Study On Short-cut Carbon Fiber Reinforced Flame Retardancy Of Phenolic Epoxy Resin

Phenolic resin is widely used in friction materials,aerospace and other fields because of its good heat resistance,flame-retardancy and electrical insulation.However,its application in some fields is limited because of its poor toughness and brittleness.Therefore,how to improve its mechanical properties without reducing its flame-retardancy has become a technical problem in this field.Epoxy resin is widely used in fuselage wainscotting because of its excellent mechanical properties and good cohesiveness.Carbon fiber has the advantages of high strength,good heat resistance and less density,which is often used as the reinforcement of high-performance composite materials.In this paper,epoxy resin and short-cut carbon fiber were used as reinforcements to modify the flame-retardancy and toughening of phenolic resin.Phenolic epoxy resins with different proportions were prepared by physical blending method,and then carbon fibers were introduced into the resin matrix by in-situ polymerization.The flame-retardancy and thermal stabilization of each sample were analyzed by oxygen index meter,cone calorimeter and thermogravimetric analyzer(TGA).The tensile properties of each sample were tested by mechanical tensile test,and the microstructure of each sample was observed by scanning electron microscope(SEM),so that the mechanism of carbon fiber modification was explored.The results showed,when the proportion of epoxy resin was 5%,the flame-retardancy of phenolic epoxy resin decreased slightly,the oxygen index decreased 6.3%,the ignition time advanced 66 s,and the peak heat release rate(HRR)increased 8.9%.The time of 20%-mass loss of thermogravimetric experiment was advanced by 39 s,and the temperature decreased by 6.1?.In addition,the mechanical properties of the material were improved significantly,and the tensile properties and elastic modulus were increased by 46% and 26.1% respectively.When the proportion of short-cut carbon fiber was 0.5%,the best flame-retardancy and mechanical properties of phenolic epoxy resin were obtained.The oxygen index was increased by 4.6%,the ignition time was delayed by 35 s,and the peak heat release rate was decreased by 18.9%.At 800 ?,the char yield was increased by 60.4%,the apparent activation energy was increased by 11.3%,the tensile properties and elastic modulus was increased by 90.4% and 87.9%,respectively.The microstructure observation showed that the addition of carbon fiber promoted the carbonization of the material so as to make its structure more stable and firm.