Scientists have unveiled a new chemical upcycling technique aimed at improving the degradability of existing plastics, as efforts intensify to develop more sustainable alternatives to landfill and incineration.
Applying this new process to upcycle existing plastics – such as those used for food packaging and in 3D printing – could contribute to tackling global plastic pollution issues.
Some 99 per cent of plastics in circulation are not biodegradable, and the eco-friendly alternatives that do exist often break down slowly or require high temperatures and harsh chemicals, as the group explains.
Researchers at the University of Edinburgh and RPTU University Kaiserslautern-Landau, Germany, have led the development of a new method of producing a type of plastic – known as a polythionoester – that is more readily degradable.
The biodegradable material is produced by altering the chemical structure of an existing plastic, removing some atoms of oxygen chemically bonded to carbon and replacing them with sulfur atoms. A molecule capable of installing sulfur in this way – known as a thionating agent – is applied in a simple one-step process to achieve this transformation.
Long polythionoester molecules are built from carbon-sulfur bonds that are much weaker than the carbon-oxygen ones in the original plastic, unlocking different physical properties while also making them significantly easier to break down, the team reports.
Researchers trialled the new method on an existing type of biodegradable plastic – polycaprolactone – that is used in areas including food packaging, 3D printing and biomedical implants.
The straightforward process is easily scalable, meaning it should be possible to convert large quantities of plastics rapidly, the team says. The process can also be adapted to upcycle other types of plastic, further expanding its possible applications, they add.
Further research is needed to fully understand the possible environmental impacts of the breakdown products of polythionoesters.
The findings are reported in the journal Chem Circularity, a new sustainability focussed publication within the Cell Press portfolio. The research was funded by UK Research and Innovation (UKRI), the Royal Society, the French National Research Agency and the French National Centre for Scientific Research (CNRS).
Dr Jennifer Garden, of the University of Edinburgh’s School of Chemistry, who co-led the study, said: “The thionation of polyesters is a challenging task, as these materials are less reactive towards thionation than many other polymers, and accessing polythionoesters via traditional routes can be difficult. What makes this discovery so exciting is that we’ve successfully developed a strategy that opens the door to a whole new range of sulfur-containing materials. We’re eager to see where this research takes us and are already looking forward to exploring the many possibilities that this breakthrough has to offer, paving the way for future studies in this promising field. Collaborating with this team has been an absolute joy – their enthusiasm, motivation, and expertise have made every step of this journey a pleasure, and I feel fortunate to work alongside such a talented group of scientists.”
