Waterborne Polyurethane Dispersions Obtained by the Acetone Process: A Study of Colloidal Features
Résumé
Waterborne polyurethane (PU) dispersions were prepared from isophorone diisocyanate (IPDI), 2-bis(hydroxymethyl) propionic acid (DMPA), 1,4-butane diol (BD), poly(propylene glycol) (PPG), and triethylamine (TEA) by means of phase inversion through the acetone process. Changes in DMPA content, initial PU content in acetone, phase-inversion temperature, evaporation conditions, and solvent nature were found to have a great impact on dispersion properties. Using a DMPA concentration of 0.30 mmol/g(pol), stable PU dispersions could only be obtained when the initial PU content in acetone was at least 60 wt %, and phase-inversion temperature was lower than 30 degrees C. However, when increasing the PU content to 75 wt %, stable dispersions were obtained using DMPA concentrations three times lower. Finally, viscosity curves during the water addition step as well as a phase diagram were determined to understand the particle formation mechanism.