Researchers have come up with a recyclable alternative to a robust category of plastics commonly used in products such as car tires, hip joint replacements, and bowling balls.
Researchers from Cornell University have introduced a recyclable substitute for a strong type of plastic often utilized in items like car tires, hip replacements, and bowling balls.
This type of plastic, known as thermosets, features a “crosslinked polymer” structure that enhances its durability. However, this very characteristic also makes these petrochemical-based materials — which account for 15%-20% of all produced polymers — impossible to recycle.
Brett Fors, a professor of chemistry and chemical biology at Cornell, noted, “Currently, none of the world’s thermoset materials are recycled. Instead, they are either incinerated or landfilled.”
The Fors laboratory has tackled this environmental issue by creating an alternative derived from bio-sourced materials. This new option retains the durability and flexibility typical of crosslinked thermosets but can be recycled and decomposed with ease.
“Our entire process, from production to reuse, is significantly more eco-friendly compared to existing materials,” explained Reagan Dreiling, a chemistry doctoral student and lead author of the study published in Nature.
The Fors team is focusing on dihydrofuran (DHF), a monomer made from biological sources which could one day rival petroleum-based materials.
Dreiling used DHF, a circular monomer featuring a double bond, to initiate two consecutive polymerizations. The second polymerization creates a crosslinked polymer that can be recycled through heating and will naturally decompose over time.
DHF thermosets demonstrate comparable qualities to commercial thermosets, such as high-density polyurethane (used in electronic devices, packaging, and footwear) and ethylene propylene rubber (common in garden hoses and automotive weatherstripping).
According to Fors, unlike conventional petrochemical thermosets, the DHF-based materials promote a circular economy. They can be chemically recycled back into their original building block monomer and reused. Moreover, if some of the material accidentally enters the environment, it will harmlessly break down over time.
The researchers aim to explore applications for the DHF-based materials, including making them suitable for 3D printing, and are testing additional monomers to enhance their properties.
“For a century, we have been focused on creating polymers that are everlasting, but we now recognize that’s not ideal,” Fors commented. “We are shifting towards developing polymers that are not permanent and can break down environmentally.”
