Recycling and Casting Styrofoam with Solvents

Styrofoam is an ever-present waste material in modern society, being used to package everything from food to futons. It’s also not the easiest thing to deal with as a waste stream, either. With this in mind, [killbox] decided to have a go at recycling some styrofoam and putting it to better use.

The process starts by combining the EPS styrofoam with a solvent called D-limonene. This was specifically chosen due to its low toxicity and ease of use. The solvent liquifies the solid foam and the air bubbles are then allowed to make their way out of the solution. If it’s desired to create a coloured end product, it’s noted that this can be achieved by using other plastic items to provide colour at this stage, such as a red Solo cup.

It’s a slow process thanks to the choice of solvent, but it makes the process much more palatable to carry out in the average home lab setup. It’s possible to then perform casting operations or further work with the recovered material, which could have some interesting applications. It’s not the first plastics recycling project we’ve seen, either – check out this full setup.

[Thanks to Adric for the tip!]

26 thoughts on “Recycling and Casting Styrofoam with Solvents

  1. I wonder whether simply burning styrene to CO2 and water would be the ‘greenest’ direction. Evaporated organic solvents — limonene, toluene, acetone, etc. — are very ‘good’ greenhouse gases, better than CO2.

    1. Anything organic in the atmosphere will be broken down by UV…eventually…they have little to add to the greenhouse effect (tip – look at how much plain old water vapor does).
      They are first and foremost toxic in one way or another to us, THAT is why one should try to minimalize their use.

      And as for burning – you need very high temperatures and excess air (hard to DIY) for polystyrene, otherwise you’d be creating all kinds of organics and soot in the exhaust, waaaay worse then just leaving it in the landfill.

  2. I honestly never considered melting EPS for this. Sounds like a handy process for some projects.

    I’m not familiar with D-limonene. Is there anything special about it as an EPS solvent, as opposed to acetone?

    1. it’s a lot less nasty of a solvent (derived from citrus fruit oils and non-toxic), and doesn’t get trapped in the EPS goo causing bubbles, so the end result is a lot clearer.

      it does take a lot, lot longer to evaporate though, so I can imagine the EPS goo being gooey for quite a long time (days? weeks for larger molds?) when limonene is used…

    2. Well first off, D-limonene smells much better, (and therefore will have a much greater D-limonene is listed in the Code of Federal Regulations as generally recognized as safe (GRAS) for a flavoring agent and can be found in common food items such as fruit juices, soft drinks, baked goods, ice cream… acetone is not, and even then the end result of PS + Acetone is much less end user workable. Limonene is also a non petroleum based organic solvent quite popular for cleaning commercial kitchens and the like.

      1. yes it does liquify into it, just as it does with acetone and toluene and mek, the lacquer thinners were interesting seeing as how they did just melt it down, and you wund u with a lump of not very sticky clay like material. but found that that combo also turns white and bubbles up as it dries. and smells like lacquer thinner.

        1. well im not sure but from my reading i believe what we are working with is atactic polystyrene, which is amorphous like glass and does not really have a regular crystalline structure. so it not crystallizing is not a good measure.

  3. I remember eighties(really scary and frugal here) when ersatz styrofam lacquer(instead pricy nitro one), glue(used to this day by modelers) and putty(mixed with a “saw” dust) was everyday thing…

  4. Why wouldn’t it be more effective to just melt the EPS? Wouldn’t the PS liquify and out gas without adding any additional solvent to the mix. Seems like the PS you would end up with would be a better product without the excess solvent.

    1. not really, its so insulative that you can bake eps for quite a while and the outside may glassify, but the inside stays raw for hours. and requires higher heat bringing it a lot closer to its ignition point. there are big industrial “recyclers” that heat and compact it into solid bricks, those bricks can then be ground up and melted and re-extruded. but much harder to do all that for home use. the addition of the limonene allows the stuff to liquify down to under 200F

      1. these comments are the real MVP’s here. I wonder what kind of scale you can use this method on? would it be effective to keep a tank of mealworms around to eat my styrofoam packaging remnants?

    1. So far ive mostly worked with mostly clean EPS, but starting at the local maker faire a week or so ago, i started a vat of mixed, stuff, take out containers, peanuts, scraps of dirty dusty foam, and most of the crud just settles to the bottom, and if you mostly ladel out the goop and avoid the bottom i suspect it wont be any problem, and trapped under lemon oil its not going to stink much. (i think) its also going to be on the back porch..

  5. Dissolve it in a solvent. Pour into molds then put under vacuum to extract the solvent. Ideally you’ll have a method of recovering the solvent, and of course your vacuum system won’t have anything in it the solvent will attack.

    Or get some gasoline and dissolve enough EPS to make napalm.

    1. gasolene makes for super yellow stinky foamy crud. vacuum does not really do what you think with medium and a solvent, yes it could be closed loop extracted, but probably not cast although at a perfect solvent to plastic ratio it coudl then be extruded into molds or filament or whatnot. but whatever you try to mould in the low pressure is just going to foam up and distort until the solvent is very low, and then you wind up with a wrinkly raisin like version. usually still with bubbles. possibly heating and pulling a vaccuum you might be able to get it thin enough to degas/and evaporate, but my crude experiments with preheating with a hot air gun didn’t really work/help

  6. I am interested in making EPS into a cheap, quick resin sealer & cardboard & paper stiffener. As an alternative building material to foam/foamboard for R/C airplanes.
    The idea is to extend the working life of the paper fibre, to approximate heavy balsa. Retains the easy workability of paper & cardboard–similar to card model builds, yet more robust & durable, with properties like building with wood.
    It won’t be as light as foam building, but should avoid the compressibility, UV, heat & paint/solvent sensitivity of foam.

    I’ve been talking to kids in some poor countries who cannot afford/obtain either balsa, quality foam or much in the way of hobby supplies. Yet they are eager to fly R/C planes and spend what they can get upon electronics, motors, servos, rec’vers and batteries. Cardboard is what all of them start with and they’re really quite good/thorough builders–they merely need to extend their durability & stiffness.

    I’ve already had great success thinning Gorilla Glue, ‘Great stuff’ expanding foam & polyurethane adhesives with Xylene…for this very purpose; however, it seems Xylene is banned in California and other places as a ‘hazard’. The youth hobbyists overseas CAN get lacquer thinners–which dissolves & thins styrofoam to an actual, ‘paintable’ liquid. Far BETTER than mere acetone & it goopy, gloppy nature.

  7. I have been devoting a lot of time to this lately. I use acetone.
    While acetone may not be as safe as limonene, it is a relatively safe substance to use with eye protection and ventilation, and not environmentally damaging. As with chopping onions, avoid eye contact, don’t inhale it, and wash your hands.
    The biggest success I’ve had is is mixing the polystyrene gel with baking soda, to to produce a putty that hardens. Also, this can be cast onto flexible materials such as other plastics, with the effect being that it sticks to the other material when still a gel, but then peels off cleanly once it solidifies.
    More on my process here:
    http://www.artclix.com/plastic/plasticprocess.html

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