Is PDK a resin of the future?

Researchers affiliated with the Lawrence Berkeley National Laboratory in Berkeley, California, say momentum is growing for the wider adoption of a new plastic resin that “has all the convenient properties of traditional plastics [and] can be recycled indefinitely with no loss in quality.”

Two years ago, a Berkeley Lab research team led by Brett Helms announced the invention of poly diketoenamine (PDK), which it said could be “disassembled into its constituent parts at the molecular level, and then reassembled into a different shape, texture and color repeatedly without the loss of performance or quality.”

As investments in chemical recycling are being increasingly made in the United States and globally, Helms and a team of fellow researchers that includes Corinne Scown, Jay Keasling and Kristin Persson have released a study they say shows “PDK-based plastic could quickly become commercially competitive with conventional plastics, and the products will get less expensive and more sustainable as time goes on.”

“Plastics were never designed to be recycled,” says Nemi Vora, who worked with Scown on the report. “The need to do so was recognized long afterward. But driving sustainability is the heart of this project. PDKs were designed to be recycled from the get-go, and since the beginning, the team has been working to refine the production and recycling processes for PDK so that the material could be inexpensive and easy enough to be deployed at commercial scales in anything from packaging to cars.”

The study presents a simulation for a 20,000-metric-tons-per-year facility that creates new PDK resins after taking in mixed PDK scrap for chemical recycling. The authors say they calculated the chemical inputs and technology needed, as well as the costs and greenhouse gas emissions, then compared their findings to the equivalent figures for the production of conventional plastics.

“These days, there is a huge push for adopting circular economy practices in the industry,” says Vora. “Everyone is trying to recycle whatever they’re putting out in the market. We started talking to [companies] about deploying 100 percent infinitely recycled plastics and have received a lot of interest.”

While PDK plastics likely could be recycled mechanically, their design makes them ideal for the chemical recycling process. The resin’s polymers “are engineered to easily break down into individual monomers when mixed with an acid,” says Berkeley Lab.

“The monomers can then be separated from any additives and gathered to make new plastics without any loss of quality,” state the researchers. The team’s earlier research shows that this chemical recycling process “is light on energy and carbon dioxide (CO₂) emissions, and it can be repeated indefinitely, creating a completely circular material life cycle.”

Scown says of the main findings of the new report, “The main takeaways were that, once you’ve produced the PDK initially and you’ve got it in the system, the cost and the greenhouse gas emissions associated with continuing to recycle it back to monomers and make new products could be lower than, or at least on par with, many conventional polymers.”

Berkeley Lab says PDKs are already drawing interest from companies that need to source plastic, with initial markets possibly being in the automotive and consumer electronics sectors. “We’re bringing in partners who are building circularity into their product lines and manufacturing capabilities, and giving them an option that is in line with future best practices,” says Helms.

Berkeley Lab describes itself as a multiprogram national laboratory managed by the University of California for the U.S. Department of Energy’s Office of Science.