Breakthrough! Fully recyclable plastics?
Plastics are both a boon and a bane to all humanity. One the one hand, they are strong, light, and flexible. On the other hand, they take centuries to break down, which has created an environmental catastrophe of unimaginable proportions.
Some would argue that plastics have played an important role in powering the robust world economy that has thrived since the end of World War II. Just how central they are to the economic lifeblood of society is made clear in this well known clip from the movie The Graduate.
Scientists at the Lawrence Berkeley National Laboratory say they may have a solution. They have created a recyclable plastic that can be disassembled into its constituent parts at the molecular level. It can then be reassembled into a different shape, texture, and color again and again without loss of performance or quality.
“Most plastics were never made to be recycled,” says lead author Peter Christensen, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry. “But we have discovered a new way to assemble plastics that takes recycling into consideration from a molecular perspective.”
Plastics today are made up of large molecules called polymers which in turn are created from shorter compounds called monomers. Then those polymers are mixed with additives that make them suitable for a particular purpose. Some make a plastic tough. Others make it flexible. Still others change its color. But those additives create strong chemical bonds with the polymers. Breaking those bonds is next to impossible in any cost effective way.
That’s what makes it so hard to recycle plastics. All recycling plants do is chop up all the waste plastic that comes in the door into small bits. When the chopped-up plastic is melted to make a new material, it’s hard to predict which properties it will inherit from the original plastics.
“Circular plastics and plastics upcycling are grand challenges,” says Brett Helms, a staff scientist at Berkeley’s Molecular Foundry. “We’ve already seen the impact of plastic waste leaking into our aquatic ecosystems, and this trend is likely to be exacerbated by the increasing amounts of plastics being manufactured and the downstream pressure it places on our municipal recycling infrastructure.”
The researchers went back to basic principles. This time, instead of inventing plastics that never breakdown, they focused on recyclability from the beginning. The result is a new kind of plastic called polydiketoenamine or PDK. Their report on PDKs has been published recently in the journal Nature Chemistry. “With PDKs, the immutable bonds of conventional plastics are replaced with reversible bonds that allow the plastic to be recycled more effectively,” Helms says.
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. The acid helps to break the bonds between the monomers and separates them from the chemical additives that give plastics their look and feel, according to a report by Science Daily.
“We’re interested in the chemistry that redirects plastic lifecycles from linear to circular,” says Helms. “We see an opportunity to make a difference for where there are no recycling options.” When the monomers are reused to make a new plastic, they are free of the characteristics that gave the original material is color, shape, rigidity, or stretchiness. The monomers become building blocks for new plastics that bear no relationship to the originals. The researchers believe that their new recyclable plastic could be a good alternative to many nonrecyclable plastics in use today.
“We’re at a critical point where we need to think about the infrastructure needed to modernize recycling facilities for future waste sorting and processing,” says Helms. “If these facilities were designed to recycle or upcycle PDK and related plastics, then we would be able to more effectively divert plastic from landfills and the oceans. This is an exciting time to start thinking about how to design both materials and recycling facilities to enable circular plastics.”.
The researchers next 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.
This is great news for a planet strangling in discarded plastic but let’s not let our enthusiasm run away with us here. There are billions of tons of plastics in landfills and the oceans that will take a Herculean effort to clean up. The problem of waste plastic will be with us for decades or even centuries.
While this new research gives us reason for hope, it underscores one of the major imperfections in the capitalist economic model — a failure to plan for managing the waste products of industry. Whether it’s plastics in the oceans, discarded tires in landfills, or carbon dioxide in the atmosphere, the “throwaway” economy that is business as usual today is ultimately self defeating, as it will eventually kill every living thing on the host planet.
Up until now, capitalism has operated on a “privatize the profits and socialize the costs” model. Another way to put is, “Heads, we win. Tails, you lose.” Unless and until the economic model is altered to take into account the costs of a fossil fuel based economy, there is little hope humanity will survive, with or without plastics.
We are fortunate that a possible solution has been found, but let’s not gloss over the fact that the breakthrough comes from an arm of the big bad federal government, which reactionaries always demean as “the problem, not the solution.” In reality, it’s those same reactionaries who are the problem. They clearly are not part of any viable solution.
(Originally appeared at our sister-site, Cleantechnica.)