PLA, or polylactic acid, is a bio-based plastic that is increasingly finding application as a renewable, sustainable alternative to plastics derived from crude oil products. Today, PLA, which is produced from lactic acid derived from the fermentation of sugars, is used in everything from disposable cups and teabags to 3D printing and packaging.
However, PLA has limited degradability in natural environments, such as soil or seawater, and it only degrades under industrial composting conditions of high temperatures and humidity – not achievable in domestic compost heaps. Now a team of scientists led by Dr Antoine Buchard, Royal Society University Research Fellow and Reader in Polymer Chemistry at the Centre for Sustainable and Circular Technologies (CSCT) at the University of Bath, have developed a way that could make these plastics more degradable in the natural environment.
“Lots of plastics are labelled as biodegradable, but unfortunately this is only true if you dispose of it in an industrial waste composter - if put into domestic compost heaps, it can last for years,” said Buchard.“Most PLA plastics are made up of long polymer chains which can be difficult for water and enzymes to break down.
The team found that they can tweak the degradability of the plastic by incorporating different amounts of sugar molecules into the polymer. By incorporating as little as three per cent sugar polymer units into PLA they were able to achieve 40% degradation within six hours of exposure to UV light.
“This weakens the plastic, breaking it down into smaller polymer chains that are then more sensitive to hydrolysis,” explained Buchard. “Previously scientists have looked at enhancing the degradability of PLA to water – hydrolysis - but this is the first time anyone has looked at using light.”
The technology is compatible with existing plastic manufacturing processes, meaning it could potentially be tested and adopted quickly by the plastics industry. The mechanism of degradation requires to be investigated in detail, and this strategy remains to be translated to real-life plastics objects, but it has the potential to increase the environmental degradability of PLA without significantly affecting its material properties.
Publishing in Chemical Communications (open access article), the researchers hope their findings will be used in the future by the plastics industry to help make plastic waste more degradable at the end of the life of the product.