Synthesis and formulation of novel phosphorylated dame retardant curatives for thermoset resins

More than 20 novel phosphorylated monomers have been prepared. General synthetic targets were of the form: Di/tri amino cyclotriphosphazenes, Di/tri hydroxy cyclotriphosphazenes, Phosphine oxide derivatives. These dual-function materials act both as flame retardants and as curatives. Ease and cost of synthesis were taken into account in choosing promising candidates for further study. Limited formulation was then performed in epoxy resin systems to determine flammability and thermomechanical properties, and also the efficiency of these flame retardant materials as curatives. Two curatives, based upon phosphine oxide and phosphazene chemistries, were scaled up to more than 10 kg, and were evaluated in a range of thermoset resin systems. Flammability characterisation was carried out using OSU (Ohio State University) and cone calorimeters to measure ignitability, heat release rate, smoke and toxic gas production. Screening of thermal and mechanical properties was also performed. Three formulations showed promising overall properties: toughened phosphine oxide based epoxy, untoughened phosphine oxide based bismaleimide resin, toughened phosphazene based epoxy, and these were selected for further work with composite materials. (C) 1996 Published by Elsevier Science Limited