Design Of DOPO-based Flame Retardant Containing P/N Elements And The Properties Of Flame Retardant Modified Epoxy Resin

Epoxy resin is widely used in daily life and engineering as a high-performance material with excellent performance.However,with the improvement of people’s safety awareness,the shortcomings of flammability have been paid more and more attention,which limits its application range.In this paper,the purpose is flame retardant modification of epoxy resin to overcome the flammability of epoxy resin and shortcomings of existing in the flame retardant modification such as damage to the mechanical and thermal properties of epoxy resins.Two kinds of P/N-containing elements reactive DOPO-based flame retardant are synthesized for flame retardant modified epoxy resins.The primary research details include:1、Based on the Atherton-Todd reaction mechanism,a DOPO-based flame retardant（AEPO）with piperazine structure was synthesized by 9,10-dihydro-9-oxa-10-Phospha-Phenanthrene-10-oxide（DOPO）and N-（2-Aminoethyl）piperazine and characterized the structure of AEPO.Then,a flame retardant epoxy resin was prepared by using AEPO as a flame retardant,4,4-diaminodiphenylmethane（DDM）as a curing agent and E44 epoxy resin as a matrix.The results show that the LOI value of flame retardant epoxy resin with10wt%AEPO can reach 35.5%and pass the UL-94 test V-0 rating.At the same time,its flexural strength,impact strength and tensile strength increased by 29.45%,73.64%and67.85%,respectively,compared to pure epoxy resin,and also showed good transparency.However,the AEPO flame-retardant modified epoxy resin will be pyrolyzed early.2、A multi-element synergistic flame retardant（PPVSZ）containing P/N/Si was successfully synthesized through the reaction between P-H of DOPO and-CH=CH₂ of polysilazane（PVSZ）.And,a flame retardant epoxy resin with excellent comprehensive performance is prepared with PPVSZ as flame retardant.It was found that PPVSZ simultaneously improved the thermal,flame retardant and mechanical properties of the epoxy resin.Among them,the flame retardant epoxy resin only with 2.5 wt%PPVSZ,its residual carbon at 700℃and T_g were increased by 5.61%and 9℃.At the same time,its LOI value reached 30%and passed the V-0 rating of the UL-94 test.In addition,the cone calorimetry test showed that the total heat release and total smoke were reduced by36.90%and 43.70%,respectively,indicating that the PPVSZ has obvious flame retardant and smoke suppression effects.3、A flame retardant epoxy resin composite material was prepared with PPVSZ as flame retardant,epoxy resin as matrix and glass fiber as reinforcement,and using hand lay-up process combined with hot press forming technology.The results show that the composite material has excellent flame retardant and mechanical properties.the limiting oxygen index of the composite with 5 wt%PPVSZ reached 43.2%and passes the V-0rating of UL-94 test.In addition,compared with EP/GF,the flexural strength,impact strength and tensile strength increased by 9.77%,59.85%and 24.13%,respectively,thanks to PPVSZ improving the infiltration and encapsulation ability of epoxy resin to glass fiber woven fabric.