxy resins and maintain other properties,while the characterization results of the flame retardant mechanism show that the cross-linking of flame retardants can improve the flame retardant effect in both the gas and condensed phases.2.Also using DOPO and 3-APN as raw materials,the double DOPO-bis-phthalonitrile flame retardant(PBD)was redesigned and synthesized.On the basis of the demonstration that the flame retardant cross-linking can effectively improve the flame retardant performance of epoxy resin,a sample strip of PBD cross-linked flame retardant epoxy resin was prepared,and the improvement of the flame retardant structure brought further improvement of the flame retardant performance.The improved structure of the flame retardant brings further improvements in flame retardancy.Other properties of the material are also maintained and the cross-linking of the PBD has been shown to produce a denser and stronger carbon residue by burning the epoxy resin,thus further improving the flame retardant properties.