| Epoxy resin is a versatile material with excellent comprehensive performance,whose flame retardant performance determines the field of engineering application.In this paper,for the purpose of flame retardant epoxy,a type of halogen-free,phosphorus and nitrogen synergetic flame retardant SD-DOPO was synthesized by the principle of molecular design,which was introduced into epoxy resin as a curing agent to prepare the flame retardant epoxy resin containing P-N.The micro structure and properties of the flame retardant and flame retardant/epoxy resin composites were characterized by FT-IR,~1H NMR,SEM,TGA,LOI test,DSC and so on.The flame retardant SD-DOPO was synthesized by covalently bonding DOPO and imine SD obtained from the condensation of diaminodiphenyl methane and salicylaldehyde.The molecular structure of SD and SD-DOPO was characterized by FT-IR and ~1H NMR.The content of elements contained in the molecule was tested by elemental analysis,the results show that the ratio of hydrocarbon to carbon and nitrogen content is close to the theoretical value.XRD test and DSC test showed that the two substances were all crystallized structure,the imine SD crystallized completely,the flame retardant SD-DOPO was not completely crystallized,which exist the amorphous region,the melting point of the two substances is about 200?,the flame retardants began to melt at 181?,indicating that the flame retardant has good heat resistance.The thermal analysis test showed that the residual carbon rate of SD-DOPO was higher than SD,22.85%at 700?,indicating that the flame retardants could better participate in the pyrolysis of the flame retardant,thus making the flame retardants better dehydrating the charcoal ability.Adding different content of flame retardant to epoxy resin,the thermal analysis test showed excellent thermal stability and with the increase of the addition,the decomposition rate decreases.The initial thermal decomposition temperature of the series epoxy resin was higher than 310?.The LOI test and conical calorimetry test showed that when adding 10%,the LOI value was 32%,reached UL94 V-0 grade,indicating that the flame retardancy was excellent.Tensile tests showed that epoxy cured at room temperature exhibited brittle fracture without yield deformation.Through the analysis of the structure and morphology of the carbon layer after combustion,the flame retardant mechanism of the epoxy resin was obtained.After the sample was heated,the phosphorus and nitrogen elements in the structure were split into phosphorus compounds,nitrogen compounds and phospho nitrogen compounds respectively.Phosphorus compounds can form molten glass on the surface of the polymer and play a role in mass transfer,heat transfer barrier,and a kind of carbon-forming promoter,and some phosphorus nitrogen compounds are better phosphorylation agents than phosphides.And Nitrogen compounds can delay the volatilization of phosphides,enhance phosphorus oxidation and release inert gases including ammonia,dilute the concentration of combustible particles and inhibit combustion,and the two can play a good role in synergistic flame retardancy. |
PDF Full Text Request