Synthesis Of Four Phosphorus-nitrogen Containing Flame Retardants And Their Application In Epoxy Resins

Halogen free flame retardant has become a key issue of epoxy resin of highperformance. Flame retadardant epoxy resin containing phosphorus or nitrogen hasaroused extensive attention, because of its low toxicity, no halogen, high flameretardant efficiency and others performance. In the thesis, the synthesis of fourphosphorus-nitrogen containing flame retarandts and their application in epoxy resinswere described and discussed.Three imine intermediates were synthesized by the condensation ofp-phenylenediamine with benzaldehyde,4-hydroxybenzaldehyde and2-hydroxybenzaldehyde respectively, followed by the addition of9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the imine linkage, threekinds phosphorus-nitrogen compounds （BBP-DOPO, BHP-DOPO, BSP-DOPO）containing active hydrogen were synthesized. The structures of the three compoundswere characterized by FTIR, NMR and MS.The three phosphorus-nitrogen compounds served as co-curing agents ofdiaminodiphnylmethane for epoxy resins, three epoxy curing system were obtained.The glass transition temperature （T_g） of epoxy thermosets were measured bydifferential scanning calorimeter （DSC）. As a result, with the addition amount of flameretardant increasing, T_gvalues of epoxy thermosets decreased. In the same condition ofphosphorus content, T_gvalues were in an order: BHP-DOPO epoxythermosets>BBP-DOPO epoxy thermosets>BSP-DOPO epoxy thermosets, and T_gvalues of three epoxy thermosets were more than130℃.Thermal stability of epoxy thermosets was researched through thermogravimetricanalysis （TGA）. The results show as follows: with the increase amount of flameretardant, initial decomposition temperature (T_d,5wt.%) of epoxy thermosets graduallydecreased, but the char yields gradually increased. In the same condition of phosphoruscontent, T_d,5wt.%and char yields values were in an order: BHP-DOPO epoxythermosets> BSP-DOPO epoxy thermosets> BBP-DOPO epoxy thermosets, andT_d,5wt.%of three epoxy thermosets were more than320℃.UL94vertical burning test and limited oxygen index （LOI） method were used to investigate flame-retardant properties of epoxy thermosets. The results show as follows:with the increase amount of flame retardant, LOI values of epoxy thermosets graduallyincreased, and all the epoxy thermosets exhibit excellent flame retardancy. When thephosphorus content is1.0wt.%, UL94V-0grade of thermosets can be achieved, andLOI values reached more than35. In the same condition of phosphorus content, LOIvalues were in an order: BSP-DOPO epoxy thermosets> BHP-DOPO epoxythermosets> BBP-DOPO epoxy thermosets.Based on the study of three phosphorus-nitrogen containing flame retardants,according to the copper clad laminate’s technology and processes, flame retardantTSFR-4was synthesized. Flame retardant TSFR-4was used in copper clad laminate（CCL）, and the CCL’s various properties were measured. The results show as follows:with the flame retardant TSFR-4gradually increased, CCL’s T_g, bending strength, peelstrength and thermal property gradually reduced, but flame-retardant propertygradually increased. When the phosphorus content is0.9wt.%and nitrogen content of4.7wt.%, UL94V-0grade of CCL can be achieved, and LOI values reached35.6. Thehalogen-free CCL possesses excellent comprehensive properties, and has a marketprospect.