Mechanism and kinetics of moisture-curing process of reactive hot melt polyurethane adhesive
Li Sun, Zegang Zong, Weilan Xue, Zuoxiang Zeng
Abstract
Reactive hot melt polyurethane adhesive (HMPUR) was prepared by polycondensation of polyesters, pentaerythritol diacrylate (PEDA) and 4,4′-Methylene diphenyl diisocyanate (MDI). The moisture-curing kinetic experiments for HMPUR film with a thickness of 2.0 mm were carried out at various temperatures (283, 293, 303 and 313 K) and 85% relative humidity, with the mass changes dynamically monitored. A diffusion-reaction assumption was proposed to describe the mechanism of the moisture-curing process, and three kinetic models were established to correlate the moisture-curing kinetic data. The results showed that the model with the first-order reaction assumption is more reasonable. Based on the model, the time-dependent concentration profiles of water in HMPUR film, as well as the depth (x*) of water-diffusion, are predicted. Also, the reaction activation energy (Ek) and the diffusion activation energy (ED) were determined.