150 to about 3000 polyisocyanates suitable for use in the present invention include simple polyisocyanates such as hexamethylene diisocyanate 2 4 diisocyanato toluene 2 6 diisocyanato toluene 1 isocyanato 3 3 5 trimethyl 5 isocyanatomethyl cyclohexane 4 4 diisocyanatodiphenyl methane 2 4 u2032 diisocyanatodiphenyl methane or derivatives of these diisocyanates containing biuret or urethane groups isocyanate compounds which can be reacted with a triazole blocking group also include derivatives containing biuret groups include polyisocyanates of the type described in u s pat no 3 124 605 i e mixtures of homologues consisting of tris isocyanatohexyl biuret and higher homologues of this polyisocyanate of the type obtained in the biuretization of hexamethylene diisocyanate these biuret polyisocyanates also have an average nco functionality of from 2 to 4 and an average molecular weight below 10 000 preferably about 150 to about 3000 suitable urethane derivatives or u201c prepolymers u201d of the diisocyanates exemplified above may be used as isocyanate compounds which are reacted with the triazole these urethane derivatives or prepolymers may include the above polyisocyanates as reaction products with less than equivalent quantities of aliphatic diols or triols having molecular weights of from about 62 to about 200 such as ethylene glycol 1 2 or 1 3 propane diol 1 2 butane diol tetramethylene or.