The machinery at municipal recycling facilities often gets jammed up with the adhesives which are utilized on items such as jar labels and cardboard boxes. That may cease to be the case in the not-too-distant future, however, thanks to a new degradable adhesive.
Along with gumming up the works at recycling plants, adhesive waste can also clog the facilities' water systems and even make its way into what end up being lower-quality recycled materials. And while other degradable adhesives do already exist, most of them lack the sticking strength of their conventional counterparts.
In an effort to address these problems, a University of Surrey team led by Prof. Joseph Keddie has developed an experimental new degradable adhesive which is described as being "very similar to that used on commercial packaging tape." Its key ingredient is a chemical additive known as thionolactone, which makes up just 0.25% of its composition.
"Adhesives are made from a network of chain-like polymer molecules, irreversibly linked together, which leads to the residue build-up we see left behind when recycling materials such as glass and cardboard," said Keddie. "Our additive creates what we call degradable thioester connections in the polymer network, and provides an innovative solution to making recycling processes residue-free."
The connections are completely degraded via the simple processes of either aminolysis (a chemical reaction with ammonia) or thiolysis (a reaction with a molecule called coenzyme A). In lab tests incorporating substrate materials such as glass, steel, plastic and paper, labels utilizing the new adhesive could be detached up to 10 times faster than those using a traditional adhesive.
Keddie and colleagues are now investigating the commercial viability of the adhesive, along with its environmental sustainability. A paper on their research was recently published in the journal Angewandte Chemie.
Source: University of Surrey
