As most environmentally conscious people know, due to various additives present in most plastics only a fraction (about 9 per cent) of them get recycled, which is one of the reasons why industry has lately been attempting to shift away from plastic altogether.
In contrast, a group of researchers from the Molecular Foundry at the Lawrence Berkeley National Laboratory have taken a different approach, namely – the development of a type of plastic suitable for closed-loop recycling.
The new invention – called poly(diketoenamine) or PDK – can undergo reversible polymerisation, which allows for the recovery of high-value monomers that can be used for producing new materials without losing anything in terms of quality or performance.
“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.”
The key issue in recycling plastics is the aforementioned additives – since different compounds are added to plastics to give them different properties, once they’re melted together at a recycling plant, it becomes impossible to predict the qualities of the resulting product.
PDK, on the other hand, can be simply dunked in a highly acidic solution which breaks down the chemical bonds between monomers and separates them from the additives responsible for the specific qualities of different plastics.
“We’re interested in the chemistry that redirects plastic lifecycles from linear to circular,” said co-author Brett Helms. “We see an opportunity to make a difference for where there are no recycling options.”
The team even managed to demonstrate that the “liberated” monomers can be joined back into polymers and entwined with any type of additive, depending on the desired qualities of the end-product. PDK is even permissive of upcycling, which refers to reusing old plastics to make higher quality materials.
Next, the research team will attempt to produce PDKs with a variety of different thermal and mechanical properties, as well as incorporate plant materials into their formulas to improve the sustainability of the new material even further.
The study was published in the journal Nature Chemistry.