Scientists are using everyday plastics to start innovative chain reactions, developing a method to recycle plastic waste and improving the safety and efficiency of the process.

Single-use plastic is a major environmental problem, but instead of being thrown away as garbage, used plastic bags from grocery stores can now be used to carry out a reaction that can detoxify dangerous chemicals.

A team led by researchers from Hokkaido University’s Chemical Reaction Design and Discovery Institute (WPI-ICReDD) has developed a method that uses common plastic materials instead of potentially explosive compounds to initiate radical chain reactions. This approach significantly increases the safety of the process and also enables the reuse of common plastics such as polyethylene and polyvinyl acetate. These results were published in: Journal of the American Chemical Society.

The researchers used a ball mill, a machine that rapidly shakes a steel ball inside a steel can, to mix solid chemicals. When the ball hits the plastic, the mechanical force breaks the chemical bond with the formation of radicals with highly reactive unbonded electrons. These radicals promoted a self-sustaining chain reaction that promoted dehalogenation. well replacement of the halogen atom with a hydrogen atom (organic halides).

Improving chemical processes

“Using commercial plastics as chemical reagents is a completely new approach to organic synthesis,” said Associate Professor Koji Kubota. “I believe this approach will lead not only to the development of safe and highly effective radical-based reactions, but also to a new method of disposing of plastic waste, a serious social problem.”

Associate Professor Koji Kubota (left) and Professor Hajime Ito (right) from the research group of Hokkaido University’s Chemical Reaction Design and Discovery Institute (WPI-ICReDD). Credit: WPI-ICReDD

The reuse of plastic waste was demonstrated by adding plastic pieces of a regular shopping bag to the jar of a ball mill and the reaction was successfully carried out. The team also showed that their method can be applied to the treatment of highly toxic polyhalogenated compounds commonly used in industry. Polyethylene was used to initiate a radical reaction that removed a few halogen atoms from a compound commonly used as a flame retardant, thus reducing its toxicity.

Researchers expect this method to attract industry attention due to its cost and safety advantages.

“Our new approach, which uses stable, inexpensive and widely used plastic materials as initiators of radical chain reactions, has significant potential to facilitate the development of industrially attractive, safe and highly efficient chemical processes,” commented Professor Hajime Ito.

The research was funded by the Japan Society for the Promotion of Science, the Japan Science and Technology Agency, and the Japan Ministry of Education, Culture, Sports, Science and Technology.