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

In recent years, the need to use environmentally friendly materials has also triggered increased activity of research and development on water-based formulations for films and coatings. In an effort to meet this goal, waterborne polyurethanes (WBPUs) were developed, which during the coating deposition or the formation of self-standing films release innocuous water to the atmosphere instead of volatile organic compounds (VOCs), as is the case with most traditional solvent-based polymers. One of the most studied applications for this type of materials is water-based paints and coatings. Advances in the development of WBPU have been produced through the careful selection of different sources of hydroxyl group components, as well as different types of chain extenders and emulsifiers. On the other hand, to improve the performance required to the final application composite formulations have been tailored through the addition of organic and inorganic particles/nanoparticles. This review focuses on the relation between formulation-structure and properties of these materials from the initial dispersions to the final coating films. Most commonly used methods of application and their relation to the viscosity of the dispersions have also been briefly considered.