Newcastle University engineers have invented a new glue that they believe promises to change how we recycle. The glue’s reversible nature means it can be used for myriad purposes, but specifically for adhering labels to plastic bottles. The labels will be able to be efficiently detached, making them easier to recycle. 

The reversible glue, developed by experts from Newcastle University’s School of Engineering, is a water-based emulsion that bonds together and can be separated by water. The glue uses polymers that contain an electrical charge to keep the emulsion stable and to stick to different surfaces. When a surface coated with a positively charged emulsion is joined to a surface coated with a negatively charged one, the two components stick together. However, if the bond is immersed in water that is either slightly acidic or alkaline, it fails and the label is easily removed, creating new opportunities for recycling.

First author of the paper, Dr Adriana Sierra-Romero, research associate at the School of Engineering, said, “We have been working with waste management company, Biffa, and we have shown that with our glue, a propylene label stuck to a PET bottle can be removed by the wash water in their recycling plant. Although the bottles can be recycled, these labels are usually sent to landfill, so we know our technology can really make a difference. There will be many other industries where our glue can be used, and we look forward to working with other companies.”

The glue is based on current industrial paint making processes and is developed from cheap materials so it can be scaled up easily. Because it is water-based it does not have the volatile organic solvents used in many commercial glues, but unlike other water-based adhesives, exposure to humid environments does not cause bond failure. The team has shown that its shelf life at room temperature is at least a year.

Published in the leading chemistry journal, Angewandte Chemie, International Edition, the work was funded by the Engineering and Physical Sciences Research Council (EPSRC). The team has recently been informed that the EPSRC will fund the research for another three years, bringing total funding for the team to £1M.

Dr. Katarina Novakovic, reader in Polymer Engineering and co-investigator on the project said, “Companies are making more and more ambitious net-zero targets. Our glue will help them achieve these. Newcastle University has a great record in sustainability. It is embedded in our curricula, for example, I am involved in teaching our undergraduate students about bottle recycling and they really enjoy this real-life example. It is great that we have a glue that can improve industrial processes in these areas.”

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