Research On Flame Retardant And Smoke Suppression Properties And Mechanism Of Modified Ammonium Polyphosphate In Epoxy Resin

Epoxy resin（EP）,as a commonly used thermosetting engineering material,has important applications in the fields of national economy,national defense and military industry.However,pure EP is very easy to burn in the air.After being ignited,it burns violently with a lot of smoke and toxic gases,which seriously limits its application.In order to reduce the fire risk of EP and expand its application range,ammonium polyphosphate（APP）is taken in this work as the research object.Through the principle and technology of surface grafting modification and microcapsulation,three single-component intumescent flame retardants with excellent flame retardancy and smoke suppression performance are designed and prepared for the flame retardant modification of EP.The main work and achievements of this paper are as follows:（1）Diaminodiphenylmethane modified ammonium polyphosphate（DDP）was synthesized with APP and diaminodiphenylmethane（DDM）.Then DDP was characterized by Fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance(¹H-NMR,³¹P-NMR)and scanning electron microscopy（SEM）,and then was added to EP to prepare flame retardant EP.The effects of DDP on the flame retardant properties,char formation behavior,thermal stability and mechanical properties of EP were studied by LOI and UL94 tests,cone calorimeter（CCT）and thermal gravimetric analysis（TG）.It was found that when the DDP content was15 wt%,the LOI value of epoxy resin reached 37.1%and could pass UL94 V-0 test.The value of total heat release rate（THR）and peak heat release rate（PHRR）decreased by 32.3%and 40.8%compared with pure EP,respectively.In addition,DDP can effectively enhance the carbon formation ability of epoxy resin,and APP grafted with DDM can reduce the negative impact of APP on the mechanical properties of epoxy resin.（2）Reduced graphene oxide modified ammonium polyphosphate（RGO-APP）was prepared from graphite oxide,APP and ascorbic acid（LAA）.RGO-APP was characterized by FTIR and SEM.The flame retardant EP was prepared by blending RGO-APP with EP.The effects of RGO-APP content on the flame retardancy,charring behavior,thermal stability and mechanical properties of flame retardant EP were studied.The results showed that RGO-APP showed higher flame retardant efficiency in epoxy resin compared with the simple blending of APP and RGO.In addition,RGO-APP showed better surface adhesion and compatibility with EP matrix,and promoted the formation of more phosphorus compounds in the combustion process to effectively enhance the mechanical properties and flame retardant and smoke suppression properties of epoxy resin.When the addition amount was 15 wt%,the LOI value of the flame retardant epoxy resin reached 35.8%,and it could pass UL94 V-0 test.Compared with pure EP,the value of THR,PHRR,TSR and PSPR of the flame retardant epoxy resin decreased by 62.6%,83.5%,28.7%and 74.3%,respectively.（3）Microencapsulated single-component intumescent flame retardant（PPy-MAPP）was synthesized by using APP,melamine（MEL）and pyrrole（Py）as main raw materials,and its structure was characterized by FTIR and SEM.Flame retardant EP was prepared by blending PPy-MAPP with EP.The effects of PPy-MAPP content on the flame retardancy,charring behavior,thermal stability and mechanical properties of flame retardant EP were studied.The results showed that coating with PPy could further improve the flame retardant and smoke suppression efficiency of melamine modified ammonium polyphosphate（MAPP）.When adding 15wt%PPy-MAPP,the LOI value of flame retardant EP can reach 42.4%,and can pass UL94 V-0 test,while the value of TSR and TSP decreased by 58.0%and 62.2%respectively compared with pure EP.The addition of PPy-MAPP improved the phosphorus content and integrity of the carbon layer.DSC and mechanical properties test showed that PPy-MAPP had satisfactory compatibility with EP and had little negative effect on mechanical properties of materials.There are 46 figures,15 tables and 99 references.