Scientists Turn Hard-to-Recycle PVC Plastic Into High-Performance Engine Lubricant

Virginia Tech chemist and chemical engineer Guoliang 'Greg' Liu and his research team have developed a method for transforming polyvinyl chloride (PVC) — a plastic used in items such as plumbing pipes, window frames and credit cards — into polyalphaolefin, an important ingredient in lubricants including engine oil. The work, published Aug. 5 in Nature, could address two problems at once: the difficulty of recycling PVC, which is especially hard to recycle because it contains chlorine and a wide range of manufacturing additives, and the environmental cost of producing industrial lubricants.

In the process, researchers place PVC in a solvent, then add aluminum trichloride and alpha olefins and heat the mixture to 158 degrees Fahrenheit for three hours, after which they extract a relatively thick oil that functions as a lubricant. The project grew out of earlier work by Liu's team, published in Science and Nature Sustainability, on converting other types of plastic waste into surfactants used in soaps and detergents.

The researchers initially tried to chemically transform PVC by replacing its chlorine atoms with other chemical groups, but the resulting materials were soft, gooey and did not perform well. Liu said the turning point came when he decided to keep breaking the polymer chains down into smaller segments instead, which produced a material with unexpected value as a lubricant. Doctoral student Eric Munyaneza Nuwayo led the effort, working with graduate students Connor S. Thompson and Abby Civiello — a trio Liu called 'the three musketeers.'

To test what the team had created, Liu sent samples to Ali Erdemir at Texas A&M University for performance testing and worked with William Goddard at Caltech on chemical computations; Virginia Tech's Xi Chen contributed an economic and production analysis for manufacturing the oil at larger scale.