Preparation Of Cyclophosphazene-based Epoxy Resins And Study Of Its Performance

Cyclophosphazene is a kind of compound with a six-membered ring formed by alternately connecting single and double bonds of phosphorus and nitrogen atoms.Nucleophiles attack and substitute to prepare cyclophosphazene compounds of various structures.In addition to the inherent flame retardant properties of cyclophosphazene compounds,their high degree of functionalization is also used to prepare functional resin material intermediates for modifying the fire safety of traditional materials.Based on these research backgrounds,in this paper,two new types of cyclophosphazene-based epoxy resins and reactive flame retardants were prepared by structural design and organic and polymerization chemical reactions using phenol,methanol,4-allyl-2-methoxyphenol,hexachlorocyclotriphosphazene and other raw materials.The paper mainly includes the following aspects:（1）Through structural design,two intermediates containing double bonds,tris（phenoxy/4-allyl-2-methoxyphenoxy）cyclophosphazene（CP-3D）and tris（phenoxy methoxy/4-allyl-2-methoxyphenoxy）cyclophosphazene（CP-3MD）were first prepared.And the structure of the obtained products were characterized by nuclear magnetic resonance（NMR）and mass spectrometry,confirming the success of the two intermediate products preparation.Furthermore,cyclophosphazene epoxy monomers were efficiently prepared by double bond epoxidation.Fourier transform infrared spectrometer and NMR characterizations verified that the structure of aryloxycyclophosphazene epoxy monomers（CP-EP-M）and methoxy/aryloxycyclophosphazene epoxy monomer（CP-MEP-M）.The thermal stability of two epoxy monomers were characterized using thermogravimetric analyzer（TGA）.Compared with CP-MEP-M,CP-EP-M has higher initial decomposition temperature(T_onset)and maximum decomposition rate corresponding temperature(T_max),and has better thermal stability.（2）The curing reaction kinetics of CP-EP-M cured with succinic anhydride（SA）,methylhexahydrophthalic anhydride（Me HHPA）and diaminodiphenylmethane-diethyltoluenediamine（DDM+DETDA）were investigated.The glass transition temperature（T_g）the cured aryloxycyclophosphazene epoxy thermosets（CP-EP）are higher than those of E44,and all reach V-0 level in the UL-94 test.The peak heat release rate（PHRR）,total heat release（THR）and total smoke production（TSP）of CP-EP cured with DDM+DETDA decreased by 34%,50%and 56%,respectively,compared to the control E44 sample,the char yield increased by 400%.At the same time,the tensile strength and flexural strength of CP-EP are improved by about 10%and 20%respectively compared with the E44 control sample.（3）The modified epoxy resins（CP-MEP-5,10,15 and 20）were obtained by adding CP-MEP-M as a monomer to the E44/DDM system for curing.The kinetics of the curing reaction under different addition amounts were investigated experimentally,and it was found that the limiting oxygen index（LOI）value of the CP-MEP-20 system with a phosphorus content of 2.0 wt.%was as high as 31.0%.The introduction of CP-MEP-M can increase the g T_g and700°C char yield of the epoxy system.Compared with pure E44,CP-MEP-20’T_g and 700°C char yield increases by 13%and 88%,respectively.