Improving Flame Retardant Properties Of Epoxy Resin By Preparing Inorganic Nanoparticle Containing Phosphorus, Boron, Silicon, And Cobalt Elements

In this rapidly changing age of science and technology,our daily lives are almost filled with all kinds of polymer materials.As one of the most important auxiliaries for the application of polymer materials,flame retardants are always used to promote the thermal stability,to expand the application ranges as well as to prevent or delay the polymer materials from burning.In the flame retardant researches,to avoid the environment pollution in the traditional synthesis process and to abandon the halogen-based flame retardants that endanger the ecosystem are the main tasks of the current industry.Phosphorus,boron and nitrogen-containing flame retardants are the most widely used environmental flame retardants instead of the halogen-based ones.Nowadays,inorganic nanoparticles have received more and more attention in the field of flame retardant because of their prominent advantages.In addition,scientific researchers have also noticed that graphene and g-C₃N₄ can form strong and stable heat-insulating layer during their heat decomposition.However,some of their disadvantages including easy agglomeration,smoke producing,and polymer wear acceleration must be overcome when graphene and g-C₃N₄ are worked as flame retardant for polymer materials.At present,epoxy resin has occupied 80%of the domestic polymer material application market,but suffered from the disadvantages of brittleness and flammability.Hence,it is significant to synthesize flame retardant epoxy resin materials.Though inorganic flame retardants can enhance thermal stability of epoxy resin,they lead to the damage of mechanical properties of epoxy resin.Therefore,modifying the inorganic nanoparticles,regulating the microscopic morphology of the nanoparticles in order to improving the degree of crosslinking between the inorganic flame retardant and the epoxy resin,and avoiding damage to the polymer material is of very important.Based on this point,the main research of this paper are as follows:1.An effective ternary organic-inorganic hybrid flame retardant was developed by conducting oxidative polymerization of dopamine monomer within graphene oxide（GO）and then complexed with g-C₃N₄,ODOPB.The organic-inorganic hybrid flame retardant was then compounded with APP and reduced the flammability of EP.The structure and composition of the flame retardant were characterized by SEM,FTIR,XRD and ¹H-NMR.The flame retardancy and burning properties of composite were investigated by thermogravimetric analyzer（TGA）,limiting oxygen index（LOI）,vertical burning test（UL-94）and cone calorimeter test（CCT）.The microstructures of the residual char yield of EP composite were studied through SEM.It was found that the PHRR of the prepared composites（EP/GO-PDA@g-C₃N₄@ODOPB）reduced 35%when the ratio of GO-PDA,g-C₃N₄ and ODOPB was 1:1:3,compared to the pure EP.The obtained sample passed UL-94 V-0 rating with 20.0 wt%addition of GO-PDA@g-C₃N₄@ODOPB-APP.Furthermore,the composite gained the firm,continuous char yield,which increased from 45.57%to 90%,after combustion.2.Inorganic flame retardant nanoparticles MPB was prepared using phosphoric acid,boric acid and melamine as raw materials.GO was prepared according to the Hummers method,and then it was reduced by hydrazine hydrate and functionalized with P-N containing skeleton of HCCP,the RGO-HCCP nanosheets were successfully synthesized.RGO-HCCP@MPB flame retardant was obtained by simple co-precipitation method.RGO-HCCP@MPB-EP flame retardant composites were the prepared using diethylenetriamine as curing agent.It showed that RGO-HCCP@MPB enhanced the thermal stability of epoxy resin materials.It was considered that strong and stable thermal insulation layer was formed by graphene with the promotion of phosphorus-base flame retardants.On the other hand,the phosphorus-base flame retardants could release free radicals at high temperature,which inhibited the thermal cracking of matrix materials.The synergic flame retardant role was played both in gas and condensed phase.3.In order to investigate the effect of the microstructure of the flame retardant on the matrix,three kinds of Co（OH）₂ nanoparticles with different crystal morphologies were prepared and worked as flame retardants for improving heat resistance of epoxy resin.It turned out that the flower-like Co（OH）₂ prepared by solvothermal method showed the best performance.With the application of flower-like Co（OH）₂,the flame retardancy as well as the smoke suppression properties of epoxy resin have been significantly enhanced.