The Flame Retardant Properties And Mechanism Of The Compounds Based On Phosphaphenanthrene And Triazine Groups In Epoxy Resin

To satisfied the demand of electrical and electronic fields for the high-efficiency and environmentally friendly flame retardant epoxy resin, the tri-(phosphaphenanthrene-(hydroxyl-methylene)-phenoxyl)-1,3,5-triazine(Trif-DOPO),tri-(3-phosphaphenanthrene-2-hydroxy-propyl)-1,3,5-triazine-2,4,6-trione(TGIC-DOPO)and TGIC-ODOPB-DOPO(TOD) three compounds based on phosphaphenanthrene and triazine groups were prepared in this topic. Meanwhile, the flame-retardant behaviors and mechanism of aforementioned three compounds based on phosphaphenanthrene and triazine groups were studied in epoxy resin.1. Trif-DOPO was prepared through a two-step method utilising cyanuric chloride,p-hydroxy benzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) as basic reactants. The application results of Trif-DOPO in the bisphenol-A diglycidyl ether type epoxy resin(EP) cured by 4,4-diaminodiphenyl sulfone(DDS)indicated that Trif-DOPO/EP/DDS thermoset reached UL94 V-0 rating with a LOI value of 36.0% when the phosphorus content of thermoset achieved 1.2wt.%.Trif-DOPO showed a significantly higher flame-retardant efficiency than that of DOPO or triphenoxy-1,3,5-triazine in EP/DDS thermoset. The group synergistic effect between phosphaphenanthrene and triazine groups of Trif-DOPO was observed visibly in flame retarding epoxy resin thermoset.2. TGIC-DOPO was prepared through a one-step method from the addition reaction between 1,3,5-Triglycidyl isocyanurate(TGIC) and DOPO. The application results of TGIC-DOPO in the EP individually cured by 4,4’-methylenedianiline(DDM), DDS and m-phenylenediamine indicated that TGIC-DOPO exhibited the highest flame-retardant efficiency in EP/DDM thermoset. The EP/DDM thermoset containing4 wt.% TGIC-DOPO reached UL94 V-0 rating with a LOI value of 35.6%. Through inducing pyrolysis, promoting charring, free radical quenching and dilution effect of nonflammable gases, TGIC-DOPO endowed EP/DDM thermoset outstanding flame reatrdancy efficiently.3. The rich triazine group compounds melamine cyanurate(MCA) was adopted to co-work with TGIC-DOPO in flame retarding EP/DDM thermoset. Cooperating with extra3 wt.% MCA, the flame-ratardant rating of EP/DDM thermoset containing 1wt.%TGIC-DOPO was elevated from unrated level to UL94 V-1 rating. Compared withindividual TGIC-DOPO, The cooperation of MCA and TGIC-DOPO increased the ratio of triazine group, redistributed the distribution of flame-retardant effects between gas and condensed phases, improved the synergy of flame-retardant effects in two phases, and resulted in a higher flame-retardant efficiency.4. TOD oligomers in different degree of polymerization(DP) based on phosphaphenanthrene and triazine groups were prepared from TGIC,10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide(ODOPB) and DOPO. The flame-retardant efficiency of TOD oligomer decreased gradually with the increase of DP. When the DP of TOD oligomer was 1(TOD-1), the EP/DDM thermoset containing 4wt.% TOD-1 reached UL94 V-0 rating. With the increase of DP, the ratio of phosphaphenanthrene group in TOD oligomer reduced which wenkened the synergy of flame-retardant effect between gas and condensed phases and resulted in a lower flame-retardant efficiency.