Synthesis of trifluoromethylbiphenyl epoxy resin and its high temperature resistance and flame retardant properties

A novel trifluoromethyl biphenyl epoxy resin monomer was synthesized through a diazo reaction and the etherification of hydroxyl groups with epichlorohydrin. Using 4,4 '-diamino-2,2 '-bis(trifluoromethyl)biphenyl as a self-curing agent, a new trifluoromethyl biphenyl epoxy resin (TFMB-EP/TFMB) was prepared. The structure was characterized by 1H NMR, 13C NMR, 19F NMR, and FTIR. The resin's thermal stability and flame retardancy were evaluated using TGA, DSC, DMA, limiting oxygen index, and cone calorimetry. Experimental results showed that this resin exhibited excellent heat resistance and flame retardancy, with a glass transition temperature (Tg) of 193 degrees C and a 5 % thermal decomposition temperature reaching 400 degrees C. The flame retardant performance, measured by LOI, was 31.5 %, achieving a UL-94 V0 flame retardant grade. Analysis of the resin before and after combustion using Py-GC/MS, XPS, and SEM revealed that the flame retardant mechanism of the novel TFMB-EP/ TFMB resin primarily results from the presence of trifluoromethyl and biphenyl groups. During combustion, these groups produce non-combustible fluorinated gases, while trifluoromethyl captures free radicals to interrupt the combustion chain reaction and contributes to the formation of a flame-retardant graphitized carbon layer.