New Bio-Based Thermosets Offer Durability and Recyclability

When we think of everyday items like car tires, replacement hip joints, and bowling balls, many of them have one thing in common: they’re made from a class of plastics called thermosets. These materials are known for their extreme durability. Their ability to maintain shape and strength over long periods of time has made them essential for a wide range of applications, from industrial products to medical devices. However, this durability also comes with a significant environmental drawback: thermosets cannot be recycled.

Unlike some plastics that can be melted down and reshaped, thermosets undergo a process known as crosslinking. This process chemically bonds the polymer chains together into a three-dimensional network that gives the material its impressive strength and stability. However, this very structure makes thermosets resistant to being broken down or recycled. As a result, 15%–20% of all plastics produced worldwide are thermosets, yet zero percent of these materials are currently recycled. Instead, they end up in landfills or are incinerated, creating significant environmental waste.

This unsustainable reality is where the research of Brett Fors, a professor of chemistry and chemical biology, and his team comes into play. They have developed a new class of bio-sourced thermosets that offer the same high durability and malleability as their petrochemical counterparts, but with a crucial difference: they can be easily recycled and even degraded naturally. This breakthrough addresses both the need for high-performance materials and the growing demand for environmentally friendly solutions.

The Chemistry Behind the Breakthrough

The solution lies in the development of thermosets made from a bio-sourced monomer known as dihydrofuran (DHF). Monomers are the basic building blocks of polymers, and DHF, a circular molecule with a double bond, offers unique properties that make it an ideal candidate for this new class of materials. Unlike conventional thermosets made from petroleum-based feedstocks, DHF can be derived from biological materials, making it a sustainable alternative.

The Fors team’s innovation is in the way DHF is used to create the polymer. They have developed a two-step polymerization process that starts with a flexible, recyclable polymer and ends with a tough, crosslinked material that retains the best qualities of traditional thermosets. Here’s how it works:

1. First Polymerization: The process begins by opening the circular DHF monomer and linking many of these open rings together to form a long, flexible chain. This first polymer is soft and flexible, and it can be chemically recycled. The key to recycling this polymer lies in its ability to break down when exposed to heat or acid, which reverts it back to its monomer form. This means that the material can be broken down and reused in the future, creating a circular economy for the polymer.
2. Second Polymerization: Not all DHF molecules are consumed in the first polymerization. The remaining DHF monomers are crucial for creating the final, tough thermoset material. The second polymerization process uses light to initiate and control the reaction, linking the remaining DHF molecules into a crosslinked network. This final material is strong, rigid, and exhibits the durability associated with traditional thermosets. The degree of crosslinking can be controlled by the amount of light used, which allows for fine-tuning of the material’s properties.

This innovative approach offers several advantages over conventional thermosets. For one, the final material is chemically recyclable—it can be reprocessed and broken down into its monomer components, ready to be reused. Furthermore, unlike petroleum-based thermosets, the DHF-based material is biodegradable. This means that if some of the material leaks into the environment, it will degrade into benign components over time, reducing the environmental impact.

Advantages Over Traditional Thermosets

Traditional thermosets, made from petroleum-based feedstocks, are virtually impossible to recycle because of their crosslinked chemical structure. Once they have been set into their final form, they cannot be remolded or repurposed. As a result, these materials often end up in landfills, where they persist for decades or longer. In fact, the disposal of thermosets represents a significant environmental challenge in the plastic waste crisis.

By contrast, the DHF-based thermosets developed by Fors and his team offer a solution to this problem. In addition to their recyclability, these bio-sourced materials can be chemically broken down and degraded in the environment, which is a significant improvement over current thermosets. This means that while these materials will remain durable and useful for their intended applications, they won’t contribute to long-term pollution or waste. Their biodegradability ensures that even if a product made from this material ends up in the environment, it will break down into harmless byproducts.

The DHF-based thermosets also show comparable properties to commercial thermosets such as high-density polyurethane (used in products like electronics, packaging, and footwear) and ethylene propylene rubber (used in automotive weatherstripping and garden hoses). This makes them a promising alternative for a wide range of applications, including those that require both flexibility and toughness.

A Simple and Efficient Process

One of the most remarkable aspects of this research is the simplicity and efficiency of the polymerization process. By using just a single monomer—dihydrofuran—and controlling two different polymerization steps, the Fors team has created a material that can be customized to meet specific performance requirements. The process is not only environmentally friendly but also cost-effective.

According to Reagan Dreiling, a doctoral student in Fors’s lab and the lead author of the study published in Nature, the process is highly versatile. “It’s so easy,” Dreiling says. “Just by changing the amount of time you run each reaction for, the amount of catalyst you put in each reaction, and the intensity of light you use, you can get a wide scope of properties through a simple process.” The ability to adjust the amount of crosslinking through light exposure means that the material can be tailored to have different levels of rigidity or flexibility, depending on the application.

The DHF-based thermosets also have another key advantage over traditional plastics: they can be processed at lower temperatures. This makes them easier to work with in manufacturing processes like 3D printing, where high heat can cause problems with material handling. Fors and his team are exploring how to expand the properties of DHF-based materials by adding additional monomers, which could lead to new applications and further improvements.

Moving Toward Real-World Applications

The next step for the Fors lab is to scale up the production of these bio-sourced thermosets and begin testing them in real-world applications. They are particularly interested in using these materials for 3D printing, where recyclability and biodegradability are increasingly important. The ability to 3D print objects using a material that is not only strong and durable but also environmentally friendly could have a major impact on industries ranging from electronics to automotive manufacturing.

The researchers are also continuing to explore other potential applications, including in medical devices, where the durability and flexibility of thermosets are essential. By developing a recyclable, bio-sourced alternative, Fors and his team could help reduce the environmental impact of medical plastic waste.

A Step Toward a Sustainable Future

For years, the goal of creating durable plastics that are also environmentally friendly has been a challenging contradiction. We’ve spent 100 years developing polymers that last forever, but as Fors points out, “We’ve realized that’s not actually a good thing.” Now, through the work of Fors and his team, scientists are moving toward the creation of polymers that don’t last forever—but can be recycled, reused, and degraded naturally when their life cycle ends.

This breakthrough is a significant step toward achieving a circular economy for plastics, where materials are not just discarded after their initial use but are continuously recycled and reused. By shifting from petroleum-based feedstocks to bio-sourced materials like DHF, we are not only addressing the issue of plastic waste but also paving the way for a more sustainable future.

As the research progresses, we can expect to see these new thermosets playing a key role in reducing the environmental impact of plastic products across multiple industries. With further development, they may offer a game-changing solution to one of the most pressing challenges of our time: the need for sustainable, recyclable, and biodegradable plastics.

Reference: Reagan J. Dreiling et al, Degradable thermosets via orthogonal polymerizations of a single monomer, Nature (2025). DOI: 10.1038/s41586-024-08386-w