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Reycling Plastic from the Inside Out
- jagger27 8y ago"Unlike conventional plastics, the monomers of PDK plastic could be recovered and freed from any compounded additives simply by dunking the material in a highly acidic solution. The acid helps to break the bonds between the monomers and separate them from the chemical additives that give plastic its look and feel." Anyone know if any acid will work or if the solution is somehow special? Sounds like a big downside to lose acid resistance.
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- HillRat 8y agoLooks like they use sulfuric acid at 0.5 to 5 M over a 24-hour period to depolymerize the plastics. So highly acidic, but probably better to keep your acids in polyethylene containers!
- maliker 8y agoThis is probably a dumb question, but what essential products use plastics and for which no other material is an adequate substitute for the plastic components?
- waiseristy 8y agoThere are an innumerable amount of products that would either be impossible to produce, unsafe to use, or expensive and wasteful without plastics
- ehnto 8y agoThat only changes the question to "are these products worth it?". I would argue there is a huge portion of consumer products that only use plastic because it is cheaper and the negatives of plastics were not in the equation at all.
- learnstats2 8y agoBut what would you be using instead and why would that material not have broadly similar negatives?
- ehnto 8y agoIt vastly depends on the product, but it is a question worth asking over and over again when we design products. It has historically been plastic because it is cheap and readily altered to match the exact needs of the product. Rigid, soft, rugged, smooth, coarse, we can make a plastic suit. Plastic cups are a good example, we have numerous materials at our disposal but we make disposable cups and containers out of plastic. Even bio-degradable plastic cups are a bad choice of material, as they take special circumstances to break down that many municipalities don't provide for and most users aren't carrying their bio degradable cups home to put in their compost. If they end up in the ocean, they will last just as long as other plastics. So that is bad product design, it doesn't take the full product lifecycle into account and ignores even it's typical usage of just a single serve drink used once. Plastics have spoiled us too, so in many cases there probably isn't an alternative that is just as good. We may just have to accept that and find ways to make better materials out of more sustainable sources.
- learnstats2 8y agoYes - I've also heard criticism of bio-degradable plastic cups from environmental groups. But, I missed it if you said it - what material should we ideally use for disposable cups, currently?
- ehnto 8y agoI would personally pick paper for single use cups. It is not perfect, still quite resource intensive to make and still unlikely to be recycled properly. But they can at least be sustained through sustainable forestry and the waste will degrade in the most likely places it will end up.
- ahje 8y ago
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- inflatableDodo 8y agoThe medical field comes immediately to mind, from implants through to flexible tubing. I mean, I suppose you could make the tubing for a peristaltic pump from cat gut or something.
- chrisbrandow 8y agoIt’s not just “can be made”, but “can be made remotely as inexpensively or as easily”
- TehCorwiz 8y agoLots of medical and lab supplies, such as tubing, tools, and stents. For some applications glass is too fragile, metal can be too reactive. Even "inert" metals like titanium or nickel eventually develop bio-films. Various plastics' combination of temperature stability at both high and low temps (cryo / autoclave), non-bio-reactivity (body doesn't attack or reject over short spans), and corrosion resistance makes plastics perfect for these situations. Especially wet situations. And since plastics can be fine tuned for application specific needs they can be iterated on quickly with a materials but not manufacturing process change in some cases. My wife and I had this conversation a couple weeks ago asking this very question which ultimately boils down to: "Are plastics worth it at all ever?" And the answer we found, surprisingly, was yes. edit: a typo.
- phkahler 8y agoAren't plastics usually reasonable to burn as well? As in burning mostly produces CO2 and water? Or do common plastics contain some nasty atoms we dont want in the air in any way?
- TehCorwiz 8y agoPlastics often are doped with heavy metals like molybdenum to affect mechanical properties like wear resistance, or bromine for fire resistance. Neither of which you want in your lungs.
- ghjjjj 8y agoEven putting aside the heavy metals, the assumption that they burn into CO2 is a hard one to accomplish in fact. Done improperly, you end up with a very snokey, sooty smoke. Done properly, you’re dealing with very high T, which is hard, and NOx production. But, assuming you’re doing a good job... burn baby burn! (Just separate out the per-fluorinates - HF is nasty)
- code_duck 8y agoThey can be burned safely in an incinerator. Ad hoc burning can produce very toxic chemicals, though, including dioxins, hydrogen cyanide, vinyl chloride and furans. It could release lead. It depends on the type of plastic (PVC? Polyethylene? Polypropylene?). This is why it’s troubling to see people burning bags of trash and tossing in plastic bags and soda bottles as if they magically disappear. This is a good rundown: https://www.directplastics.co.uk/about_plastics/post/whats-in-those-fumes https://www.directplastics.co.uk/about_plastics/post/whats-i... MIT says... https://engineering.mit.edu/engage/ask-an-engineer/can-we-safely-burn-used-plastic-objects-in-a-domestic-fireplace/ https://engineering.mit.edu/engage/ask-an-engineer/can-we-sa... “When plastic is burned, it releases dangerous chemicals such as hydrochloric acid, sulfur dioxide, dioxins, furans and heavy metals, as well as particulate.”
- munk-a 8y agoAs some siblings have pointed out there are specific uses plastics are good for - and I don't think the goal should be to reduce plastic usage to zero. I think it's more important to go after stupid consumer product usages of plastic that are unnecessary, a moderate amount of plastic use and reuse is totally reasonable and sustainable, when we have half the mass being tossed away in the form of clamshells then we have an issue.
- reaperducer 8y agoI agree. Yesterday the IT department brought me a big box of USB hard drives. I spent an hour unpacking them and after setting the recyclable cardboard aside was left with a mountain of plastic shells that were used for shock absorption and peg hangars. IMO, there's no reason these couldn't have been made of cardboard as well.
- ghjjjj 8y agoNormal plastics (or polymers) aren’t all that bad. Some fish will choke on it and that’s terrible, sure. But, if you want a real environmental shit-show read up of per fluorinate manufacturing. Teflon, gore Tex, etc is the real deamon children of the polymer industry.
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- dsfyu404ed 8y agoif your definition of "adequate" includes a price component than a heck of a lot of things.
- trickstra 8y agoExactly this. We must not forget how stupidly cheap it is to make something from plastic before we start making bags, cups and straws out of paper. The great thing about plastics is their high durability and low cost of production. The main problem with plastics is their high durability and low cost of production.
- pkaye 8y agoI have kidney dialysis daily and there is quite a bit of stuff for which plastic is most suitable.
- TeMPOraL 8y agoThere are few things that couldn't possibly be done without plastic, but most of things do benefit from being plastic to various degree. People mention various material properties crucial to medical use, but I'd mention a simple other one: mass. If you tried to replace plastics with metals and glass in consumer products while retaining similar material properties, you'd end up with a lot heavier products. Think e.g. plastic bottle vs. glass bottle for an obvious example. All that mass increases fuel used whenever you have to move it. This alone doesn't justify use of plastics everywhere, but it does matter at scale and over lifecycles of some products, so it's worth remembering.
- ricardobeat 8y agoAluminium has similar weight to volume ratio for small applications, and is the easiest to recycle, but is not aesthetically pleasing. Hopefully something like ALON (transparent aluminium ceramic) could come to the consumer market at some point?
- aetherspawn 8y agoI think Al is bad for you when it comes to handling food. I’ve heard that aluminium pots and pans, as well as traces in things like salt, are strongly linked to Alzheimer’s.
- FreeFull 8y agoThis is why aluminium drinks cans have a lining of plastic on the inside. So even with aluminium containers, you don't get away from plastic.
- ricardobeat 8y agoTrue, and the original lining ended up being banned as an endocrine disruptor (BPA). I’d guess the lining is more for protecting the integrity of the metal than food safety. A middle-ground alternative would be returning to glass once transportation is fully electric and based on clean energy. Still lots of downsides, not an easy problem to solve.
