Synthesis Of DOPO-based Thiazole Derivatives And Their Application In Flame-retarding Epoxy Resin

Epoxy resin has been used widely,due to its outstanding properties,such as good chemical resistance,satisfactory insulation and excellent adhesive properties.However,the inherent flammability of epoxy resin is one of the drawbacks and it is always accompanied with release of lots of smoke during combustion and restricted the applications of epoxy resin.Therefore,it is necessary to reduce its flammability.In this paper,four flame retardants(FRs)namely DOPO-based thiazole/benzothiazole derivatives were successfully synthetized and their applications in epoxy resin were discussed.Firstly,p-hydroxybenzaldehyde(PHB)and 2-aminobenzothiazole(ABZ)or 2-aminothiazole(AZ)were used to synthesize two imine intermediates,then followed by the addition of DOPO,and the obtained compounds were D-P-ABZ and D-P-AZ.D-ABZ and D-AZ were synthesized via Atherton-Todd reaction.The chemical structures of the FRs were characterized by FTIR,1H NMR,31 P NMR and HRESI-MS.Then,to get modified epoxy thermosets,FRs were mixed with epoxy resin using DDM as the curing agent,and then the mixtures were cured in the specified procedure.Secondly,the thermal behaviors,flame retardance,flame-retardant mechanisms,dynamic mechanical analyses and mechanical properties of EP/D-P-ABZ and EP/D-P-AZ were researched,respectively.According to the results,the more addition of the flame retardants,the lower Tg values and the initial decomposition temperatures(Ts%)of EPs,However,the flame retardance was improved greatly,and total heat release(THR)and total smoke release(TSR)were reduced,which was of great help to provide a greater possibility for people to escape from the fire hazard.Based on the analyses of TG,cone calorimeter,TG-FTIR and Py-GC/MS,it was deduced that both D-P-ABZ and D-P-AZ exerted their flame-retardant effect not only in the gaseous phase,but also the condensed phase.Finally,the effect of D-ABZ and D-AZ on epoxy resin were also investigated.The results showed that the flame retardants could reduced combustion performance greatly.Meanwhile,the cured epoxy resins also possessed outstanding mechanical properties with comparison to neat epoxy resin,EP/D-ABZ and EP/D-AZ,which showed high promise for application.According to the relevant tests,it was speculated that D-ABZ predominantly exerted gaseous-phase activity,while D-AZ acted both in the vapor and condensed phase.