Thermosetting polyester resins can be formulated over a wide range of compositions to provide a broader selection of resin properties than those available with anhydride flame retardant. Resins formulated with it have high chemical and flame resistance minimal thermal discoloration and excellent light stability The high bromine content of it and its ready reaction into polyurethanes make it suitable for use in rigid polyurethane foams, UPE,PU rigid foams.