Preparation and properties of epoxy resin modified with phosphorus and nitrogen flame retardants

Epoxy resins (EPs) require the addition of flame retardants to extend their application scope. High-efficiency flame retardants typically contain halogens, which can cause tremendous harm to humans and the environment. In this study, we investigated the syntheses of new phosphorus–nitrogen flame retardants (DIT) and flame-retardant EP. DIT is composed of 6-(2,5-dihydroxyphenyl) dibenzo[c,e][1,2] oxaphosphinine 6-oxide, 5-isocyanato-1-(isocyanatomethyl)−1,3,3-trimethylcyclohexane, and tris-(2-hydroxyethyl) isocyanurate. DIT chemical structure was analysed by Fourier-transform infrared spectroscopy. Several formulations of modified epoxy resins (DIT-EPs) were obtained by adding different quantities of DITs. We found that when the flame retardant content reached 25%, the limiting oxygen index of the DIT-EP was 29.0%. This finding expands the application range of EPs.