Who

Anyone who uses products made of plastic. The new recyclable plastic could be a good alternative to many nonrecyclable plastics in use today.

What

PDK plastic degrades in acid to its molecular building blocks. (Peter Christensen/Berkeley Lab)

All plastics — from water bottles to automobile parts — are made up of large molecules called polymers, which are composed of repeating units of shorter carbon-containing compounds called monomers. During processing at recycling plants, plastics with different chemical compositions are mixed together and ground into bits. When chopped-up plastic is melted to make a new material, it’s hard to predict which properties it will inherit from the original plastics. This has prevented plastic from becoming a “circular” material whose original monomers can be recovered for reuse for as long as possible, or “upcycled” to make a new, higher-quality product. The new plastic, called poly(diketoenamine), or PDK, can be disassembled into its constituent parts at the molecular level and then reassembled into a different shape, texture, and color again and again without loss of performance or quality. With PDKs, the bonds of conventional plastics are replaced with reversible bonds that allow the plastic to be recycled more effectively. Unlike conventional plastics, the monomers of PDK plastic could be recovered and freed from any compounded additives simply by dunking the material in a highly acidic solution. The acid helps to break the bonds between the monomers and separate them from the chemical additives that give plastic its look and feel.

PDK plastics are a “circular” material whose original monomers can be recovered for reuse for as long as possible, or “upcycled” to make a new, higher-quality product. (Peter Christensen et al./Berkeley Lab)

Where

Lawrence Berkeley National Laboratory, Berkeley, CA

Why

Very few plastics can be recycled without loss in performance or aesthetics. Even the most recyclable plastic, poly(ethylene terephthalate), or PET, is only recycled at a rate of 20 to 30%, with the rest typically going to incinerators or landfills where the carbon-rich material takes centuries to decompose.

When

The researchers plan to develop PDK plastics with a wide range of thermal and mechanical properties for applications as diverse as textiles, 3D printing, and foams. In addition, they are looking to expand the formulations by incorporating plant-based materials and other sustainable sources. The technology is available for licensing and collaboration.

Tech Briefs Magazine

This article first appeared in the July, 2019 issue of Tech Briefs Magazine.

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