STRUCTURAL STABILITY OF ISOCYANURATE POLYISOCYANATE

The structural stability of isocyanurate polyisocyanate, derived from hexamethylene diisocyanate, was studied by semi-empirical molecular or bital calculation using PM3 program of MOPAC 6.0 and thermal analysis; the results were compared to those for adduct polyisocyanate and biur et polyisocyanate. The calculated values of heat of formation (Delta H ) in elimination of hexamethylene diisocyanate from corresponding poly isocyanate were as follows: isocyanurate, adduct, and biuret polyisocy anate: 39.5, 17.2, and 20.3 kcal/mol, respectively. The calculated val ues of activation energy (Delta E) in elimination of butyl isocyanate from corresponding polyisocyanate models were as follows: isocyanurate , adduct, and biuret polyisocyanate: 66.5, 58.5, and 51.6 kcal/mol, re spectively. The tendency of thermal stability of each polyisocyanate o bserved by thermogravimetric analysis, was the same as the order of va lues of activation energy of the above elimination reaction. Structura l stability of isocyanurate polyisocyanate was quantitatively shown by the values of activation energy in the elimination of butyl isocyanat e from each polyisocyanate model.