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

Abstract

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 3.5 wt% DiDOPO/3.5 wt% 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.