The New Recycling Process Can Reduce Millions Of Tons Of Plastic Waste

Multilayer plastic materials are everywhere in food packaging and medical supplies, especially because polymer coatings can provide film-specific properties for films, such as heat or oxygen resistance and steam control. But despite its usefulness, the plastics that once existed are not possible to be recycled using conventional methods.

About 100 million tons of multilayer thermoplastics – each consisting of as many as 12 different layers of polymer – are produced globally each year. Forty percent of the total is waste from the manufacturing process alone, and because there is no way to separate the polymer, almost all of the plastic is up to the pile or incinerator.

Now, University of Wisconsin-Madison engineers have pioneered methods to finance the polymer in these materials using solvents, a technique they call Solvent-Targeted Recovery and Precipitation (STRAP). Proof of them is complete on this day (November 20, 2020) in the journal Advances in Science,

Using a series of solvent washers guided by polymer solubility thermodynamics, UW-Madison professor of chemical and biological engineering George Huber and Reid Van Lehn and his students used the STRAP process to separate polymers in commercial plastics made from common coating materials. polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate.

The results? The separated polymers appear to be chemically the same as those used to make the original film.

The team now hopes to use the recovered polymers to create new plastic materials, suggesting that the process can help close the loop loop. In particular, it can allow multilayer-plastic factories to recover 40 percent of the plastic waste generated during the production and packaging process.

“We have demonstrated this with multilayer plastics,” Huber said. “We need to try different multilayer plastics and we need to scale in this technology.”

As the complexity of multilayer plastics increases, so does the difficulty of identifying solvents that can dissolve each polymer. That is why STRAP relies on a computational approach used by Van Lehn called Screening Models such as Conductors for Realistic Solvents (COSMO-RS) to guide processes.

COSMO-RS can calculate the solubility of target polymers in solvent mixtures at different temperatures, the narrower the number of potential solvents that can dissolve polymers. The team can experiment to explore solvent candidates.

“This allows us to tackle this much more complex system, which is needed if you really want to do recycling in the recycling world,” said Van Lehn.

The goal is to eventually develop a computational system that allows researchers to find solvent combinations to recycle all types of multilayer plastics. The team also hopes to see the environmental impact of working solvents and create a green solvent database that allows them to better balance the effectiveness, cost, and environmental impact of multiple solvent systems.

This project comes from UW-Madison’s skills in catalysis. Over the years, the university’s chemical and biological engineering studies have pioneered solvent-based reactions to convert biomass – such as wood waste or agriculture – into favorable chemicals or advance materials. Most of the expertise was translated into solvent-based polymer recycling as well.

The team is continuing its research in the processing of STRAP through the New Multi-University Center of Chemical Upcycling of Plastics, led by Huber. Researchers at the US $ 12.5 million Department of Energy Department are investigating several chemical pathways for polymer recycling and recycling.

References: November 20, 2020, Advances in Science,

This research is supported by a grant from the U.S. Department of Energy (DE-SC0018409).

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