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UNC Researchers Develop Method to Create a Better Plastic

The United States generates more plastic trash than any other country—about 46.3 million tons of it or 287 pounds per person a year, according to a 2020 study.

The country’s 9% rate of recycling will never keep up. Why so low? The chemistry of today’s plastics makes most difficult to recycle. Even thermoplastics that can be melted down weaken with each re-use. And that leads to the real barrier to recycling—economics. There’s just no profit incentive.

But a group of chemists at the University of North Carolina at Chapel Hill, a Sullivan Foundation partner school, have turned the tables by discovering a method to break down plastics to create a new material that is stronger and tougher than the original—meaning it’s potentially more valuable.

Related: William & Mary initiative challenges Virginia kids to solve microplastic pollution problem

“Our approach views plastic waste as a potentially valuable resource for the production of new molecules and materials,” said Frank Leibfarth, assistant professor of chemistry in the UNC College of Arts & Sciences.  “We hope this method could drive an economic incentive to recycle plastic, literally turning trash into treasure.”

Leibfarth and UNC-Chapel Hill professor Erik Alexanian, who specializes in chemical synthesis, describe the approach that could close the loop on plastic recycling in the journal Science.

Carbon-hydrogen bonds are some of the strongest chemical bonds in nature. Their stability makes it difficult to turn natural products into medicines and challenging to recycle commodity plastics.

But by modifying the carbon-hydrogen bonds that are common in polymers—the building blocks for modern plastic used in grocery bags, soda and water bottles, food packaging, auto parts and toys—the life span of polymers could be expanded beyond single-use plastic.

Related: The Plastic Bank turns plastic waste into currency for the poor

With a newly identified reagent that can strip hydrogen atoms off medicinal compounds and polymers, the UNC chemists were able to make new bonds in places previously considered unreactive.

“The versatility of our approach is that it enables many valuable transformations of carbon-hydrogen bonds on such a wide range of important compounds,” Alexanian said.

The Leibfarth Group at UNC is focused on designing polymers that are smarter, more functional and more sustainable. With the support of the NC Policy Collaboratory, the team developed a super-absorbent polymer capable of removing dangerous chemicals from drinking water.

Researchers envisioned using the innovative approach to help transform difficult-to-recycle plastic waste into a high-value class of polymers. They started with plastic foam packaging used to protect electronics during shipping, materials which otherwise end up in landfills. Samples of post-consumer foam were provided by High Cube LLC, a Durham, N.C., recycling company. The foam is made of a low-density plastic called a commercial polyolefin.

By selectively pulling hydrogen atoms from polyolefin, the chemists came up with a way to expand the life of the single-use plastic into a high-value plastic known as an ionomer. Popular ionomers are Dow’s SURLYN, a go-to material used in a wide variety of food packaging.

Related: UNC research explains why sea turtles eat plastic

Most recycled plastic is “downcycled” into lower quality products like carpet or polyester clothing. This material may still end up in landfills. Discarded plastics in waterways endanger sea life if, for example, turtles mistake ocean plastic for food.

But if the chemistry can be repeatedly applied to polymers to help recycle them over and over again, “it could change the way we look at plastic,” Leibfarth said.

Study co-authors include Timothy Fazekas, Jill W. Alty, Eliza K. Neidhart and Austin S. Miller.

The National Institute of General Medical Sciences, the Air Force Office of Scientific Research, the National Science Foundation and the UNC Department of Chemistry funded the study.

This article has been edited slightly from the original version appearing on the University of North Caroline-Chapel Hill website.

 

Researchers Have Found a Better Way to Recycle Polyurethanes

Researchers at the University of Minnesota are part of a national team in the Center for Sustainable Polymers that has found a better way to recycle a versatile plastic material, called polyurethanes, that could prevent the material from becoming waste, according to a press release.

In the past, a few methods have attempted to recycle polyurethane waste, but these techniques result in a material of lower quality. Now, researchers have found a way to recycle used polyurethanes into equivalent or even higher quality material using an innovative method.

Their findings are reported in the journal ACS Central Science, published by the American Chemical Society.

Related: The Plastic Bank turns plastic waste into currency for the poor

“We are quite excited about this new research from the Center for Sustainable Polymers because of the tremendous potential for recycling of polyurethane materials that are typically considered as waste,” said Marc Hillmyer, director of the Center for Sustainable Polymers based at the University of Minnesota and a chemistry professor at the University of Minnesota. “It also demonstrates how the powerful combination of polymer chemistry and polymer processing can be applied to help solve environmental problems.”

Polyurethanes are all around us. Polyurethanes can be a found in mattresses, insulation, footwear, construction materials, automotive suspension systems, carpet underlay, and many other products. Wear and replacement of these products generates a lot of waste and creates demand for new polyurethanes, often made from toxic chemical building blocks.

Conventional polyurethanes can’t be simply recycled by heating because the material consists of polymer networks held together by strong chemical bonds that don’t flow when heated. Instead, polyurethanes can only be downcycled into less useful materials using either mechanical methods or chemical recycling. Other past methods have made innovative types of polyurethanes with cross-links that can be broken and reformed, allowing it to be recycled. But this approach requires the industry to commercialize new starting materials, and it wouldn’t address the issue of conventional waste lingering in landfills. These methods also haven’t been tested on foams, a very common form for polyurethane products.

