New method causes plastics to break down under UV light

Researchers in the UK have developed a novel method to break down plastics using just ultraviolet (UV) light.

The researchers at the University of Bath discovered that adding sugar units to polymers increases their degradability when exposed to UV radiation.

UV radiation has a wavelength of 10 nanometres (nm) to 400 nm, shorter than that of visible light, but longer than X-rays.

Many plastics that bear the biodegradable label can only be composted in industrial settings.

The researchers noted that public concern about plastic waste has led to the widespread usage of PLA (Poly lactic acid), which is a renewable, sustainable alternative to polymers made from crude oil.

PLA is used in everything from throwaway cups and teabags to three dimensional (3D) printing and packaging.

Although PLA is sometimes advertised as biodegradable, it only dissolves under industrial composting conditions of high temperatures and humidity, which are not possible in residential compost heaps.

It is also not easily degradable in natural environments, such as soil or the ocean.

"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 Antoine Buchard from the University of Bath.

The research, recently published in the journal Chemical Communications, demonstrated a method that could increase the rate at which these polymers degrade in the environment.

The researchers found that by adding various quantities of sugar molecules to the polymer, they could modify how quickly the plastic degrades.

They discovered that incorporating as little as 3 per cent of sugar polymer units into PLA caused it to degrade by 40 per cent in only six hours when exposed to UV light.

"Most PLA plastics are made up of long polymer chains which can be difficult for water and enzymes to break down.

"Our research adds sugars into the polymer chains, linking everything together by bonds that can be broken using UV light," said Buchard, who led the research.

The method weakens the plastic, breaking it down into smaller polymer chains that are then more sensitive to hydrolysis.

This could make the plastic much more biodegradable in the natural environment, for example in the ocean or in a garden compost heap.

The technology is compatible with existing plastic manufacturing processes, meaning it could potentially be tested and adopted quickly by the plastics industry, the researchers said.

They 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.