Researchers tackle polyurethane waste

Polyurethane is used in a wide range of applications such as varnishes, paints, car parts, seat cushions and insulation. As polyurethane is a plastic material, its chemical compounds can be manipulated to create flexible, pliable products; rigid, durable products; or liquid finishing products.

In the US, a reported 1.3 million tons of polyurethane waste is generated each year, which usually ends up in landfill or is incinerated, a process requiring significant energy input and generating toxic by-products.

A research team from the University of Illinois has developed a method to break down polyurethane waste and turn it into useful products. The team will present their findings at the American Chemical Society National Meeting and Exposition.

“We want to solve the waste problem by repurposing polyurethane,” said Ephraim Morado, a graduate student in the laboratory of Chemistry Professor Steven Zimmerman, who led the research.

Polyurethanes are made of two components that are hard to break down: isocyanates, composed of nitrogen, carbon and oxygen, and alcohol groups called polyols. Morado explained that polyol is usually petroleum based and is not degradable.

To address this difficulty, the team incorporated a more easily degraded chemical unit, an acetal, to the polyol. Because polyurethanes are water resistant, the researchers designed the acetal unit to degrade in solvents other than water.

“When we add a combination of trichloroacetic acid and dichloromethane, the material swells and rapidly degrades at room temperature,” Morado said.

The degradation products that are formed can then be repurposed into new materials. The researchers converted elastomers — a type of polyurethane used in rubber bands, packaging and car parts — into an adhesive glue.

“One of the challenges with our approach is that the starting material is costly,” Zimmerman said. “We are trying to find a better, cheaper way to accomplish this. Our second hurdle will be to get a patent and find someone who is interested in commercialising it.

“The polyurethane materials have different properties based on the chemical structure of the isocyanate,” Zimmerman said. “We can change the structure of the acetal accordingly.”

The researchers are testing the same technique on other polyurethane materials. They hope to use milder solvents, such as vinegar, to carry out the degradation.

Image caption: University of Illinois Chemistry Professor Steven Zimmerman, right, graduate student Ephraim Morado, and their colleagues are inventing new ways to degrade polyurethane and re-use the waste. Image credit: L Brian Stauffer.