Abstract: Ethylenically unsaturated monomer solutions containing ethylenically unsaturated polyisocyanurate resins are thickened to moldable non-sticky gels by the formation in said solution of minor amounts of cross-linked polyurethane resin mixtures. These are made by the addition of polyisocyanates and certain low molecular weight polyols and urethane formation catalysts. When these moldable gels are fully cured, their physical properties are nearly equal to those cast from the ungelled polyisocyanurate monomer copolymer.

Abstract: Esters of tetracarboxylic acids having the following general formula:(RO.sub.2 C').sub.2 .dbd.X.dbd.(C"O.sub.2 R').sub.2wherein .dbd.X.dbd. is selected from tetravalent 5 or 6 membered or a double 6 membered ring system and wherein C' and C" carbons are attached to separate pairs of vicinal carbons and R and R' are selected from halogenated organic radicals containing a least 2 atoms of chlorine or bromine and the other of each R and R' is selected from --H, --CH.sub.2 CH(OH)CH.sub.2 O.sub.2 CCR".dbd.CH.sub.2, and --CH[CH.sub.2 (OH)]CH.sub.2 O.sub.2 CCR".dbd.CH.sub.2 are useful in the preparations of high molecular weight polymers and copolymers which are improved in fire retardance and strength.