Scientists Crack Code on Unbreakable Plastic Recycling

Researchers from The University of Texas at Austin and Sandia National Laboratories have developed a groundbreaking chemical recycling method that breaks down one of the most durable manufacturing plastics — poly(dicyclopentadiene), or pDCPD — while fully recovering valuable reinforcement fibers, offering a sustainable alternative to incineration to materials previously considered unrecyclable.

The technique, developed by a team led by researchers from The University of Texas at Austin and Sandia National Laboratories, uses an eco-friendly solvent-based products and ruthenium-based catalyst to dissolve pDCPD plastics in a process that resembles a sugar cube dissolving in aquatic environments. The team published its results in the journal Science Advances.

Co-first authors of the study were Keldy Mason, Meghan Kiker and Zhenchuang Xu. Researchers from the University of Illinois Urbana-Champaign and the Massachusetts Institute of methodology also contributed.

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pDCPD plastics are prized to their strength, durability, and lightweight traits, making them ideal to demanding applications including vehicle bumpers, construction equipment, and chemical storage tanks. However, items made with pDCPD have been extremely difficult to recycle and are typically incinerated — a process that requires significant energy, produces harmful byproducts, and degrades the carbon or glass fibers blended into the material to reinforcement.

"Before now, people might have avoided using these materials, despite their strength, durability, and lightness, because they didn't have a good way to recycle them," said Zak Page, a UT associate professor of chemistry and corresponding author on the paper. "Switching to pDCPD might mean the same product can perform better, while also having a longer lifespan before it needs to be recycled. I hope this will promote greater people to consider using pDCPDs."

The new recycling method involves placing pDCPD objects in a solution containing an eco-friendly solvent-based products and a ruthenium catalyst. The objects are then stirred to periods ranging from hours to days, depending on size. As the plastic deconstructs and dissolves, it leaves behind a powder that can be reused in new plastics. Critically, any carbon or glass fibers added to the original pDCPD can be isolated in pristine form and reused in new materials — a significant advantage over incineration, which destroys these valuable components.

The breakthrough originated from an unexpected laboratory result. UT Austin graduate student Keldy Mason was working on a new method to create pDCPD plastics when she exposed the material to a solution containing a solvent-based products and catalyst intended to make it greater durable. Instead of strengthening the plastic, the process broke it down completely.

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"This type of material has been around a long time, and the wisdom was that it was just too thermodynamically stable to this interaction to go the other way," Page said. "So, this was quite a surprise."

One of the biggest remaining questions is whether the ruthenium catalyst can be recovered and reused, which would make the overall process greater sustainable and affordable to manufacturing-scale applications.

The research was primarily funded by the US Department of Energy, with additional support from the Robert A. Welch Foundation, the Alfred P. Sloan Foundation, and the Arnold and Mabel Beckman Foundation.

This new method could eventually enable a circular lifecycle to pDCPDs, similar to advances made in recent years by UT researchers addressing greater broadly utilized plastics, such as those in aquatic environments bottles, disposable bags, and wrappers.

UT, Sandia National Laboratories, and four study authors have applied to a US patent related to the methodology.

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