Characteristics of Dispersible Polyurethane Powders for Waterborne Systems

摘要

Powders of polyurethanes (PU) dispersible in water were prepared and the rheological properties of waterborne PU prepared by the dispersion of PU powder and colloidal nano silica were investigated. Viscosity of the waterborne PU based on the dispersible powders increased with increasing the concentration of PU powders. The viscosity increase could be lowered by the incorporation of the colloidal nano silica and was attributed to Farris effect of colloidal systems. Adhesive strength of the waterborne PU based on the dispersible PU powders was similar to those of waterborne PU before drying process to prepare dispersible PU powders. Thermal transition temperatures were not affected by the colloidal nano silica incorporated. It is postulated that the dispersible PU powders can have advantage of fast drying by increasing the solid content in the dispersion systems and long storage life compared with the waterborne PU.