Kinetic analysis of urethane formation between castor oil-based ester polyol and 4,4’-diphenyl methane diisocyanate

Abstract

ABSTRACT Kinetics of urethane formation between castor oil-based ester polyol (COEP) and 4,4′diphenyl methane diisocyanate (MDI) was evaluated using Differential Scanning Calorimeter (DSC) technique. The autocatalytic effect of urethane groups during polyurethane formation was confirmed through this study. DSC runs were made under dynamic heating schedule at various heating rates, viz.: 5, 10, 15 and 20 K/min. Single Heating rates like Chatterjee–Conrad and multiple heating rate method like Ozawa models were used to evaluate the kinetic parameter. Isocyanate index (Eq. of NCO/Eq. of OH) of 1 was used for the reaction between COEP and MDI. DSC thermograms exhibit two isotherms at 70°C and 120°C. Kinetic parameters adopting different models, in terms of activation energy, suggest that the urethane formation occurs grossly in two stages: the first step being standard uncatalysed urethane reaction and the following second step presumably autocatalysed urethane formation. The two exotherms were resolved into two portions. Kinetic analysis was undertaken for the unresolved DSC as well as the resolved ones, treating the resolved thermograms as the outcome of two independent competing reactions.