A monomolecular intumescent flame retardant for improvement simultaneously of fire safety, smoke suppression, and mechanical properties of epoxy resin

In this article, a monomolecular intumescent flame retardant 1,4-bis (diethyl methylenephosphonate) piperazine defined as BDEMPP was introduced into epoxy resins (EP) thermosets. The fire safety, combustion behavior, thermal properties, mechanical performance, transparency, and flame-retardant mechanism of EP/BDEMPP thermoset were investigated systematically. The EP thermosets passed UL-94 V-1 level with the limit oxygen index value of 28.3%, and the release of heat and smoke were inhibited when 9 wt% BDEMPP was added. Moreover, the tensile strength and modulus, flexural strength and modulus, charpy impact strength of EP/9 wt% BDEMPP were increased by 15.0%, 22.4%, 15.4%, 15.6%, and 22.6% in comparison of pure EP thermosets, respectively. EP/BDEMPP composites possessed good transparency and the transmittance of EP/9 wt% BDEMPP was 87.1% at 600 nm UV irradiation. The investigation of flame retardant mechanisms demonstrated BDEMPP exerted flame retardant effect both in gaseous and condensed phase. BDEMPP exhibited good compatibility, flame retardancy, smoke suppression, and mechanical enhancement for EP thermosets.