Structural Stability of Isocyanurate Polyisocyanate

Abstract

The structural stability of isocyanurate polyisocyanate, derived from hexamethylene diisocyanate, was studied by semi-empirical molecular orbital calculation using PM3 program of MOPAC 6.0 and thermal analysis; the results were compared to those for adduct polyisocyanate and biuret polyisocyanate. The calculated values of heat of formation (ΔH) in elimination of hexamethylene diisocyanate from corresponding polyisocyanate were as follows: isocyanurate, adduct, and biuret polyisocyanate: 39.5, 17.2, and 20.3 kcal/mol, respectively. The calculated values of activation energy (ΔE) 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, respectively. The tendency of thermal stability of each polyisocyanate observed by thermogravimetric analysis, was the same as the order of values of activation energy of the above elimination reaction. Structural stability of isocyanurate polyisocyanate was quantitatively shown by the values of activation energy in the elimination of butyl isocyanate from each polyisocyanate model.