polyacid anhydride sulfur oxide or phosphorus oxide the process of heating the resin so as to cause reversible crosslinking is also disclosed application_number US 79951504 A description the resins are cured under conditions other than radiation the resultant resins exhibit thermoset crosslinked behavior at low temperatures but thermoplastic behavior at elevated temperatures due to breaking of the ionic crosslinks that are formed this phenomenon is very useful in allowing unused resin to be recycled suitable metals include lithium sodium potassium cesium magnesium calcium strontium barium titanium zirconium vanadium chromium molybdenum tungsten manganese iron cobalt nickel palladium copper zinc cadmium mercury boron aluminum gallium indium silicon germanium tin lead antimony bismuth and the like the metal compound can be for example the oxide halide alkoxide hydroxide nitrate sulfate carboxylate and carbonate the most preferred metal compound is zinc oxide since it reacts very easily and is readily available suitable anhydrides and dicarboxylic acids include phthalic acid trimellitic anhydride which contains one anhydride and one carboxyl group pyromellitic anhydride 5 norbornene endo 2 3 dicarboxylic anhydride naphthyl anhydride naphthalene tetracarboxylic acid dianhydride maleic anhydride succinic anhydride chlorendic anhydride maleic acid succinic acid fumaric acid oxalic acid malonic acid glutaric acid adipic acid dimer fatty acids and styrene maleic anhydride polymers the alpha beta ethylenically unsaturated hydroxy compound is preferably selected among alpha beta ethylenically unsaturated hydroxy derivatives of polyols more preferably of diols more preferably these ethylenically.