Here’s what you’ll learn when you read this story:

• Researchers have found a way to synthesize polyesters from leftover cooking oil, including a powerful adhesive.
• The fatty acids in cooking oil are ideal for making polymers because the hydrocarbon chains in these fats provide flexibility, durability, and moisture resistance.
• When compared to commercial adhesives, the cooking oil glue either matched or outperformed them.

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Plastics like polythene (think plastic bags) and polyethylene have been taking over landfills and encroaching on the environment to the point that creatures in the deep sea are even ingesting them. But soon, they could be replaced by comparable materials made from cooking oil that is no longer usable. Now, oil that would have otherwise been thrown away has been turned into another kind of eco-friendly polymer—an absurdly strong glue.

Led by polymer research and development scientist Nargarjuna Mahadas from the University of South Carolina, a team of researchers were able to synthesize several materials that behaved remarkably like polyethylene—they have all the strength and flexibility without the need for fossil fuels. While changing the properties of these polymers by making them more rigid with a linear polymer chain or more flexible with a branched polymer chain, Mahadas discovered that some of them were sticky. And there was one which turned out to be an especially strong adhesive.

“These materials […] rival low-density polyethylene (LDPE) in flexibility and strength and notably outperform commercial adhesives in shear strength by creating robust yet temporary bonds with multiple substrates, offering safety, ease of handling, and removability,” Mahadas said in a study recently published in the Journal of the American Chemical Society.

So, why is leftover cooking oil so useful for making polymers? Well, that stuff is packed with triglycerides, which are full of saturated and unsaturated fatty acids. These notoriously artery-clogging fats take a heroic turn when recycled into substances like biodiesel, lubricants, coatings, and plastics.

Triglycerides have especially complex compositions that were previously intimidating to approach in the synthesis of plastics, but they possess the same hydrocarbon chains that make polyethylene so durable, so scientists figured they were worth experimenting with. And, unlike fossil fuels (which exist in finite reserves), waste cooking oil is nowhere close to being in short supply—about 3.7 billion gallons are generated each year.

To synthesize polymers, Mahadas and his team broke down the unsaturated fatty acids and glycerol in cooking oil into monomers. Fats were reduced to diols (organic compounds containing double hydroxyl groups attached to different carbons in molecules), which are important for creating polymers, as hydrogen bonding gives them durability, flexibility, and moisture resistance. Monomers were then reassembled into polyesters. The ester bonds (covalent bonds formed by a carboxylic acid and an alcohol in the backbone of these materials) make them biodegradable and recyclable.

The glue developed by the researchers was tested on stainless steel, copper, softwood, and cardboard, and its effectiveness was also compared to that of commercial EVA and epoxy resin. When the researchers glued stainless steel plates together, the plates stayed together even when used to tow a sedan on a slope with a slight incline (and the average mid-size sedan weighs between 3,100 to 3,500 pounds). It could also be molded into a glue stick and used in a hot glue gun, just like the EVA glue sticks available in craft stores. This alternative adhesive was easily used to seal a cardboard box, and when it was used to bond objects to heavy weights, it could lift up to 270 pounds without the bond breaking.

“Compared to conventional polyethylene, these materials offer distinct advantages in sustainability, recyclability, and adhesion,” said Mahadas. “Overall, this work highlights the potential of nonedible biomass waste as a renewable feedstock for high-performance materials, advancing the development of environmentally friendly alternatives to petroleum-based plastics.”

Elizabeth Rayne is a creature who writes. Her work has appeared in Popular Mechanics, Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.