Enhanced flame retardancy of epoxy resin containing a phenethyl-bridged DOPO derivative/montmorillonite compound

A phenethyl-bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative (DiDOPO) was combined with organically modified montmorillonite and incorporated into an epoxy resin to improve its flame retardancy. When only 3.5wt% DiDOPO/3.5wt% organically modified montmorillonite was introduced into epoxy resin, the limited oxygen index rose from 21.8% to 32.2% and achieved a V-0 rating in the UL 94 test. The decomposition and pyrolysis products in the gaseous phase were characterized by thermogravimetry-Fourier transform infrared spectroscopy. The increase in char yield was restricted due to the incorporation of organically modified montmorillonite. Moreover, a large amount of phosphorus was released into the gaseous phase. The evaluation of flame retardancy, based on cone calorimeter data, testified that organically modified montmorillonite improved the protective-barrier effect of the fire due to the epoxy resin/DiDOPO/organically modified montmorillonite residue, which was also proved from the digital photographs and scanning electron microscopy results. Combination of the protective-barrier effect of organically modified montmorillonite and the flame-inhibition effect of DiDOPO exerted a superior flame-retardancy effect, resulting in good performance of epoxy resin/DiDOPO/organically modified montmorillonite flame-retardant. Overall, organically modified montmorillonite was an efficient adjuvant for the flame-retardant epoxy resin/DiDOPO system.