Used cooking oil yields super strong glue and recyclable plastics

Plastics are made from crude oil and petroleum by-products, so a team of scientists decided to explore if they could turn waste cooking oil into a useful plastic material, and they succeeded.

The researchers converted waste cooking oil (WCO) into chemically recyclable polyesters—a type of synthetic plastic—that can serve as an alternative to the widely used fossil-fuel-based polyethylene (PE). This pursuit also resulted in a powerful adhesive that bonded stainless steel plates so strongly that it was able to pull a four-door sedan up a slight hill, as per the findings published in the Journal of the American Chemical Society.

Slippery to sticky

Polyethylene is the most widely produced plastic in the world because its hydrocarbon backbone makes it highly resistant to degradation. However, the same property that makes it useful also contributes to environmental pollution. Since PE-based products—such as plastic bags, food containers, and plumbing pipes—are non-degradable and not easily recycled, they often end up adding to the heaps of plastic in landfills and have even made an appearance in the Great Pacific Garbage Patch.

Over the years, scientists have made several attempts to develop materials that could replace PE, but its high performance and low-cost production have made the switch difficult. For any alternative to be truly viable, the starting material has to be cheap and eco-friendly and result in a final product that remains strong, versatile, and durable. Most PE alternatives fail to meet this checklist.

With sustainability in mind, one material gaining attention in this field is waste cooking oil. Each year, the world produces approximately 3.7 billion gallons of it, a largely untapped resource that could serve as a sustainable feedstock for plastic production if used appropriately.

In this study, the researchers first converted waste cooking oil unsaturated fatty acids into a long-chain C19-diester using a palladium catalyst, which was then reduced to form a long-chain diol. The resulting diol formed the main linear-chain structure required to mimic polyethylene (PE). Glycerol, another major component of waste cooking oil, was turned into branched 1,3-diols.

By polymerizing the branched and linear building blocks, the researchers designed a series of new polyesters (P1–P7) to mimic the properties of polyethylene. Their tests revealed that the polyesters matched or sometimes even surpassed low-density PE in both flexibility and strength.

Unlike PE, which is difficult to recycle, the new polymers/plastics could be readily broken down with chemical reagents, recycled, mixed with conventional plastics, and rebuilt into new plastics under mild conditions. The polymers made from branched diols showed strong adhesive performance across a wide range of surfaces, even outperforming commercial adhesives.

The researchers note that these findings establish the potential of waste cooking oil as a viable feedstock for plastic production. It also demonstrates a robust waste-to-materials strategy that aligns with circular-economy principles and highlights the potential of biomass to advance sustainable plastics innovation.

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