Solving a sticky problem in recycling

Scientists from the University of Surrey have developed a dissolvable adhesive to prevent sticky residue left on recyclable materials such as glass and cardboard.

Sticky residue causes problems in the recycling industry, ranging from low-quality products, blocked water systems and even damaged recycling machinery.

The newly invented adhesive is similar to that used on commercial packaging tape and contains 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 also be detached up to 10 times faster when compared to a non-degradable adhesive.

Professor Joseph Keddie, Leader of the Soft Matter Physics laboratory at the University of Surrey and fellow of the Surrey Institute for Sustainability, said adhesives are made from a network of chain-like polymer molecules which are linked together. These create the residue build-up left behind when recycling materials such as glass and cardboard. Residues have consequences on an industrial scale, compromising the quality of recycled products.

The additive creates degradable thioester connections in the polymer network and provides a solution to making recycling processes residue free.

Peter Roth, Senior Lecturer of Polymer Chemistry at the University of Surrey, and fellow of the Surrey Institute for Sustainability, said there are existing degradable adhesives on the market, but they are not similar to what is currently used industry-wide in their chemical make-up.

The researchers are aiming to prove that it is possible to use similar adhesives and show that a simple additive can help increase the quality of recycled materials. The next step is to look at the commercial viability of the additive, as well as the sustainability impact.

The adhesive has been tested on glass, steel, plastic and paper, including cardboard.

“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,” said Rohani Abu Bakar, a PhD student working on the project.

The paper has been published in the German Chemical Society journal Angewandte Chemie.

Image credit: University of Surrey