Two-component waterborne polyurethane: Curing process study using dynamic in situ IR spectroscopy

The cure reaction of hydroxyl-terminated waterborne polyurethane(HWPU) dispersion and the hydrophilic-modified polyisocyanate to a two component waterborne polyurethane(2K-WPU) in the presence of water environment was monitored by dynamic in situ Fourier transform infrared spectroscopy. With the progress of the reaction, the peak of -NCO group at 2271 cm⁻¹ intensity decreases as a function of reaction time and totally disappears when the reaction is completed, and the hydrogen bond urethane gradually disappears. At different temperatures the reaction rate is different, but there is a great linear fit of the integrated form of the Jander equation versus time. The curing mechanism correspond to Jander equation basically. According to the change of particle size between the HWPU dispersions with 2K-WPU dispersions and the curing mechanism, the curing model was got. The chain of HWPU wrapped hexamethylene diiso-cyanate(HDI) trimer, the product appeared in three-dimensional diffusion and spherically symmetric.