Enhancement of smoke and toxic gas suppression during combustion and improvement of the mechanical properties of epoxy resin by incorporation of a modified MOF material containing the phosphoheterophene group†

To reduce the adverse effects of the flammability of epoxy resin (EP), addition of flame-retardants in EP is a common and effective strategy. A 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) derivative, DOPI, has been synthesized by adding the double bond of itaconic acid (ITA) to DOPO, and was utilized for ligand exchange with terephthalic acid in MIL-53(Fe) to obtain the derived material of MIL-53(Fe)-DOPI. A series of blends were prepared by adding different proportions of MIL-53(Fe)-DOPI into EP. The fire resistance and mechanical properties of these blends were assessed. Among them, the 2 wt% MIL-53(Fe)-DOPI/EP blend displays a UL-94 V-1 rating and a limiting oxygen index (LOI) of 30.0% for combustion. The peak smoke production rate (p-SPR), peak CO production rate (p-COP) and peak HRR production rate (p-HRR) for combustion are respectively reduced by 26.56%, 41.2% and 39.9% compared to the same parameters for the combustion of pure EP. Based on the analysis of Py-GCMS, TG-FTIR, Raman and FE-SEM, a flame retardancy process has been proposed. Additionally, the tensile strength, flexural strength, flexural modulus and impact strength of a blend containing 3 wt% MIL-53(Fe)-DOPI in EP are respectively increased by 24.3%, 62.0%, 85.2% and 13.8% relative to those for unmodified EP. Therefore, MIL-53(Fe)-DOPI is an outstanding additive that can effectively reduce the formation of the smoke and toxic gas during combustion, at the same time, improving the mechanical properties of EP.