Evaluation of the crosslinking reaction kinetics of cationic polyol dispersions with differential scanning calorimetry and dielectric analysis

The crosslinking reaction kinetics of two-component waterborne polyurethanes (2K-WPUs) composed of cationic polyol dispersions and hydrophilically modified hexamethylene diisocyanate (HDI) tripolymer were investigated by differential scanning calorimetry (DSC) and dielectric analysis (DEA) techniques. DSC data fit for the 2K-WPUs was carried out with Málek's mechanism function method. The kinetic parameters and kinetic models of crosslinking reaction were determined by the kinetic analysis with Málek's method. The result showed that the crosslinking process of the reaction followed an autocatalytic reaction. Sestak–Berggren model (S–B model) could favorably describe the crosslinking reaction process of the studied 2K-WPUs. The reaction rate curves derived from the experimental data showed a good agreement with the theoretical calculation under 5–20 °C min−1 heating rate. Isothermal DSC and DEA of the crosslinking process of the 2K-WPUs were used to confirm the obtained kinetics equations. The conversion–time curves from isothermal DSC matched favorably with the calculated curves from the obtained kinetic equations, and the log ion viscosity–time curves from isothermal DEA matched roughly with the conversion–time curves from DSC.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Kinetic model of the bulk crosslinking reaction of 2K-WPUs is investigated. ► Freeze-drying and DSC are introduced to study the kinetics. ► S–B model from the Málek method well describes the crosslinking reaction of 2K-WPUs. ► DEA is used to confirm the obtained kinetics equations.