Preparation,Flame Retardancy And Its Mechanism Of Flame Retardant Epoxy Resin Containing DOPO-Based Derivatives And Carbon Fiber Reinforced Epoxy Composites

Epoxy resin(EP)is a thermosetting polymer material with excellent adhesive properties,outstanding electrical insulation,and strong corrosion resistance.It is widely used in electronic and electrical appliances,aerospace,wind power blades,and transportation.The flammability of pure EP greatly increases the potential fire hazards when it is applied.Therefore,the flame retardant modification of EP has important practical significance.In view of the negative impact of the additive flame retardant on the properties of the matrix and the development requirements of halogen-free flame retardant,in this paper,DOPO,as a startaing material,is used to prepare a series of DOPO-based phosphonamidates and DOPO-based oligomers.It effectively solves flame retardant epoxy resin’s problems of high content,poor dispersion,low transparency and mechanical performance loss.The main research work is as follows:1.Based on the Atherton-Todd reaction mechanism,two DOPO-based phosphonamidates small molecules(DDM-DOPO and MPL-DOPO)are successfully synthesized,and the flame retardant epoxy resin with excellent overall performance was prepared.Because of the good dispersion of flame retardant,the flame retardant epoxy resin still maintains high transparency.The study found that DOPO-based phosphonamidates can significantly improve the flame retardant properties of epoxy resins.EP/2.5%DDM-DOPO composites can reach UL-94 V-0 test with 0.25%phosphorus content,and the LOI is as high as 30%.The test results show that DOPO-phosphoramide can reduce the gas product concentration,inhibit the combustion of gas products,and reduce the total heat release.2.Three kinds of DOPO-based oligomer flame retardants are prepared by molecular design,which are linear flexible chain DOPO-D230,linear rigid chain DOPO-OPA and hyperbranched structure DOPO-HB.They are used as reactive flame retardants to prepare intrinsic flame retardant epoxy.DOPO-D230 can increase the flexibility of the resin,improve the impact strength,and reach UL-94 V-0 level at 7.5%of the added amount;DOPO-OPA can improve the rigidity of the resin,increase the storage modulus at room temperature,and reach UL-94 V-0 level at 5%content;DOPO-HB can improve the rigidity of the resin,increase the storage modulus at room temperature,and reach the UL-94 V-0 level when the amount is 7.5%.3.The MPL-DOPO modified flame-retardant carbon fiber reinforced epoxy composites are successfully prepared by hand lay-up and vacuum molding techniques.The micro-morphology,mechanical properties,flame retardancy and flame retardant mechanism of the composites are studied.The cross-sectional image of the composite material shows that the epoxy resin completely infiltrated the carbon fiber.The limiting oxygen index of the unmodified carbon fiber reinforced epoxy composite is 24%,while the limiting oxygen index of the flame retardant carbon fiber reinforced epoxy composite is as high as 29%.The tensile properties and flexural properties of the composites slightly decrease,probably because the introduction of MPL-DOPO reduces the interfacial interaction between epoxy matrixs and carbon fibers.