Identification of Oligomers in the Reaction of Polyols with Isocyanates by ¹³C-NMR and GPC

Abstract

Kinetics and mechanism of formation of urethane, biuret, allo-phanate, and isocyanurate in the synthesis of polyurethanes were studied by means of ¹³C-NMR and GPC. In the spectra, the regions of urethane, allophanate, biuret, and isocyanurate were used to study the mechanism of reaction between isocyanates and glycols under different reaction conditions. Urethane groups give signals between 153 and 156 ppm; isocyanurate groups between 149 and 151 ppm. For the determination of secondary rate constants, the well-separated signals of urethane and allophanate in the ¹³C-NMR spectra were used.