Epoxy Resins and Their Hardeners Based on Phosphorus–Nitrogen Compounds

This review examines the fire-retardant properties of compositions that incorporate various classes of phosphorus–nitrogen compounds. Specifically, it focuses on nitrogen-containing derivatives of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phosphinates, phosphorus–nitrogen salts, and aryloxycyclophosphazenes. The findings indicate that these classes of fire retardants enhance the limiting oxygen index, decrease heat and smoke emission indices in epoxy compositions, and facilitate the creation of self-extinguishing materials. Notably, aryloxycyclophosphazenes with reactive functional groups emerge as the most effective fire retardants, particularly in terms of their impact on the mechanical properties of epoxy compositions and compatibility with epoxy resin. This review would be a valuable resource for engineers, chemical engineers, materials scientists, and researchers engaged in the development of non-combustible polymer composites and organoelement compounds.