Preparation Of Aluminum-based Curing Agent And Intrinsic Flame Retardant Epoxy Resin

Epoxy resin（EP）,as a traditional thermosetting resin,has excellent mechanical properties,adhesive properties,solvent resistance,and thermal insulation properties,and is widely used in adhesives,coatings,electronic products,aerospace components,marine systems,and other fields.However,the flammability of epoxy resin cured products greatly limits their application potential.Nano alumina is inexpensive,environmentally friendly,and has various excellent properties,which can serve as a flame retardant for epoxy resin.However,the poor dispersibility after a large amount of addition can deteriorate the mechanical properties of epoxy resin,making it difficult to meet practical needs.This paper aims to enhance the flame retardancy of epoxy resin and improve the mechanical degradation caused by alumina filled epoxy resin.The main research work is as follows:1.Aluminum-based curing agent（CEPPA-AO）was prepared by the reaction ofγ-alumina with 2-carboxyethyl phenyl hypophosphoric acid.CEPPA-AO was introduced into the epoxy resin prepolymer to prepare epoxy resin with the intrinsic flame retardant properties.In the cone calorimetry test,EP-4 decreased by 25.4%,30.8%,14.3%,42.9%,39.1%and 35.5%respectively compared with p SPR,TSP,p COP,p CO₂P,p HRR and THR of EP.The results showed that the flame retardant properties of the epoxy resin were improved.And CEPPA-AO played a synergistic phosphorus-aluminum flame retardant effect on the epoxy resin.The flexural strength and flexural modulus of EP-3 were improved by 186.0%and 131.0%,respectively,compared with pure EP.The alumina was connected to the organic material through chemical bonding,which abated the agglomeration and interfacial interaction and eliminated the influence of the flexural properties of the material caused by the addition of large amount of inorganic material.2.Aluminum based curing agent（BPA-AO）was prepared by the reaction ofγ-alumina with phenylphosphoric acid,and the test results of X-ray powder diffraction test,Fourier transform infrared spectroscopy,and scanning electron microscopy all proved that BPA-AO had been successfully synthesized.The thermogravimetric test showed that the residual carbon of EP-6 at 800°C was greatly enhanced compared with the pure sample.In addition,the flame retardancy of intrinsic flame retardant epoxy resin was investigated.The EP-6 has the best overall flame retardant performance when compared with methods of limiting oxygen index test,horizontal vertical combustion test,and cone calorimetry test.PBA-AO and APP mainly exert flame retardant effects in the gas and condensed phases,playing a phosphorus-nitrogen-aluminum synergistic flame retardant effect.In the meantime,the flexural properties of the samples were tested by electronic universal testing machine,and the flexural strength and flexural modulus of EP-6 intrinsic epoxy resin were improved by 183.0%and 213.2%,respectively,compared with pure EP.The flexural properties were greatly improved by the synergistic use of PBA-AO and APP.3.Three different structures of phosphorus-nitrogen substances were used to react withγ-alumina to obtain three new nitrogen-phosphorus-alumina curing agents.The curing agents and APP were introduced into the epoxy resin prepolymer to prepare the intrinsic flame retardant epoxy resin material.And EP-6 has the best comprehensive performance.In the cone calorimetry test,the p HRR,THR,SPR,TSP,p COP,and p CO₂P of EP-6 decreased by 75.9%,25.1%,55.0%,19.8%,70.2%,and 76.8%.The ultimate oxygen index of EP-6 reached 25.8%,and EP-6 passed the V-0 grade of UL-94 in the horizontal vertical combustion test.The mass of the disability of EP-2,EP-4 and EP-6 at 800℃was 19.2%,16.9%,and 19.1%,while EP was 10.1%.The curing agent and APP played the flame retardant role together in the gas phase and condensed phase,and played a phosphorus-nitrogen-aluminum synergistic flame retardant role.the flexural performance of EP-6 was tested,and the flexural strength,and flexural modulus were improved by 168.6%and 214.6%,respectively,compared with pure EP.The flexural performance was greatly improved by the synergistic use of C-AO and APP,and the application range of epoxy resin was broadened.