Synergistic effects of nonstoichiometric p,n-flame retardants based on melamine and ammonium derivatives of phosphoric acid. Part 1. Literature review

A review of current research in the development of synergistic flame retardants based on phosphorus- and nitrogen-containing compounds, including melamine, ammonium polyphosphate (APP), DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivatives and hybrid systems is presented. The mechanisms of their action, such as the gas-phase inhibition of radicals, the formation of thermostable carbon layers and the catalytic degradation of polymer matrices have been considered. Special attention was paid to combinations demonstrating synergy, for example, phosphorus-nitrogen-carbon (P-N-C) systems, nanomaterials (graphene, nanotubes) and organometallic frameworks (MOF). It is shown that such compounds significantly increase the fire resistance of polymers (oxygen index up to 45%, UL-94 rating V-0), reduce heat generation and smoke generation, while maintaining mechanical properties. The environmental advantages of halogen-free flame retardants and the prospects for their use in epoxy resins, polyurethanes, textiles and composites are discussed.