Study On Properties Of Flame Retardant Galss Fiber Reinforced Epoxy Composites Modified By Ammonium Polyphosphate

Glass fiber reinforced plastics（GFRP）is widely used in aerospace,ship,rail transit and many other fields due to its high strength,excellent corrosion resistance,wave permeability and flexible processability.Among various thermoset polymers,epoxy resin is one of the most widely used polymer matrix for GFRP.Although epoxy resin has good cohesiveness,mechanical properties and low curing shrinkage,the flammable nature of unmodified epoxy resins greatly limites the application GFRP.In this dissertation,inrumescent flame retardant systems were used to modify epoxy resin.The effects of ammonium polyphosphate（APP）and associative systems which consist of APP,melamine（MA）and triazine-type char-forming agent（CFA）on the flame retardantcy and other physical properties of epoxy resin were systematically investigated.Finally,the properties（especially the flame retardant properties）of GFRP using flame retardant modified epoxy as matix was studied.The main research contents and results of this dissertation are shown as follows:Firstly,the effects of different contents of APP on the rheological property,curing behavior,mechanical property,thermo-mechanical peoperty,wet heat aging and flame retardancy of the epoxy resin were investigated.The results show that the viscosity of epoxy resin increased with the increase of APP content.When the APP content was 40wt%,the viscosity of the resin reached721mPa.s,and the pot life was 80 min.Different contents of APP had no significant effect on the curing behaviors of epoxy resin,and the curing conditions were determined to be80℃×4h+140℃×2h.With the increase of APP content,the glass transition temperature（T_g）of the cured epoxy resin showed an increasing trend,and the tensile modulus of elasticity increased obviously,but the tensile strength decreased.The tensile strength of the cured epoxy resin was49.5 MPa when the loading of APP was 40wt%.The addition of APP significantly enhanced the flame retardant properties of epoxy resin.When filler loading of APP was more than 20wt%,all the cured epoxy samples could reached UL-94 V0 vertical combustion level.It is noteworthy that the cured epoxy resin with 40wt%APP showed very high limit oxygen index（LOI）of 47.3%.Secondly,the total amount of flame retardant was fixed to 40wt%,and the effects of APP/MA,APP/CFA,and APP/MA/CFA associative flame retardants on epoxy resin performance were studied.The epoxy samples with associative flame retardants showed similar curing behaviors,thermo-mechanical and mechanical properties compared with those with only 40wt%APP.When the weight ratio of APP:MA and APP:CFA was 3:1,the flame retardant performance of epoxy samples were slightly better than those only with APP.When the weight ratio of APP:MA:CFA was 6:1:1,the epoxy sample showed the best flame retardantancy.Compared with unmodified epoxy resin,the LOI increased from 18.0%to 50.2%,the peak heat release rate（PHRR）decreased from 1056kW.m^-22 to 200kW.m^-2,the total heat release（THR）decreased from110 MJ.m^-22 to 24 MJ.m^-2,and the thickness of the expanded carbon layer during burning could reach the maximum 113 mm.Finally,APP（40wt%）and APP（30wt%）/MA（5wt%）/CFA（5wt%）modified epoxy resins were used as the matrices to fabricate GFRP by hand lay-up process.The influences of epoxy modification on the thermal-mechanical properties,mechanical properties and flame retardancy of GFRP were investigated.The results showed that the mechanical properties of both modified GFRP degraded,but the retention of flexural strength and flexural modulus is still above 80%.Both the modified GFRP showed slightly improved heat resistance,and their T_g increased by 5oC.Compared with the unmodified GFRP,the GFRP modified by APP/MA/CFA showed much better flame retardancy.After modification by APP/MA/CFA,the LOI increased from 22.8%to 66.0%,the PHRR decreased by 74%,the THR decreased by 53%,and peak smoke produce rate（SPR）decreased by 36.5%,respectively.