Polyurethane (PU) foams are relatively ubiquitous in today’s world, used in all types of cushioning, from car seats to mattresses. Used for nearly a century, the material has been notoriously challenging to recycle due in large part to its complex chemical structure. And with millions of mattresses being thrown out annually, each with 15 to 20 kg of PU foam in them, there is a lot of waste to contend with. Fortunately, there have been a number of efforts in recent years to facilitate PU foam recycling. At Covestro, for instance, a team developed a chemical recycling process for PU foam from used mattresses back in 2021. Elsewhere, research teams are also devising innovative methods for reducing this stream of waste.
At the Indian Institute of Science (IISc) in Bengaluru, for example, a team of scientists has developed SaLSO, a patented technology capable of turning PU foam waste into 3D printing feedstock. The team, led by Professor Suryasarathi Bose and Professor Subodh Kumar, has found a way to selectively separate chemical bonds in PU foams, which effectively breaks down the hard-to-recycle material into various chemical components, which can then be used in the makeup of new 3D printing materials.
Chemical recycling is an emerging field that offers an alternative to more conventional mechanical recycling processes (which involve cleaning, melting and reprocessing plastic materials). In the chemical recycling process, polymers are broken down into their original monomer building blocks, which can then be polymerized into new materials. Chemical recycling processes have the greatest potential for reducing waste streams associated with difficult-to-recycling plastics, such as PU foams. Unlike mechanical recycling, chemical recycling also results in the production of virgin-quality materials, which as the British Plastics Federation says “enables the production of food grade plastics from post-consumer waste.”
The SaLSO process developed at IISc is compatible with different hardnesses of PU foam and is up to 98% effective. According to the researchers, the patented technology can also be used to break down and transform other plastics, like epoxy, unsaturated polyesters and polyolefins, into raw materials for 3D printing.
“This is a major leap in plastic waste management,” Professor Bose said in the Deccan Herald. “We’ve developed a sustainable solution to upcycle materials that were previously considered unrecyclable and patented a technology to convert long-unrecyclable PU foams and other challenging plastics into valuable 3D printing materials, breaking a major barrier in plastic waste management.” Professor Bose also recently played a role in the development of a sustainable hydrogel that can degrade microplastics using UV light, which could have an impact in removing microplastic pollution from water.
