Toughening and strengthening epoxy resin with flame retardant molecular structure based on tyrosine

It is difficult to strengthen and toughen epoxy resin (EP) and concurrently obtain good flame retardancy. A novel flame retardant marked as TFD was prepared by tyrosine (Tyr), furfuraldehyde (FA) and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and co-cured with EP. Only 6 wt% TFD makes EP achieve UL-94 V0 and limited oxygen index (LOI) value 32.4 vol% revealing the high flame retardant efficiency. Furthermore, the tensile and impact strength of EP-8TFD are 29.3 % and 84.4 % higher than that of EP indicating strengthening and toughening effect of TFD. TFD can chemically bond into EP networks via its carboxyl and phenolic hydroxyl reacting with EP leading to good tensile properties. The high rigidity of DOPO forms holes between molecular chains, which eliminates stress concentration and improves impact strength. The strength, toughness and flame retardancy of EP are regulated by simple molecular structure, which provides a good idea for integration of structure and performance.