Polyurethane foams are notoriously difficult to recycle and currently end up in landfills or in lower value products, such as synthetic carpets. Photo: Northwestern University.Researchers have developed a new method for upcycling polyurethane foams, the spongy material found in mattresses, insulation, furniture cushions and shoes.
This method, developed by researchers at Northwestern University and the University of Minnesota, first involves mixing postconsumer polyurethane foam waste with a catalyst solution that allows the foam to become malleable. Next, the method utilizes a ‘twin-screw’ extrusion process to remove air from the foam to create a new material, in the shape of either a hard, durable plastic or a soft, flexible film, and re-mold the material.
This allows foam waste to be processed into higher quality rubbers and hard plastics for use in shoe cushioning, watch wristbands, hard durable wheels (for shopping carts and skateboards) and in automotive applications, such as bumpers. The researchers report their new method in a paper in ACS Central Science.
"Polyurethane foam waste has historically been landfilled and burned or downcycled for use in carpeting," said William Dichtel, professor of chemistry in Northwestern's Weinberg College of Arts and Sciences, who co-led the research. "Our latest work effectively removes air from polyurethane foams and remolds them into any shape. This could pave the way for industry to begin recycling polyurethane foam waste for many relevant applications." Dichtel co-led the research with Christopher Ellison, an associate professor of chemical engineering and materials science at the University of Minnesota.
Often made from toxic building blocks, polyurethane foam is a stubborn material that frequently ends up at the bottom of landfills. While other types of plastics can be melted down and recycled, polyurethane foam's chemical bonds are so strong that it does not melt – even at extreme temperatures. At best, people can shred it into synthetic fibers, which can then be downcycled into carpet and brushes.
Other upcycling efforts have compressed the foam to remove its air, but this resulted in cracked or unevenly blended materials. Dichtel and Ellison's approach uses two intermeshing, co-rotating screws to simultaneously mix and remold the foam, which improves mixing and air removal.
This story is adapted from material from Northwestern University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.