含亚胺结构新型磷-氮协效阻燃化合物的合成及对环氧树脂的阻燃作用

采用醛胺缩合反应,以4-(5,5-二甲基-1,3-二氧杂环己内磷酰基)苯甲醛(PCHO)分别与对苯二胺、乙二胺反应合成两种磷酸酯-亚胺双官能化合物阻燃剂(FR:N¹,N⁴-二4-(5,5-二甲基-1,3-二氧杂环己内磷酰氧基)苯基亚甲基]-1,4-苯二胺(PNB)和N¹,N²-二4-(5,5-二甲基-1,3-二氧杂环己内磷酰氧基)苯基亚甲基]-1,2-乙二胺(PNE)),研究了FR对4,4'-二氨基二苯砜(DDS)固化双酚A二缩水甘油醚型环氧树脂(DGEBA)体系的阻燃作用及阻燃机理。 研究发现FR的引入显著提高了DGEBA/DDS在700 ℃时的残炭率(R_c),同时提升了材料的阻燃性能,其中以乙二胺合成的PNE阻燃性能显著优于以苯二胺合成的PNB。 当磷添加质量分数为1.5%时,PNE-1.5/DGEBA/DDS在N₂气下的R_c为35.1%,在空气下的R_c为14.4%,极限氧指数(LOI)为33.2%,并可达阻燃等级UL-94最高阻燃级别V-0级。 同时,PNE-1.5/DGEBA/DDS相较于DGEBA/DDS保持了弯曲强度和76%以上的冲击强度,机械性能显著优于PNB-1.5/DGEBA/DDS。 通过阻燃机理分析FR在DGEBA/DDS体系中具有凝聚相、气相及磷-氮协效共同作用的阻燃特点。 磷酸酯-亚胺双官能团化合物FR对环氧树脂体系具有良好的阻燃作用,其中PNE阻燃效率高、机械性能负面影响小,具有潜在应用价值。

Synthesis of Phosphorus-Nitrogen Synergistic Flame-Retardant Compounds with Imide Structure and Their Flame Retardant Effect on Epoxy Resin

Two novel phosphate-imine bifunctional flame-retardant compounds(FR:N 1,N 4-bis{4-(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphinan-2-yl)oxy]benzylidene}benzene-1,4-diamine(PNB);N 1,N 2-bis{4-(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphinan-2-yl)oxy]benzylidene}ethane-1,2-diamine(PNE))were synthesized via aldehyde amine condensation reaction using 4-(5,5-dimethyl-1,3-dioxygen heterocyclic phosphoryl)benzaldehyde(PCHO),p-phenylene diamine and ethylenediamine as raw materials,respectively.FRs were applied on a bisphenol-A diglycidyl ether type epoxy resin(DGEBA)cured by 4,4′-diaminodiphenylsulfone(DDS)and the flame retarded mechanism was studied.The results showed that the introduction of FR greatly improved the char residues(R c)of DGEBA/DDS at 700℃ and enhanced the flame retardant properties of epoxy resin systems.PNE with ethylene diamine unit presented a better flame retardant performance than PNB with p-phenylene diamine unit.With 1.5% phosphorus content,PNE-1.5/DGEBA/DDS could obtain R c of 35.1% in nitrogen atmosphere and 14.4% in air,respectively,and a limiting oxygen index(LOI)value of 33.2%,reaching UL-94 V-0 grade.At the same time,PNE-1.5/DGEBA/DDS maintained the bending strength and more than 76% of the impact strength compared to DGEBA/DDS,which is significantly superior to PNB-1.5/DGEBA/DDS.Analysis of flame retardant results showed that FR presented a comprehensive mechanism of condensed phase,gas phase and phosphorus-nitrogen synergistic effect in DGEBA/DDS system.In conclusion,phosphate-imine bifunctional compounds FR have excellent flame retardancy for epoxy resin systems and have potential applications.