A Study On Synergistic Flame Retardant Epoxy Resin For Vacuum Assisted Resin Infusion Carbon Fiber Composites

The most common process to manufacture advanced composites is the costly autoclave.One of the out-of-autoclave alternatives is the low-cost vacuum assisted resin infusion(VARI)which produces quality parts with less pollution.Carbon fiber reinforced polymer(CFRP)is a high performance product,which has light weight,high strength,high temperature resistance,corrosion resistance and excellent mechanical properties.It is widely used in many industrial fields.Epoxy resins are a widely used composite matrix resin,but their high flammability limits their use as interior composite parts for vehicles.The usual flame retardant for epoxy involves halogen,which is effective but has high smoke toxicity.As a result,halogen-free flame retardant epoxy resin systems become dominant.Traditionally halogen flame retardant is the main flame retardant modification of epoxy resin,but the acid and dioxins produced by halogen flame retardant combustion have great toxicity,so halogen-free flame retardant epoxy resin has gradually become mainstream.In this paper,explored the effects of different halogen-free flame retardants on the viscosity,flame retardant efficiency,and mechanical properties of epoxy resins.It was found that the halogen-free flame retardants on market cannot effectively meet the requirements of infusing resins.Therefore,the flame-retardant modification of the body resin has become a new option.Next,used benzoxazine supplemented with dimethyl methyl phosphonate(DMMP)flame retardant intrinsically flame-retardant modified epoxy resin.Firstly,the effects of benzoxazine and DMMP on the performance of various aspects of the resin system were explored;Then the effects of different curing processes on the performance of the cured resin product were explored;Secondly,neopentyl glycol glycidyl ether was used adjusts the viscosity,and on the other hand explored the effect of the addition of the diluent on the flame retardant performance and thermomechanical properties;Then explored the effect of different benzoxazines on epoxy resin;Finally used VARI explored the mechanical properties and flame retardancy of CFRPEs.The main research contents are as follows:(1)Use DMMP,HPCTP,FR-7016,GO flame retardant to modify epoxy resin.The results showed that the vertical combustion of the flame-retardant modified resin system has been upgraded from NO Rating to UL-94V0 and UL-94V1 level.However,high-added HPTP flame retardant had poor compatibility with epoxy resin.The viscosity of the 15%GO resin system was measured as high as 2700 m Pa·s,which cannot be infusion at room temperature.The viscosity of other flame-retardant modified resin systems was below 800 m Pa·s,which conforms to the VARI process.(2)There were two curing stages for MDA-type benzoxazine modified epoxy resins under different proportions,so choose to cure in stages: 80℃*4H+190℃*1H.The flame retardant properties of modified BOZ-M-1,BOZ-M-2,BOZ-M-3,BOZ-M-4 can reach UL-94V0 level,the limiting oxygen index was greater than 30,and the viscosity was low.(3)80℃*2H+150℃*2H,80℃*2H+150℃*2H+190℃*1H,80℃*2H+150℃*2H+220℃*1H,80℃*2H+190℃*2H as four curing different temperatures to explored the thermomechanical properties and flame retardant properties of the cured product,and found that the Tg was only 66℃ under the first curing condition,and the curing was insufficient.In the third curing scheme,due to the high temperature,part of the DMMP is volatilized and the flame retardant performance is deteriorated.After comprehensive evaluation,it was found that the curing process at 80℃*4H+190℃*1H is the best.(4)Using neopentyl glycol glycidyl ether to adjust the viscosity of the system,the viscosity adjustment effect was good,but it was the result of the deterioration of the flame retardant performance and the decrease of Tg.(5)Through different kinds of benzoxazine modified epoxy resins,the carbon residue rate tested by TGA increased by 113.6%,the thickness of the carbon layer increased from 10 mm to 60-70 mm,the total heat release tested by the cone calorimeter was reduced by 107%,and the heat release rate was also reduced by 180% on average.And vertical combustion can pass UL-94V0 level.Therefore,all epoxy resins modified by benzoxazine have excellent flame retardant properties.The DHR tested its operating period at 40℃,and it has a good operable period.(6)F-BLANK,F-DHU3,F-DHU4 manufactured by the VARI process,among which the heat release rate of the unmodified epoxy resin composite board was as high as 406KW/J,while the heat release rate of F-DHU3 was reduced by 147% to only 167KW/J,and the heat release rate of F-DHU4 was only 247KW/J,and the total heat release of the unmodified epoxy resin composite board was as high as 49KW/J.The total heat release of the flame-retardant modified F-DHU3 and F-DHU4 was only 31KW/J and 32KW/J.