University of Michigan researchers discover way to recycle PVC plastic

Plastic recycling on conveyor belt at recycling centre. (Photo by Damian Gillie/Construction Photography/Avalon/Getty Images) (Construction Photography/Avalon, Construction Photography/Avalon)

ANN ARBOR – PVC, or polyvinyl chloride, is a prevalent plastic in the United States and is the third highest plastic produced in the world by volume.

We encounter PVC every day, since numerous household materials like flooring, housing trim, window frames and siding are made of, or include, the plastic.

Additionally, PVC is the primary plastic used in modern plumbing piping and hospital equipment like blood bags, masks, tubing and more. It is used to coat electrical wiring and can also be found in clothing, curtains, tarps and tents.

The recycling rate for PCV in the U.S. is 0%, since it releases dangerous chemicals when exposed to heat.

But one team of researchers at the University of Michigan say they have found a way to recycle the material by chemically breaking it down.

Led by Danielle Fagnani and Anne McNeil, the team discovered that phthalates can act as a mediator for the chemical in the plasticizers -- the plastic’s most noxious components.

“PVC is the kind of plastic that no one wants to deal with because it has its own unique set of problems,” Fagnani said in a statement. “PVC usually contains a lot of plasticizers, which contaminate everything in the recycling stream and are usually very toxic. It also releases hydrochloric acid really rapidly with some heat.”

Plastic is typically recycled mechanically by being melted down and reformed into lower quality materials. As Fagnani mentioned above, when PVC is heated its plasticizers quickly leach out toxic materials like hydrochloric acid, an agent that can cause chemical burns and corrode recycling equipment.

Additionally, phthalates, commonly used as a plasticizer, are highly toxic and can disrupt the endocrine system in mammals, including people, by interfering with growth hormones, the thyroid hormone and reproductive hormones.

To avoid a heat-based recycling process for PVC, Fagnani turned to electrochemistry. She and the team found that phthalates -- a plasticizer itself -- can both successfully break down PVC and significantly slows the release of hydrochloric acid.

Fagnani hopes their findings will inspire other scientists to recycle other difficult materials using chemical reactions.

“Let’s be strategic with the additives that are in plastics formulations. Let’s think about the during-use and end-of-use from the perspective of the additives,” said Fagnani in a statement. “Current group members are trying to improve the efficiency of this process even more.”

Chemically recycling plastics is the focus of McNeil’s lab at U-M.

“It’s a failure of humanity to have created these amazing materials which have improved our lives in many ways, but at the same time to be so shortsighted that we didn’t think about what to do with the waste,” McNeil said in a statement. “In the United States, we’re still stuck at a 9% recycling rate, and it’s only a few types of plastics.

“And even for the plastics we do recycle, it leads to lower and lower quality polymers. Our beverage bottles never become beverage bottles again. They become a textile or a park bench, which then ends up in a landfill.”

Read the full study: Using waste poly(vinyl chloride) to synthesize chloroarenes by plasticizer-mediated electro(de)chlorination


About the Author:

Meredith has worked for WDIV since August 2017 and was voted one of Washtenaw County's best journalists in 2019 by eCurrent's readers. She covers the community of Ann Arbor and has a Master's degree in International Broadcast Journalism from City University London, UK.