Preparation Of DOPO Based Flame-retardant And Its Modification Of Epoxy Resin

Epoxy resin(EP)has excellent formability,corrosion resistance,and electrical insulation properties,and is a thermosetting resin with excellent comprehensive performance.It is widely used in aerospace,electronic circuits,national defense,military and other application fields.However,the rich carbon,hydrogen,and oxygen elements in epoxy resin determine its flammability,and when burned,it releases a large amount of toxic gases and smoke,posing a huge threat to people’s life and property safety.Therefore,flame retardant modification of epoxy resin is of great significance.Based on research concepts such as low smoke,low toxicity,green environmental protection,and high flame-retardant efficiency,this paper designed the structure of flame retardants and prepared three types of 9,10-dihydro-9-oxa-10-phosphophenyl-10-oxide(DOPO)derived synergistic flame retardants.Through testing and application in epoxy resin,it was proven that they have high flame retardancy.The main research content was as follows:1.A phosphorus/nitrogen containing silane compound(D)was synthesized using polyformaldehyde,KH-550,and DOPO as raw materials through the Kabechnik-Fields reaction,and D was grafted onto the surface of graphene after hydrothermal treatment to obtain a nano hybrid flame retardant D-GR.The vertical combustion test(UL-94)showed that 1% D-GR/EP passed the V-1 level of the UL-94 test.The cone calorimetry(CC)test showed that the peak heat release rate(PHRR)and total smoke release(TSP)of 1% D-GR/EP decreased by 44.3% and 28.6%,respectively,compared to the pure sample.The mechanical properties showed that the mechanical properties of the modified epoxy resin can be well maintained at low flame-retardant content.Comprehensive analyses such as Raman,pyrolysis gas chromatography/mass spectrometry(Py-GC/MS),and scanning electron microscope(SEM)have shown that D-GR/EP residual carbon has good compactness,high degree of graphitization,and the flame-retardant mechanism was mainly manifested as condensed phase flame retardant.2.In order to further improve the flame retardancy of EP composite materials and maintain their good thermal properties,a new high-efficiency organic flame retardant APH was synthesized using KH-550,p-benzaldehyde,1,5-diaminonaphthalene,and DOPO as raw materials through the Kabechnik-Fields reaction.Through mechanical performance testing,it was found that the impact performance of 1% APH/EP increased by 15.0% compared to EP.Thermal performance tests showed that the residual carbon content and glass transition temperature(Tg)of APH/EP were improved.The CC test results showed that the PHRR and TSP of 4% APH/EP decreased by 34.1% and 38.4%,respectively.Thermogravimetric infrared spectroscopy(TG-FTIR)and Raman testing indicated that the APH/EP composite material exhibits high residual carbon regularity and reduced volatile gas release,mainly exhibiting a condensed phase flame retardant mechanism.3.In order to further improve the flame-retardant efficiency,the synthesized APH was combined with ZIF-8 to synthesize the organic metal flame retardant APHZ.The effect of APHZ on the flame retardancy,thermal properties,and mechanical properties of flame-retardant epoxy resin was systematically studied.At a dosage of 3 wt%,the composite material passed the V-0 level tested by UL-94,and the limit oxygen index(LOI)value increased to 30.7%.The CC test results showed that the addition of APHZ exhibits good smoke suppression effect.Through tests such as Raman,X-ray diffraction spectroscopy(XPS),and TG-FTIR,it has been proven that the residual carbon of APHZ/EP has a high degree of graphitization,exerted the flame retardant effect of the condensed phase,and improved the flame retardant efficiency.