Giving Old Plastics New Life: Northwestern Researchers’ Novel Recycling Process

a view of the mountains through the open frame of a home being built. the foam insulation has just been applied to the walls.

(Credit: Unsplash.com)

by | Sep 6, 2023

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a view of the mountains through the open frame of a home being built. the foam insulation has just been applied to the walls.

(Credit: Unsplash.com)

Polyurethane plastics, found in a wide array of everyday products from mattresses to shoes, have long been a challenge in the world of recycling. These plastics, known as thermosets, possess crosslinked structures that resist traditional recycling methods. However, a group of researchers at Northwestern University has made a groundbreaking discovery. They’ve developed a new recycling method for polyurethane foams that employs nontoxic catalysts, ushering in a more sustainable future for these ubiquitous materials.

A Polyurethane Predicament: The Recycling Process Unveiled

Polyurethane plastics are omnipresent in our lives, but their end-of-life journey often ends in landfills and oceans, contributing to environmental pollution. Conventional recycling methods fall short when it comes to these materials due to their crosslinked structures.

In a recent breakthrough, Northwestern University researchers, led by William Dichtel (the Robert L. Letsinger Professor of Chemistry), have unlocked a new path for polyurethane recycling. They’ve identified nontoxic catalysts that enable the transformation of used polyurethane foam into a valuable resource.

The innovative recycling process involves a series of chemical reactions that simultaneously reprocess and “refoam” polyurethane. It starts with heating the material in the presence of a zirconium-based catalyst and a foaming agent. This process not only maintains the foam’s durability and structural integrity but also enhances its sustainability.

A ‘Circular Life Cycle’ for Plastics: Reshaping Polyurethane

Dichtel and his team’s achievement aligns with the concept of a “circular life cycle” for materials. This approach aims to reprocess or remanufacture materials with minimal loss of quality and value, a stark contrast to the linear, disposable model that currently dominates the plastics industry.

Traditional polymer recycling often involves melting plastics down for reuse. However, when it comes to more durable plastics like polyurethanes, this approach falls short due to their crosslinked structure.

The Northwestern team’s method introduces a zirconium-based catalyst, which rearranges the material’s bonds, allowing it to be reshaped. Simultaneously, a foaming agent generates new gas bubbles within the plastic, transforming old polyurethane foam into a new, reshaped foam product.

Collaborative Innovation

This breakthrough builds on Dichtel’s earlier research, which focused on recycling polyurethane foam into solid plastics. While significant, these solid plastic products were not commercially viable. The collaboration with scientists from BASF, a major polyurethane producer, enabled the team to take a giant leap forward by recycling one foam into another foam product.

Global Implications

The impact of this new recycling technique extends far beyond the Northwestern University campus. It has the potential to revolutionize the recycling of post-consumer polyurethane foam products and unused industrial scrap plastics on a global scale. The research team, in collaboration with BASF, aims to further advance the circularity and sustainability of polyurethane materials.

This research received support from the REMADE Institute, the National Science Foundation through the Center for Sustainable Polymers, and the NSF Graduate Research Fellowship Program. With this innovative approach to recycling, Northwestern University is paving the way for a greener and more sustainable roadmap for polyurethane plastics, giving old plastics new life and reducing their environmental footprint.

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