Preparation And Properties Study On Flame Retardant And Conductive Epoxy Resin Composites

Epoxy(EP)is a thermoset polymer with a variety of excellent properties,high tensile strength and young’s modulus,excellent size,good thermal stability,good solvent resistance,low cost,easy to processing.And has been widely used as coating matrix,adhesives and composites.However,the low electrical conductivity and poor flame retardancy of epoxy resin limit its widely application in key areas.Pure EP is an insulating and flammable material,limiting oxygen index(LOI)only about 25%.Therefore,its flame retardant and conductive modification to increase its application in the market is critical.At present,the choice of flame retardant is being developed towards environmental protection,sustainability,low toxicity and high efficiency.In order to minimize the impact of the filler on the mechanical properties,conductive filler also tend to choose carbon nano-materials.In this subject,pretreatment of flame retardant and conductive filler in the first.Then,using additive processing methods for the preparation of composites materials,and studied the flame retardant properties,electrical conductivity,mechanical properties.The main research work is as follows:1.Ammonium polyphosphate(APP)as a flame retardant additive and its microcapsule coating modified with 4,4-diaminodiphenylmethane as a curing agent,the use of thermosetting method to prepare a different content of the flame retardant EP composites.After adding EAPP,it was found that the dispersion in the matrix was better than that of pure APP.With the increase content of EAPP,the combustion performance of EP/EAPP composites improved,the LOI increased from 25.1%to 43.3%,and the UL-94 reached the V-0 level.2.EP/EAPP/CNTs/GS flame retardant conductive composites were prepared by melting and blending EAPP,carbon nanotubes and graphite sheets in different proportions.The results show that adding 3 phr of carbon nanotubes and graphite sheet can improve the electrical conductivity of epoxy resin,and when the ratio of the two is 8:2,the electrical conductivity is the best,and the electrical conductivity is 6.61 × 10-3 S/cm;however,the maximum oxygen index of the material can only be increased to 28.6%at this time,mainly because the thermal conductivity of the system is better,resulting in faster thermal diffusion of the material and indirectly promoting combustion.Therefore,the UL-94 can only achieve V-2 level.3.Multi-walled carbon nanotubes(CNTs)were treated with a silane coupling agent(KH-560).Then,EP/CNTs/GS hybrid nanocomposites were prepared by thermoset polymerization.Conclusions as below:the flame retardancy,electrical conductivities,mechanical properties and thermal stabilities of the CNTs/EP nanocomposites were all improved with the increasing addition of two-dimension graphite sheet(GS)fillers.While the two reach a certain percentage of time,characterizations will achieve the best results.The electrical conductivity was increased to 8.86×10-3 S/cm(the ratio of GPTs-CNTs/GS is 8:2),far better than that of pure EP matrix composites(1.0×10-12 S/cm).And cone calorimeter results revealed that the total heat release(THR)and heat release rate(HRR)was decreased 36.0%and 27.1%respectively while 15wt%GPTs-CNTs/GS fillers was added.Conversely,the peak of heat release rate of the GPTs-CNTs/EP nanocomposite became worse due to its high thermal conductivity.