Comparative study on curing kinetics of MDI-based polyurethanes with different chain length diol curing agents

Abstract

The difference in the reaction between thermosetting polyurethane (CPU) and binary alcohol system curing agents is crucial for obtaining accurate curing kinetics models and selecting curing agents. Based on a systematic comparison of the reaction activation energies and kinetic models of three different chain length fatty alcohol curing agents, ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, the effect of curing agent chain length on the curing reaction was elucidated. Using differential and integral transformation methods to process non-isothermal DSC tests results, the effect of different chain lengths curing agents on the activation energy of MDI based polyurethane were analyzed. Based on the self-catalytic model, the segmented curing mechanism of the MDI based polyurethane systems were studied, and applicable high-precision segmented kinetic models’ parameters were calibrated. The optimal curing conditions for these systems were determined using extrapolation. The research results indicate that when the curing degree increases to 95 %, the overall activation energy of the MDI/1,4-butanediol system decreases by 47.1 %, accompanied by a faster self-catalytic. However, the activation energies of the other two systems, MDI/propylene glycol system and MDI/1,6-hexanediol system increased by 62. % and 295.0 %, respectively. This slows down the reaction rate of the two systems, which was 7.8 % and 10.9 % slower than the MDI/1,4 butanediol. heir molecular cross-linking network limits the diffusion ability of their chains and reduces the self-catalysis, resulting in slow reactions. These results will provide theoretical guidance and reference for the material formulation, process optimization of MDI based polyurethane actual curing production.