Chemists at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have unveiled an innovative method to upcycle discarded plastics, offering a potential solution to the growing global plastic waste crisis. By editing the polymers of common plastic waste, the researchers have created new macromolecules with improved properties, such as greater strength, rigidity, and heat resistance. This breakthrough could dramatically reduce the environmental impact of plastic waste, which amounts to roughly 450 million tons annually, with only 9% of it being recycled. The rest is either incinerated or ends up in landfills and oceans, contributing to environmental pollution.
The new technique, detailed in a study published in the Journal of the American Chemical Society, harnesses molecular editing to rearrange polymeric building blocks, enabling the creation of more versatile and higher-performance plastics from waste materials. The method allows for precise modification of polymer chains, turning low-value, discarded plastics into valuable resources with a wide range of applications.
At the heart of this research is a process that uses a combination of chemical reactions to break and reassemble plastic polymers into new forms. The team worked with two widely used, difficult-to-recycle plastics: polybutadiene (a key component of rubber tires) and acrylonitrile butadiene styrene (ABS), a tough plastic found in products like toys, electronics, and vehicle parts.
“This process isn’t the typical ‘melt and hope for the best’ approach to recycling,” said Jeffrey Foster, the ORNL scientist who led the study. “Instead, we are editing polymer chains with precision, much like CRISPR edits DNA, to create new and improved plastic materials.”
The team employed a ruthenium catalyst, widely used in industrial plastic production, to facilitate polymerization at low temperatures (40°C) for less than two hours. This allowed the waste plastics to dissolve and undergo a chemical reaction that altered their molecular structure, effectively “upcycling” them into higher-value forms.
The new upcycling process works by breaking and reforming the double bonds between carbon atoms in the polymer chains, a technique known as “metathesis.” This allows the polymer subunits to swap places and form new polymer chains, a process with several advantages over traditional recycling methods.
“Traditional recycling typically results in plastics that degrade over time, becoming weaker with each melt and reuse,” Foster explained. “In contrast, our method preserves the integrity of the material, allowing it to maintain, or even enhance, its original properties.”
The ORNL process uses two types of metathesis: ring-opening metathesis polymerization (ROMP), which elongates carbon rings into chains, and cross metathesis, which exchanges polymer subunits between different polymer chains. These processes allow the researchers to customize the properties of the resulting plastics, making them more flexible, stretchable, or durable, depending on the desired application.
One of the key advantages of the new method is its high atom economy, meaning it efficiently recovers nearly all of the material involved in the process. This stands in stark contrast to traditional recycling, which often loses a significant portion of material during processing.
In addition to being energy-efficient and producing fewer emissions than conventional recycling, the new process has the potential to significantly reduce the amount of plastic waste that ends up in landfills or the ocean. By upcycling plastics into higher-value materials, the ORNL team hopes to contribute to a more sustainable circular economy, where waste materials are repurposed rather than discarded.
“By transforming plastic waste into useful products, we can reduce our reliance on virgin plastic production and alleviate the environmental burden of plastic waste,” Foster said.
While the initial focus has been on polybutadiene and ABS, the researchers are optimistic that the upcycling process could be adapted to other types of plastics as well. They aim to explore how different subunits within the polymer chains can be rearranged to create even higher-performance materials, such as thermoset plastics like epoxy resins, vulcanized rubber, and polyurethane.
Thermoset materials are particularly challenging to recycle because their molecular structure becomes cross-linked during curing, making them impossible to remelt or reshape. However, the ORNL team believes that their method could be extended to these materials as well, potentially offering a new way to recycle and repurpose some of the most difficult-to-process plastics.
In addition, the team is investigating ways to optimize solvents for industrial-scale processing, ensuring that the upcycling process is both effective and environmentally sustainable.
Looking ahead, the ORNL researchers hope to scale up their upcycling process and apply it to a wider range of industrially important polymers. By doing so, they aim to create a more sustainable future for plastic production, where waste materials are no longer discarded but instead transformed into valuable resources.
“The ultimate goal is to make plastic upcycling a viable and economically attractive option for industries worldwide,” Foster said. “By tapping into the potential of plastic waste, we can reduce environmental pollution, conserve resources, and support the growth of a circular economy.”
The work at ORNL represents a significant leap forward in the effort to tackle the global plastic waste crisis and demonstrates the transformative potential of chemical upcycling in reshaping the future of plastics.
By Impact Lab