Formulation, structure and properties of waterborne polyurethane coatings: a brief review

Abstract

In recent years, the need to use environmentally friendly materialshas also triggered increased activity of research and developmenton water-based formulations for films and coatings. In an effort tomeet this goal, waterborne polyurethanes (WBPUs) were developed,which during the coating deposition or the formation ofself-standing films release innocuous water to the atmosphereinstead of volatile organic compounds (VOCs), as is the case withmost traditional solvent-based polymers. One of the most studiedapplications for this type of materials is water-based paints andcoatings. Advances in the development of WBPU have been producedthrough the careful selection of different sources ofhydroxyl group components, as well as different types of chainextenders and emulsifiers. On the other hand, to improve the performancerequired to the final application composite formulationshave been tailored through the addition of organic and inorganicparticles/nanoparticles. This review focuses on the relationbetween formulation-structure and properties of these materialsfrom the initial dispersions to the final coating films. Most commonlyused methods of application and their relation to theviscosity of the dispersions have also been briefly considered.