Plastics are turning up in all the wrong places, from the deepest depths of the ocean to the “pristine” air of the Pyrenees Mountains to even the food we fork into our mouths. It is undeniably a global issue – the world is in need of something more sustainable.
Scientists at the Lawrence Berkeley National Laboratory believe they have made such a state-of-the-art plastic capable of being recycled over and over again with no loss to quality.
“Most plastics were never made to be recycled,” said 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.”
Many plastics have chemicals such as fillers, dyes, or plasticizers that remain even after they've been to a recycling plant. These various plastics – hard toys, flexible materials, clear bags, and so on – can be mixed, ground, and melted to form new materials. However, this medley of plastics makes for an unpredictable outcome, preventing plastic from becoming a truly recyclable resource. Instead, a plastic bag, for example, is incinerated or dumped into a landfill.
“Circular plastics and plastics upcycling are grand challenges,” said team lead Brett Helms, a staff scientist in Berkeley Lab’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 team brainstormed a new solution using a material called poly(diketoenamine), or PDK for short. Here, the monomers – a molecule that can bond with other identical molecules to form a polymer – can be freed from the final plastic by soaking them in a highly acidic solution to break the bonds. Once broken down, these monomers can be built up again and remade into a new polymer design of almost any color, form, or shape.
"Our PDK plastics are an urgent counterpoint. They are made with chemical bonds that are selectively broken using strong acids, returning the original building blocks," said Helms to IFLScience. "We were able to show how these building blocks could be separated from additives commonly added to plastics for aesthetic purposes or performance. Once our building blocks were separated from these additives, we could re-make the same plastic, closing the circular materials lifecycle."
This chemical flexibility allows plastic for a phone case to be broken down and reused for, say, a watch band. Such a material could revolutionize the overwhelming statistics of plastic waste, such as the 5 to 13 million tonnes of plastic that flow into our oceans from coastal areas every year. Not only that, but 1 million plastic bottles are purchased every minute, while 300 million tonnes of plastic waste is produced every year, according to the United Nations Environment. Almost all of this plastic is designed to be used only once and thrown away.
"The success or failure of introducing new plastics into the market, PDK-based or otherwise, will depend on several considerations: the economics of making and manufacturing them; the efficacy of our recycling infrastructure to capture these waste streams for recovery and reuse; and our ability to formulate them to task for specific products, particularly where recycling efforts for those products have failed, such as in food packaging or textiles," said Helms. "While this all sounds convoluted, and it is, it's also an exciting time to be considering what the future of plastics will be."
"Competing against existing plastics is a tough battle. Plastics are cheap," added Christensen to IFLScience "One of the biggest fundamental issues with recycling in general is that the people that make money from selling plastic products aren't the same people that make money from collecting and recycling plastics."
"So, the key to commercializing this, or any other new plastic, is to find the right niche market to look at initially."
"It’s also important that consumers demand products that are designed for recyclability."
Next up, the team is hoping to develop PDK plastics with thermal and mechanical properties for use in textiles, 3D printing, and foams. They are also "making the platform more green and sustainable by making PDK plastics from bio-based feedstocks." The study is published in the journal Nature Chemistry.