Effect of Salicylaldehyde Schiff base flame retardant on thermal performance and flame retardant performance of EP
In order to explore the effect of different P/N contents on the flame retardant properties of EP composites and the effect of different Schiff Bases functional groups on the thermal proper-ties of EP composites,three new phosphorus-containing Schiff Bases flame retardants of SAPO,SPPO and SMPO were pre-pared using salicylaldehyde(SAL),3-amino-1,2,4-triazole(ATZ),p-phenylenediamine(PPD),melamine(MEL)and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)as raw materials,SAPO is triazole-Schiff Base flame retardant,SPPO is benzene ring-Schiff Base flame retardant,SMPO is triazine-Schiff Base flame retardant.1H-NMR and FT-IR were used to characterize the structures of the three flame retardants,and the successful synthesis of the three flame retardants was dem-onstrated.The three flame retardants are not only different in structural composition,but also in the number of Schiff base func-tional groups:1 mol SAPO,SPPO,SMPO contain 1 mol,2 mol,3 mol Schiff base functional groups,respectively.Vertical combustion testing,limiting oxygen index testing,thermo-gravimetric analysis and Cone calorimetry testing were used to ex-plore the thermal properties and flame retardant properties of EP composites.The results showed that the vertical combustion test-ing of EP/6% SAPO,EP/6% SPPO and EP/6% SMPO all reached V0 level,the LOI values reached 32.9%,32.3%,33.5%,respectively,the carbon residue increased to 23.6%,24.7%,25.1%,respectively,the PHRR values decreased by 20.2%,25.8%,27.9%,respectively,the THR values de-creased by 15.2%,17.8%,20.3%,respectively.The flame re-tardant properties of EP composites increased with the increase of P/N content.The thermal properties are enhanced with the in-crease in the number of Schiff Bases functional groups.The flame retardant mechanism is mainly attributed to the capture of free radicals by P element in the gas phase,the chain reaction of cut-ting off the chain,and the promotion of carbonization and dehydra-tion in the condensed phase to form a carbon layer,which isolates gas exchange and heat conduction.N element releases non-combustible gas when burned,reducing the concentration of com-bustible gas and taking away heat.
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