Plant oil-based waterborne polyurethanes: A brief review

Abstract

The increasing pressure from consumers and policy makers to reduce the use of synthetic polymers, whose production contributes to the depletion of non-renewable resources and are usually non-biodegradable, has prompted the efforts to find suitable bio-based sources for the production of polymers. Vegetable oils have been a frequently spotted in this search because they are versatile, highly available and a low cost liquid biosource, which can be used in the synthesis of a wide plethora of different polymers and reactive monomers. Following the same idea of reducing the environmental stress, the traditional polyurethanes that are soluble in organic solvents have been targeted for replacement, particu-larly in applications such as adhesives and coatings, in which the solvent is released to the atmosphere increasing the air pollution. Instead, waterborne poly-urethanes (WBPU), which are polyurethane dispersions (PUD) prepared in aqueous media, release benign water to the atmosphere during use as supported or self-standing films for different applications. In this brief review, the contributions to the development of WBPUs based on vegetable oils are discussed, focusing mainly on the contributions of the last decade. The synthesis of ionic and non-ionic PUDs, their characterization and the properties of the resulting dried mate-rials, as well as derived composite materials are considered.