Effect of a novel P/N/S-containing reactive flame retardant on curing behavior, thermal and flame-retardant properties of epoxy resin

•A novel co-curing and flame retardant agent (DHBAZ) was synthesized and exerted excellent flame retardance in epoxy resin.•DHBAZ as a reactive flame retardant contains phosphorus, nitrogen and sulfur.•DHBAZ shows positive efficiency on inhibiting heat release and smoke production of epoxy resin.•EP/DHBAZ with a similar Tg to EP shows an increased storage modulus.•The possible flame retardant mechanism of DHBAZ is speculated according to the analyses of TG-FTIR and py-GC/MS.

A novel P/N/S-containing flame retardant DHBAZ was synthesized with 9, 10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, p-hydroxybenzaldehyde and 2-aminothiazole, and used as a co-curing agent for epoxy resin (EP). With the aid of DHBAZ, EP/7.5% DHBAZ passed UL-94 V-0 rating, and owned a LOI value of 31.4%. Besides, DHBAZ also played a positive role in inhibiting the release of heat and the production of smoke. Through non-isothermal DSC tests it revealed that in the presence of DHBAZ, epoxy resin was cured at a lower temperature and showed lower curing-reaction activity energy. DMA analyses indicated that EP/7.5% DHBAZ showed an increased storage modulus, and it had a close glass transition temperature with EP. While, DHBAZ presented a decreased effect on the thermal stability of epoxy resin acquired from TG analyses. Finally, the flame-retardant mechanism studied by TG-FTIR and py-GC/MS deduced that DHBAZ worked in the gaseous phase by producing P, PO and incombustible gases.