Wednesday, 24 July, 2019

Breakthrough discovery: New plastic can be fully recycled again and again

Closed Loop Plastics Source Peter Christensen | Brett Evans | Angelique Scheuermann | Kathryn Loeffler Berkeley Lab
Sandy Nunez | 11 May, 2019, 14:42

This inheritance of unknown and therefore unpredictable properties has prevented plastic from becoming what many consider the Holy Grail of recycling: 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.

A group of scientists at the U.S. Bureau of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) has structured a recyclable plastic that can be dismantled into its constituent parts at the sub-atomic dimension, and after that reassembled into an alternate shape, surface, and shading over and over without loss of execution or quality.

"Most plastics were never made to be recycled", said lead author Peter Christensen, a postdoctoral researcher at Berkeley Lab's Molecular Foundry, in a statement. But a new discovery offers hope, and could revolutionize the way we deal with plastic. Called poly (diketoenamine), or PDK, the new material could help unblock the plastic pileup at recycling plants and ease ocean pollution that could be sucking $2.5 trillion from sectors including fisheries, tourism, and human health, according to one study.

The new plastic this team has cooked up - what they're calling called polydiketoenamine, or PDK - could make recycling more appealing because all that's needed is some acid to separate its chemical additives from the monomers. "That broken black watchband you tossed in the trash could find new life as a computer keyboard if it's made with our PDK plastics".

Unlike conventional plastics, the monomers of PDK plastic can be recovered and freed from any additives simply by dunking the material in a highly acidic solution. "Poly (diketoenamine) s "click" together from a wide variety of triketones and aromatic or aliphatic amines, yielding only water as a by-product", the researchers wrote in their study.

The chemicals added to make them useful-fillers for toughness, plasticizers for flexibility-tend to stay in place even after the material has been processed at a recycling plant.

A by-product of petroleum, plastic is made up of molecules known as polymers that are composed of carbon-containing compounds known as monomers.

Thus, when plastics are processed to create new materials, it is hard to predict which properties the new material will inherit from the original plastics.

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If all goes well, we could be on the verge of a plastic revolution.

Right now, this plastic only exists in the lab. Often, the plastic won't be as durable in its next life.

Helms noted that, if facilities were created to recycle or upcycle PDK, it would be easier to divert plastic from landfills and the oceans. Some make a plastic tough.

"We see an opportunity to make a difference for where there are no recycling options", Helms added, advocating for the modernization of recycling facilities.

Around 700,000 plastic bottles a day end up as litter.

Plastic recycling figures are trending down, making breakthroughs in recyclable plastic all the more important. Their report on PDKs has been published recently in the journal Nature Chemistry.

To the eternal confusion of consumers everywhere, some of those plastics can be broken down into components and recycled relatively easily.