Researchers at the Georgia Institute of Technology have developed a new method to break down plastic using mechanical forces rather than heat or harsh chemicals, paving the way for faster and more sustainable recycling.
Polyethylene terephthalate (PET) is one of the world’s most widely used plastics, found in bottles, food packaging, and clothing fibres. However, its durability makes it difficult to recycle efficiently.
The new study, published in the journal Chem, demonstrates how a “mechanochemical” method – chemical reactions driven by mechanical forces such as collisions – can convert PET back into its basic building blocks.
Led by postdoctoral researcher Dr Kinga Gołąbek and Professor Carsten Sievers of Georgia Tech’s School of Chemical and Biomolecular Engineering, the research team struck solid pieces of PET with metal balls at a force similar to that generated in a ball mill. This caused the PET to react with solid chemicals such as sodium hydroxide (NaOH), breaking the plastic’s chemical bonds at room temperature without the need for hazardous solvents.
“We’re showing that mechanical impacts can help decompose plastics into their original molecules in a controllable and efficient way,” Sievers said. “This could transform the recycling of plastics into a more sustainable process.”
To understand how the process works, the team conducted controlled single-impact experiments alongside advanced computer simulations to map how energy from collisions distributes through the plastic and triggers chemical and structural transformations.
“These experiments showed changes in structure and chemistry of PET in tiny zones that experience different pressures and heat,” the researchers noted.
By mapping these transformations, they gained new insight into how mechanical energy triggers rapid and efficient chemical reactions.
“This understanding could help engineers design industrial-scale recycling systems that are faster, cleaner, and more energy-efficient,” Gołąbek said.
Each collision created a small crater in the material, with the centre absorbing the most energy. In this zone, the plastic stretched, cracked, and softened slightly, creating ideal conditions for chemical reactions with sodium hydroxide. High-resolution imaging revealed that normally ordered polymer chains became disordered, while some broke into smaller fragments, increasing the surface area available to react.
Even without sodium hydroxide, mechanical impact alone caused minor chain breaking, showing that mechanical force itself can trigger chemical change.
The study also found that the amount of energy delivered by each impact was crucial. Low-energy collisions caused little change, while stronger impacts created cracks and deformations that exposed new surfaces, enabling faster breakdown.
“Understanding this energy threshold allows engineers to optimise mechanochemical recycling, maximising efficiency while minimising unnecessary energy use,” Sievers said.
According to the researchers, the findings could lead to a future where plastics are fully recycled into their original components rather than downcycled or discarded.
“This approach could help close the loop on plastic waste,” Sievers said. “We could imagine recycling systems where everyday plastics are processed mechanochemically, giving waste new life repeatedly and reducing environmental impact.”
The team now plans to test the method on real-world waste streams and explore its potential for other hard-to-recycle plastics.
“With millions of tons of PET produced every year, improving recycling efficiency could significantly reduce plastic pollution and help protect ecosystems worldwide,” Gołąbek said.