Adhesive residue left on recyclable materials causes problems in the recycling process, including low-quality products, blocked water systems, and damaged machinery. A new adhesive, invented by researchers at the University of Surrey, aims to alleviate these problems. The adhesive, similar to commercial packaging tape, has a chemical additive known as thionolactone, which makes up 0.25% of the composition. This additive allows the adhesive to be dissolved in the recycling process. Labels can be detached up to 10 times faster when compared to a non-degradable adhesive. 

"Adhesives are made from a network of chain-like polymer molecules, irreversibly linked together, which leads to residue build-up we see left behind when recycling materials such as glass and cardboard,” said Professor Joseph Keddie, leader of the Soft Matter Physics laboratory at the University of Surrey and fellow of the Surrey Institute for Sustainability.

"The problem of network residues is frustrating on an industrial scale and consequences of insoluble adhesives on the quality of recycled products are of even greater concern. Our solution offers the promise of less challenging and more cost-effective recycling. Our additive creates what we call degradable thioester connections in the polymer network and provides an innovative solution to making recycling processes residue free." 

Dr. Peter Roth, senior lecturer of Polymer Chemistry, University of Surrey, and fellow at the Surrey Institute for Sustainability said, "While other degradable adhesives exist, there are none which resemble what is currently used industry-wide in their chemical make-up. We are proving it is possible to use similar adhesives and show that a simple additive has the potential to increase the quality of recycled materials such as glass and cardboard. 

Rohani Abu Bakar is the lead Ph.D. student working on the project, funded by the Malaysian Rubber Board. Commenting on the impact this will have when she returns to Malaysia, she said, "The interdisciplinary approach across chemistry and physics has been incredibly useful in building the knowledge and skills to solve a very real sustainability problem. There is no doubt that many countries across the world need to review how they recycle major materials, and this brings us one step closer to reaching our sustainability goals on an industrial scale." 

To learn more, visit www.surrey.ac.uk. 

To see the research, visit www.onlinelibrary.wiley.com.