The phase mixing of moisture cured polyurethane-urea during cure

Moisture cured polyurethane-ureas (MCPUs) is one of the industrially important polymer, which shows good thermal-mechanical and weathering properties and widely used in the reactive hot melt adhesives and coatings. In this study, chemically crosslinked MCPUs were prepared by reacting isophorone diisocyanate (IPDI) with polyethers like polytetramethyleneglycol (PTMG)-1000 and polyethyleneglycol (PEG)-1000, with NCO/OH ratio 1.6:1. Trimethylol propane (TMP) was used as a crosslinking agent during the prepolymer synthesis. The excess isocyanate of the prepolymers was cured with moisture at 25 degrees C and humidity of 40%. Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical thermal analyzer (DMTA) measurements were used to monitor curing process of polyurethane-urea systems. Higher correlation coefficient (R-2) values were obtained for the second-order cure model compared to the first- and third-order for both the synthesized prepolymers. [GRAPHICS] The change in short range ordering associated with hydrogen bonding as well as decrease in crystallinity of soft segment during the phase mixing was observed from differential scanning calorimetry (DSC) measurements. The change in thermal stability was assessed by thermogravimetric (TG) analysis. Characterizations of the curing process provide an essential base to obtain best polymer. The phase mixing phenomenon was confirmed from the angle resolved X-ray photoelectron spectroscopy (AR-XPS). (c) 2005 Elsevier B.V. All rights reserved.