Saturday, May 28, 2022

A new kind of plastic that maintains its original qualities when recycled

High-performance circular polymers with both intrinsic chemical recyclability and crystallinity.

The failure to address end-of-life issues of today’s plastics has not only accelerated the depletion of finite natural resources but also caused severe worldwide plastics pollution problems. Because of that, scientists have been hard a work looking for a new kind of plastic that has all the advantages of the old plastic but also can be easily recycled.

In a new study, scientists reported having developed such plastic that can maintain its original qualities when recycled.

Scientists developed this plastic by setting up a bridged bicyclic thiolactone monomer from a bio-based olefin carboxylic acid. The outcome was a plastic (they called PBTL) that had all the characteristics of traditional plastics. They next tested their plastic by conducting bulk depolymerization at 100°C using a catalyst.

MALDI-TOF MS and viscosity
Determination of topology by MALDI-TOF MS and viscosity. (A) MS spectrum and plot of mass/charge ratio (m/z) values versus the theoretical number of M repeat units for the linear PBTL produced by IMes and BnOH. (B) MS spectrum and plot of m/z values versus the theoretical number of M repeat units for the cyclic PBTL produced by IMes alone. (C) Double logarithm (Mark-Houwink) plots of intrinsic viscosity [η] versus Mw of the linear (blue line) and cyclic (red line) PBTL samples produced by IMes with BnOH and without BnOH. Inset: a photograph of isolated cyclic PBTL. Credit: Science Advances (2020). DOI: 10.1126/sciadv.abc0495

Testing of the result showed the PBTL had been broken down into its original monomer. They followed that up by breaking down samples of PBTL (using a catalyst) at room temperature. And once again, close examination showed the sample had been broken down to the original monomer.

Using the monomers from both processes to make new batches of PBTL, scientists proved that the new plastic could be created, broken down, and created again—over and over. 

Scientists noted, “The process could be repeated indefinitely. They further suggest that their new plastic could make a host of products now made using conventional plastics—greatly reducing the number of plastics that end up in the environment. The only caveat in the scenario is that such plastics would have to be separated from other materials before they could be recycled.”

Journal Reference:
  1. Changxia Shi et al. High-performance pan-tactic polythioesters with intrinsic crystallinity and chemical recyclability, Science Advances (2020). DOI: 10.1126/sciadv.abc0495
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