- dredmorbius 8y agoA very good question, actually, and one which gets to the heart of materials science. Which is nowhere near my areas of expertise, though I've been looking into this incidental to other interests. Meta-answering by way of what the pre-plastic world looked like.... The history of the study itself is interesting: materials science & engineering grew mostly out of mining engineering, which subsumed metallurgy (see Agricola's De Re Metalica, still a leading text through the early 20th century, or the evolution of M.I.T.'s course catalogue), but picked up other elements (so to speak) especially with the rise of coal-tar and petroleum (organic) chemistry. There was the golden age of plastics, roughly 1920-1940, when many modern polymers were invented (polystyrene, polyester, PVC, Nylon, etc.). Earlier, ~1840s-1890s rayon and celluloid (from plant fibres) and bakelite (coal tar). Vaclav Smil has an excellent book on materials, Making the Modern World, which looks at sourcing and usage (https://www.worldcat.org/title/making-the-modern-world/oclc/868348464 https://www.worldcat.org/title/making-the-modern-world/oclc/...). Strongly recommended. You can look at what materials were used before plastics were available. Early 20th century children's toys were often made of stamped tin. Wood, woven fibres or reeds (baskets, wicker or rattan furniture), fabrics, hides, metals, and stone, were commonly used. Plastics replaced many of these on the basis of cost, weight, flexibility, mouldability, process-scalability, automation, and frequently durability, as well as water-, air-, and rot-resistance. Human use of materials gives a strong sense of time. In film and theatre, much of the atmosphere of an era, beyond mere styling, derives from the materials used or incorporated: stone, brick, plaster, ceramics, wood, fibres, dyes, glass, metals, and synthetics. Mid-century US clothing is dominated by wool and leather, the 1960s mood is set by synthetcs and plastics, 1970s by polyester. Since then there's been a movement back to more natural fabrics generally, though nylon outerwear cold-weather garments are still popular. Many of the shifts in material use are energy-bounded. Not merely in processing (metals smelting, glass and ceramics production), but in transport and sourcing. Paris's catacombs, I've just learned, were largely formed as quarries for building materials. Almost all pre-modern construction used locally-sourced materials, or materials which could be moved nearly entirely by water, with minimal thermal processing. Lumber use was historically minimised due to its scarcity -- half-timbered and full-brick or stone construction limit wood use for a few weight-bearing members, and fill planes and voids with more-abundant materials -- stone, wattle-and-daub, lathe-and-plaster, brick, even straw. (Fire risk was another consideration restricting wood construction in pre-modern cities.) Whilst the US had vast forests at its founding, they were largely consumed within about a century, for both construction and fuel. Despite its coal riches, wood use exceeded coal through the 1880s. (Oil surpassed coal only in the 1950s.) With coal, steam, rail, excavators, drilling rigs, pipelines, and tankers, sourcing vast amounts of coal and oil from inconvenient remote locations and synthesizing useful fabrication and construction materials became possibe. Voila: Plastic age. Metal mining, refining, smelting, and founding also advanced rapidly -- highly-reliable, high-power locomotives, rails, pipelines, and steamships were infeasible prior to Bessemer steel (1860s). Aircraft required aluminium structural members and fuselage panels (1880s). So there's a complex bootstrap process involved. (This isn't a defence of plastics, just a brief, very rough, and non-expert materials/economic history.)
- fredgrott 8y agoanyone that has a breathing issue uses plastic in all the hose connections up to the oxygen machine...my Father uses such a machine and those tubes regularly fail after awhile and need replacing..I usually get the job of replacing them..
- inflatableDodo 8y agoLook as though the polydiketoenamines themselves are also quite easy to make; >"Surprisingly, polydiketoenamines could be made simply by mixing ketones and amines. ‘It’s a click reaction that works at room temperature, without needing catalysts, additives or even a solvent,’ says Helms. ‘They just require a few minutes in a ball mill.’" https://www.chemistryworld.com/news/new-family-of-polymers-can-be-easily-recycled-and-even-upcycled/3010439.article https://www.chemistryworld.com/news/new-family-of-polymers-c...
- stevespang 8y agoHmmm, last I checked concentrated sulfuric acid is not commonly available to or advised to be used by the public . . . so forget about the common man recycling this stuff, just another development of "big corporate" to keep this product and the system surrounding it all within their clutches. On the other hand, my son and I just filed a patent for a low melt temp polymer system that is flexible, recyclable merely with low heat, biodegradeable (without acids), repurposeable, NON TOXIC, and all processes can be done at home safely by the public, no corporate involvement necessary.
- cr0sh 8y ago> Hmmm, last I checked concentrated sulfuric acid is not commonly available to or advised to be used by the public IIRC, lead-acid batteries, common in automobiles, contain a somewhat concentrated form of sulfuric acid; they are also made of plastic, so assuming they continue to be available, I doubt that such batteries will use this new plastic.
- cr0sh 8y agoI'm kinda curious if this "new" plastic is going to be flexible enough in the number of applications to replace most common plastics in common applications, or if it's going to have the same issues (ie, needing fillers or other things to make it work for certain applications). What is it's heat resistance? How well does it work in extreme cold? How flexible is it? Impact resistance? Can it be made clear? Maybe any fillers, etc can also easily separate out? If it can replace most uses of PP/PE/ABS/PVC - it would be huge on the consumer market (also, providing it doesn't have a similar BPA-like issue).