NEW PHOSPHACYCLIC MOLECULES AND THEIR APPLICATION AS FLAME RETARDANTS FOR EPOXY RESINS

9,10-Dihydro-9,10-oxa-10-phosphaphenanthrene-10-oxide (DOPO) has been commercialized as a gas phase active flame retardant. Its P-H bond allows its reactive incorporation into epoxy resins and formation of new additives via Michael-like addition. To better understand of the role of radicals in the flame retardant mechanism, 9,10-dihydro-9-aza-10-phosphaphenanthrene-10-oxide (DAPO) and 9,10-dihydro-9,10-oxa-10-phosphaphenanthrene-10-sulfide (DOPS) were synthesized. DAPO was found to undergo unprecedented tautomerism for a P(V) cycle. The detailed synthetic approach and spectroscopic characterization of DAPO and the flame retardant behavior of DAPO and DOPS will be discussed.