Mechanism and kinetics of moisture-curing process of reactive hot melt polyurethane adhesive

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.

Keywords

• HMPUR
• Moisture-curing
• Kinetic model
• Diffusion
• Mechanism