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posted by martyb on Thursday May 09 2019, @07:13AM   Printer-friendly
from the "The-Graduate" dept.

Endlessly recyclable plastic (Javascript required.)

By separating plastic monomers from chemical additives, researchers may have created fully recyclable plastics.

Molecular scientists at the Lawrence Berkeley National Laboratory developed a new type of plastic: polydiketoenamine, or PDK. When immersed in an acidic solution, PDK monomers were broken down and were freed from the additive compounds used in plastic production.

Berkeley Lab staff scientist Brett Helms said: "With PDKs, the immutable bonds of conventional plastics are replaced with reversible bonds that allow the plastic to be recycled more effectively."

Commercial plastics generally contain additives such as dyes or fillers to make them hard, stretchy, coloured or clear. The problem is these additives have different chemical compositions and are hard to separate from the monomers.

Also at Berkeley Lab.

See also: Researchers develop plastic that they are calling the 'Holy Grail' of recycling
This infinitely-recyclable plastic might help us finally clean up landfills and oceans

Closed-loop recycling of plastics enabled by dynamic covalent diketoenamine bonds (DOI: 10.1038/s41557-019-0249-2) (DX)


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  • (Score: 1, Interesting) by Anonymous Coward on Thursday May 09 2019, @06:45PM (1 child)

    by Anonymous Coward on Thursday May 09 2019, @06:45PM (#841470)

    Because the energy required to break the polymers into smaller components makes a very low profit commercial application.

    It's a burning process. You just add oxygen.

    But in either case, the purpose of burning properly is not to be economically competitive with gas powered plants that gets its fuel from a pipeline. The purpose is to reduce garbage and harm that it causes. I hope you agree that harm reduction is priority before we can have some panacea solution to this problem?

    TFS gives us academic lego block in solving a tiny portion of the issue. But it does nothing for policy or solution to the plastic problem.

    PVC into the reactor and you'll ruin it and you'll need to install scrubbers; 'cause, you see that ending C? It stands for chlorine - not a nice gas when heated to 800C

    That's true - it's reactive. But this problem is solved, long time ago.

    https://waste-management-world.com/a/pvc-to-burn-or-not-to-burn [waste-management-world.com]

    In conclusion, since the second half of the eighties the problem of reducing emissions of dioxins and organic micro-pollutants has been considered solved at the scientific and technology level. The combination of the following features ensures the reduction of dioxins down to values below the acceptable limits:
    Reaching temperatures of 1100°C Having a post combustor ensuring a contact time of 2 seconds Maintaining an oxygen concentration of 6% in the output gases Ensuring a fast cooling down to 250°C to avoid the 'de novo' synthesis of dioxins Having also a catalyst for destruction of dioxins or a system with adsorbent activated carbon. The Emissions, Recovery and Recycling of Gas

    In addition to hydrochloric acid (which is produced whether PVC is present or not), incinerator emissions also include sulphur and nitrogen compounds.

    During the waste combustion process the rupture of the polymer chain, resulting in the release of chlorine in the form of HCl gas. Even in the absence of PVC, due to other sources such as household chlorine in the waste, combustion will always produce gaseous HCl that must be destroyed prior to the release into the atmosphere.

    It must be emphasised that the removal of HCl gas is facilitated by its chemical characteristics, whereas it is more difficult to remove SOx, which should be blamed as the largest contributor to acid rain. Chlorine also has a positive contribution in flue gas, as it allows better capture of the heavy metals present in MSW waste, thereby reducing emissions into the environment.

    Regarding the influence of the presence of heavy metals in PVC, one should also note that:
    1. The contribution due to the heavy metals in PVC is not significant except for cadmium, which has been phased out
    2. Stabiliser formulations containing heavy metals are used less and less, and are substituted by other chemical substances, which are not hazardous as shown by the Reach Regulations.

    Also, we have technology to monitor these emissions. And as you can see, coal is the problem, not garbage burning.

    https://earth.nullschool.net/#current/chem/surface/level/overlay=so2smass/orthographic=-78.02,25.18,427 [nullschool.net]

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  • (Score: 2) by c0lo on Thursday May 09 2019, @10:33PM

    by c0lo (156) Subscriber Badge on Thursday May 09 2019, @10:33PM (#841577) Journal

    It's a burning process. You just add oxygen.

    Pyrolysis [wikipedia.org] is not burning.

    Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere

    ---

    But in either case, the purpose of burning properly is not to be economically competitive with gas powered plants that gets its fuel from a pipeline.

    I don't object to the purpose, I objected to the Plastic burns just as well as any oil.. It si,pl;y doesn't.
    And, coming to harm-reduction: lowering the reliance on platics, especially single use plastic, sounds like a better proposition - less need to collect and deal with it.

    --
    https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford