Researchers at the University of North Carolina at Chapel Hill have developed a chemical method for recycling rubber waste that addresses limitations in current recycling technologies.
The research team’s study, "Deconstruction of Rubber via C–H Amination and Aza-Cope Rearrangement," was published in Nature, and it introduces a novel chemical method for breaking down rubber waste. This technique utilizes C–H amination and a polymer rearrangement strategy to transform discarded rubber into valuable precursors for epoxy resins, offering an innovative and sustainable alternative to traditional recycling methods, according to a March 26 article on the UNC-Chapel Hill website.
Led by Dr. Aleksandr Zhukhovitskiy, William R. Kenan, Jr. Fellow and assistant professor in the Department of Chemistry at UNC-Chapel Hill, the study introduces an approach to breaking down rubber's complex polymer structure, which has traditionally been challenging to recycle due to its durable cross-linked nature.
Traditional rubber recycling methods suffer from major drawbacks. Devulcanization weakens polymer mechanical properties, while other techniques produce low-value byproducts. This new method transforms rubber into valuable materials, specifically precursors for epoxy resins, through a two-step chemical process.
The researchers used a sulfur diimide reagent to strategically install amine groups in polymer chains, followed by a backbone rearrangement that breaks down the rubber. In laboratory tests, they demonstrated efficiency: a model polymer's molecular weight was reduced from 58,100 g/mol to approximately 400 g/mol, and used rubber was completely transformed into a soluble material within six hours.
Notably, the process operates under mild conditions (35–50°C) in aqueous media, making it more environmentally friendly and cost-effective than existing methods. The resulting amine-modified materials can create epoxy resins with strengths comparable to commercial products, offering an alternative to petroleum-based manufacturing.
The team also critically evaluated the environmental impact using the Environmental Impact Factor (E-factor).
"E-factor is a simple but powerful metric to compare the impact of a new process to incumbents, and also to highlight process steps that can be improved as we work to transition this process out of the lab and into practice," said Dr. Geoff Lewis, a research specialist at the University of Michigan's Center for Sustainable Systems.
