Waste Not
Cornell Researchers Upcycling Polyester Textile Waste into Functional Coatings

With a goal of giving textile waste new life, Cornell University researchers have found a way to chemically break down old clothing and reuse polyester compounds to create fire-resistant, anti-bacterial or wrinkle-free coatings that can then be applied to new clothes and fabrics.

The proof-of-principle study provides hope for the unsustainable textile, apparel and footwear industries — which together generate 20 percent of global solid waste; the Ellen MacArthur Foundation estimates 73 percent of all textiles end up incinerated or in landfill. Many so-called recyclers end up illegally dumping textiles as trash in countries in Asia and Africa; and many other brands and companies just incinerate the materials — which releases greenhouse gases, dioxins and toxic substances into the environment.

"We think that our clothes are recycled or reprocessed; but most of the time they are actually sent to other places as solid waste," said Juan Hinestroza, professor of fiber science and apparel design and director of Cornell’s Textiles Nanotechnology Laboratory. "Our main goal is to offer a pathway to reuse this material."

Blended textiles — typically comprised of natural fabrics such as cotton and synthetic fabrics such as polyester — have until recently stymied textile recyclers, which lacked the ability to easily separate the fibers for reuse. Recent innovations from startups such as Circle Economy, Protein Evolution and Worn Again have removed this barrier — enabling easy separation and recycling of pesky blended textiles for reuse.

But the Cornell study, which was partially funded by the National Science Foundation, may be the first to upcycle old textiles into a number of high-performance coatings for new textiles. Upcycling of Dyed Polyester Fabrics into Copper-1, 4-Benzeedicarboxylate Metal-Organic Frameworks — published March 30 in the journal Industrial & Engineering Chemistry Research — describes the process of cutting textiles into pieces and chemically decomposing them into a soup of raw materials, dyes, additives, dirt and esters. A metal solution is added and building blocks from the polyester share an affinity with the metal, and selectively link together metal compounds forming tiny cages (called metal-organic frameworks or MOFs) that settle to the bottom of the soup.

The cages that form are then used to make coatings, which may require minor structural tweaks to tailor each to specific uses — including coatings that keep permanent press apparel from wrinkling, antibacterial coatings for surgical gowns or scrubs, or fire-retardant coatings for baby or industrial clothes or furniture.

"One goal of my lab is to create a universal coating that will serve all these purposes; though we are still far away from that," said Hinestroza, who co-authored the paper with Yelin Ko, a doctoral student at Cornell’s Department of Human-Centered Design; and Tyler Azbell and Phillip Milner, from the University’s Department of Chemistry and Chemical Biology.

Hinestroza and Ko began working on a circular uses for discarded polyester in 2022. By converting polyester into MOFs, they have been able to repurpose the porous MOFs into an array of uses. Previous research attempts required the use of harsh solvents, but Hinestroza has discovered a process that takes just 30 minutes and requires no extreme chemicals or temperatures. MOFs have a cage-like structure that can capture molecules. When MOFs are electrospun into nanofiber, they can be used in medical textiles and protective apparel, gas-separation or even drug-delivery applications. Already applicable to both dyed and undyed fabric, Hinestroza’s Lab is now demonstrating that the new MOF-treated material can create MOFs again and again, creating a circular polyester loop that will divert the materials from landfill — and potentially offering non-toxic alternatives to these common, conventionally harmful chemical coatings.

Prior to this research, some believed the dyes and impurities in the mix would interfere with the process, but this proof of principle of the method — known as controlled crystallization — shows that the polyester-derived linkers can seek out and attach to metal compounds in solution, in spite of other materials that may be present.

The research describes a closed-loop process, where discarded materials may be reused and contribute to a circular economy — a focus for many sustainability researchers at Cornell, Hinestroza said.