Plastic bottles easier to recycle with new degradable glue

A new type of adhesive that can be cleanly removed from plastic bottles and packaging before disposal could lead to better-quality recycled plastic, a new study has shown.  

The adhesives used to stick labels onto plastic bottles and packaging often leave behind a detrimental residue that limits how the plastic can be recycled and reused.  

A research team from the Department of Chemistry at the University of Reading has created a new polymer adhesive that breaks down when treated with basic or alkaline solutions. This means labels can stay firmly stuck to bottles during normal use but can be easily removed as part of the recycling process.  

Matthew Hyder, lead author of the research, said: “Existing commercial adhesives can prove extremely difficult to remove from plastic surfaces because of their chemical composition. Our new polymer adhesive has been designed so that it can be removed from a plastic surface when exposed to basic or alkaline solutions. By making labels that can be removed completely, we are helping improve the quality of recycled plastic and usefulness in its next life."   

Multiple uses 

Published last month in the journal Macromolecules, the study describes how researchers designed and generated a polyurethane that incorporated sulfonyl ethyl urethane units, which act as a chemical switch when exposed to certain substances. In tests, treating the polymer adhesive with basic or alkaline solutions triggered this switch, making it lose up to 65% of its sticking power on a range of surfaces.   

During everyday use, these adhesives have the potential to work just as well as current commercial alternatives. When tested, they proved strong enough at different temperatures on both glass and aluminium surfaces, making them suitable for everything from food containers to shipping packages to electronic appliances.  

This development, sponsored by Domino Printing Sciences PLC in conjunction with the University of Reading, could transform how waste is handled across many industries. By making it easier to separate different materials during recycling, the quality of recycled materials could significantly improve, reducing the amount of waste that ends up in landfill.