Recyclable, remendable and healing polyurethane/acrylic coatings from UV curable waterborne dispersions containing Diels-Alder moieties

The aim of the present work is to increase the sustainability of UV curable waterborne polyurethane dispersions using the Diels-Alder chemistry. In this way, the obtaining of crosslinked polyurethane coatings presenting healing and recycling properties is proposed. Thus, waterborne polyurethanes were obtained by the acetone process replacing the chain extender by a diol containing the Diels Alder adduct and using acrylic chain ends that allowed the UV cross-linking. Photo-DSC results showed that the Diels Alder adduct did not prevent the UV cross-linking of the coating. In addition, FTIR, DSC and rheological experiments confirmed the occurrence of the DA and retro DA reaction (at 60 degrees C and 120 degrees C respectively) in the cross-linked polymer. Thanks to this reaction, the materials obtained by this methodology could be healed and reprocessed when increasing the temperature as shown by the maintenance of the mechanical properties and carbon dioxide permeability after repairing. These results can be of great interest towards the development of more sustainable waterborne polyurethane coatings.