New crosslinking method for waterborne polyurethane

A new study proposes a novel strategy of crosslinking for waterborne polyurethane using dibromide as a crosslinker and 1,1,3,3-tetramethylguanidine (TMG) as an esterification promotor.

Waterborne polyurethane (WPU) is an environmentally benign material with excellent performance and wide use. However, due to its inherent hydrophilic groups, such as carboxyl, the waterproof and mechanical properties of its corresponding films have been seriously affected. To address this dilemma, researchers have now proposed a new crosslinking method by using commercialized dibromide as a crosslinker and 1,1,3,3-tetramethylguanidine (TMG) as an esterification promoter, to make the carboxyl groups of waterborne polyurethane and dibromide undergo esterification crosslinking reaction, which reduces the content of carboxyl groups while realising the crosslinking of WPU films.

The results show that the water absorption of WPU films crosslinked by this method is greatly reduced, the hydrophobic property (contact angle) is significantly improved, and the mechanical properties are greatly enhanced. Meanwhile, to facilitate construction and commercial application, the reseachers have designed a two-component WPU coating, and their corresponding films also show great hydrophobic and mechanical properties. As they point out: the crosslinking method has the advantages of low cost, simple operation, high crosslinking efficiency and mild reaction conditions.

The review has been published in Progress in Organic Coatings, Volume 181, August 2023.

Event tip

Water-based systems are also the focus of the EC Conference Bio-based and Water-based Coatings on November 14 and 15 in Berlin, Germany. At the conference you will learn about the latest developments in bio-based and water-based coatings.