Hexaacrylated cyclophosphazene (HACP) and its cured powder were blended with a commercial epoxy acrylate, EB600, to obtain UV-curable flame-retardant resins. The flame retardancy and the thermal stability of their cured films at elevated temperature were found to be improved from the measurements of limiting oxygen index and thermogravimetric analysis. Photopolymerization kinetics study showed that the photopolymerization rate increased with increasing amounts of HACP in EB600, whereas the unsaturation conversion decreased conversely. Dynamic mechanical thermal and mechanical properties showed that the addition of HACP had no influence, whereas adding HACP powder to EB600 had a negative effect, thus limiting its application in UV formulations. (C) 2005 Wiley Periodicals, Inc.