Related: This bioplastics entrepreneur is helping save the world from plastic waste

In this new study, researchers from the University of Minnesota and Northwestern University ground up polyurethane foam or film and then mixed the particles in a catalyst solution. After drying, the particles were compression molded to form new films. Compression molded films formed good-quality products, but compression molded foam produced cracked and inhomogeneous materials.

The researchers solved this problem by developing a twin-screw extrusion process that improved mixing and air removal in recycled foams, compared to the compression molding approach. They say this new method could be used for continuous recycling of the large amounts of polyurethanes waste currently in landfills and newly produced.

“The extrusion process removes air simultaneously as the catalyst enables the polyurethane to flow like a liquid,” said Christopher Ellison, a University of Minnesota chemical engineering and materials science professor and one of the senior authors of the study. “This reactive process is similar to those already used in the plastics industry for other purposes meaning the technology could have impact quickly.”

 

The Plastic Bank Turns Plastic Waste into Currency for the Poor

If you thought plastic waste was good for nothing except polluting our oceans and hogging space in landfills, think again. A Canadian social enterprise, the Plastic Bank, has turned it into currency, empowering individuals in impoverished developing countries to combat plastic pollution while earning money or credit.

Based in Vancouver, Canada, and founded in 2013 by David Katz and Shaun Frankson, the Plastic Bank pays people in Haiti, Indonesia, Brazil and the Philippines to collect plastic waste and bring it to collection centers operated by the Plastic Bank. There, the trash is weighed and checked for quality, and collectors receive money for their work, or the value of the plastic can be transferred via a mobile Blockchain app into a digital bank account for each collector.

Related: Bioplastics entrepreneur Julianna Keeling is helping save the world from plastic waste

The collectors can use the credit to pay for school tuition, medical insurance, WiFi, cellphone minutes, Internet access, cooking fuel, electricity and other essentials. They can also borrow against their credit, according to Katz.

The Plastic Bank’s collection centers also offer fresh food—most of it locally sourced and high in nutrition—and clean drinking water in exchange for collected plastic.

The Plastic Bank’s locally operated recycling centers turn the collected plastic into pellets that are resold to companies like the UK’s Marks & Spencers and consumer goods company Henkel in Germany. These companies repurpose the plastic to manufacture products made from what is termed Social Plastic. Social Plastic products include Henkel’s Nature Box Shampoo & Shower Gel and FA Shower Gel, the Spooked Kooks brand of foam surfboards in Australia, and eco-shopping bags produced by Marks & Spencers.

Related: Eager to create social change in your community? Join us for the Sullivan Foundation’s Ignite Retreat March 27-29 in Wake Forest, N.C.

According to Plastic Bank’s website, its collectors have thus far recovered more than 18.7 million pounds of ocean-bound plastic.

this is a photo of a man sorting through plastic waste for the Plastic Bank

The Plastic Bank monetizes plastic waste while helping people in impoverished countries build a fair and steady income.

“Now we’ve closed the loop in our circular economy,” Katz said in a Ted Talk (see video). “Now, buy shampoo or laundry detergent that has Social Plastic packaging, and you are indirectly contributing to the extraction of plastic from ocean-bound waterways and alleviating poverty at the same time. And that model is completely replicable.”

At the Plastic Bank’s home base in Vancouver, individuals or groups can also bring in deposit-refundable recyclable plastic, Katz says. “And instead of taking back the cash, they have the opportunity to deposit that value into the accounts of the poor around the world. We can now use our recycling to support and create recyclers.”

Related: Ignite Retreat speaker leads charge to reduce plastic waste in Durham, N.C.

In addition to providing a fair and steady income for collectors, the social enterprise’s recycling centers provide fulltime jobs, with managers earning up to $3,000 a year after paying their employees and other expenses, according to Global Citizen. That’s a significant income boost in a country like Haiti, where the majority of people live on under $2 a day.

As of November 2019, there were 20 Plastic Bank recycling markets operating in Haiti, where vast quantities of plastic waste litter the streets and shorelines and end up in waterways and, finally, the ocean.

this photo shows another Plastic Bank employee hard at work

The Plastic Bank operates plastic waste collection centers in Haiti, Indonesia, Brazil and the Philippines.

“Millions of people around the world already rely on ‘waste picking’ to sustain their living, and as a result, are marginalized and stigmatized by the rest of society,” Katz says. “By working to formalize their employment and paying premiums far and above their usual market rates, the Plastic Bank aims to reverse this pejorative characterization and acknowledge these citizens for the environmental champions they are.”

Katz also urges consumers to voice their displeasure with single-use plastic to companies that are adding to the plastic waste problem. “Every time you buy something with excessive plastic, every time you buy something with single-use plastic, you are voting for that to continue,” he told Public Radio International. “If you have some ambition about changing what is occurring in the ocean, then participate. There is a complete social media department at every one of those manufacturers and every one of those brands. They’re listening. So, reach out to them, tweet to them, email them. Let them know that you won’t stand for it and let them know that you want alternative packaging. They listen, and they will eventually provide what customers want. That’s what they do.”

Related: Edible bowls and plates could take a bite out of plastic waste