Multidimensional Analysis of Polyurethane Film Formation Behavior Using Complementary Rheological, Dielectric, and Calorimetric Methods

Polyurethane was formulated with the acrylic polyol and HDI trimer, with and without DBTL. A range of characterisation techniques, DSC, rheology, and DEA, were employed to monitor the reaction, and the results were compared. The findings indicated that each technique yielded informative results; however, these results require confirmation by other methods. In essence, all techniques demonstrated a consistent trend with respect to reaction rate and curing behaviour. As the curing time increased, Tg exhibited a shift toward higher temperatures. A significant difference in the reaction rate was observed when DBTL was used. However, because Tg is sensitive to molecular weight and polymer structure, this technique is better used as a confirmatory method. Similar acceleration in reaction rate and curing was observed in both DEA and rheology measurements. The catalysed sample exhibited a faster and more consistent reaction rate than the non-catalysed sample. The rheological measurements demonstrated the presence of two different slopes in the acceleration of viscosity under isothermal conditions. These may be attributed to the formation of a three-dimensional polymeric network. In the catalysed sample, this effect may have been suppressed or masked because of the accelerated reaction rate. The rheological measurements, which involve the viscosity-time profile, provided enhanced insight into the reaction rate. In contrast, DEA exhibited greater sensitivity in detecting changes in the curing behaviour. These results demonstrate that selecting and comparing the most suitable techniques is important for saving both time and cost.