Remotely triggered reversible bonds in adhesives for sustainable multi-layered packaging

Abstract

Plastic films used in food packaging are multi-layered materials comprising different polymer layers each with a specific function, which makes the packaging very difficult to recycle, ending up in landfills or incineration plants. Innovative approaches are required to resolve this issue and this work focuses on the adhesive layers used to bind the polymer layers together. We report on the development of a new, reusable polyurethane adhesive containing dynamic covalent Diels-Alder bonds that can be reversibly opened and closed by controlling the temperature. The breaking/formation cycle of the thermoreversible bonds in the adhesive can be repeated up to ∼20 times. In addition, the incorporation of radiation-absorbing nanoparticles into the adhesive facilitates bond breaking that can be remotely triggered in tens of seconds using NIR radiation. This new adhesive concept will facilitate the recycling of the individual polymer layers, opening the door to a circular economy solution towards sustainable packaging.