Instructables

How to make super cheap strong castable SULPHO-PLASTIC

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Ok, I have recently done some experimenting with mixing LDPE and sulfur, and to my suprise, the result is a very tough, stiff material that is much much stronger than the original LDPE. This stuff is amazing, easy, and extremely cheap to make. I have updated the instructable to include the steps for making this LDPE sulfur plastic.

If you use no LDPE, the sulfur comes out brittle and crumbly, so it is useless alone. However, you can mix it with aggregates such as sand and gravel to make a very stiff and fast drying cement.

 
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Step 1: Materials

List of materials

1. Sulfur- can be powder or pellets or anything that is plain elemental sulfur. You can get this at a farm supply store. I got 50lbs for $30. It can have impurities up to maybe 20%. More impurities equal less strength. If you don't want large quanities, buy some from here>http://doitbest.com/Main.aspx?PageID=64&SKU=722367&utm_source=Froogle&utm_medium=FREECSE&utm_term=722367&utm_content=6790&utm_campaign=DATAFEED


2. Aluminum foil- optional- I got this at Cosco for $15 for two rolls. This comes out to be 5 pounds of aluminum. If you don't want large quanities, get a roll from the 99 cents store. This is used as an aggregate.

Edit: I found Aluminum foil to be a great aggregate, but you can use other things like rocks or sand to make it stronger. Also, try painting the sulfur directly onto some fiberglass and layer it like a surfboard. I find that makes for a very strong sheet of plastic. Just make sure you get the sulfur down into the cracks because it dries quick.

3. LDPE - get this either from recycled plastic, such as milk bottle caps and other flexible lids, or online here>> http://www.birchplastics.com/ 
or here>> http://www.amazon.com/LDPE-Density-Polyethylene-Length-White/dp/B0013HL0OY/ref=sr_1_7?ie=UTF8&s=industrial&qid=1267304312&sr=1-7 
this comes out to about 7 cents per cubic inch, or 2 dollars per pound.

Total costs-
75% LDPE + 25% sulfur- about 1.70 per pound
25% sulfur + 75% aggreagate (sand and rocks)- 0.15 per pound

**all percentages by weight***
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shizumadrive6 months ago

For the teeth molds find an orthodontist and he'll tell you the alginate stuff he uses to make mouth molds/impressions. My dad was one and I don't know what the mold stuff was made out of but it was safe to be in your mouth. They filled the mold with plaster which isnt what you wanted but the mold making itself there is some good stuff out there. Have no idea how much it costs I got it for free.

me351 year ago
Great ideas. I was looking for someone to create a cheap durable and self leveling compound for my wood floor. I don't like the concrete idea but if someone could come up with a self-leveling type of plastic that would be durable and self adhering to plywood i think they would be on the market for big money!
alz193 years ago
nice instructions I am inspired to try them.Just one question.Any idea how to make the sulpho plastic of a particular color like dark brown,red etc
donkeyot3 years ago
http://www.make-stuff.com/formulas/sulphpl.html is quite interesting and if you check out the formulas and other tabs one show where you can buy this type of stuff from and how to mould it. Sulphur has many unusual properties its used as a plasticizer to rubberise plastics and increase the wear and tear properties of tyre rubber. Quenching makes it brittle and hard, slow cooling makes it highly rubber ( like those small rubber balls that bounce forever all over the place). Graphite has a ring structure that can form very strong bonds, glycerine too, (dont make nitroglycerine though) and benzene rings like found in toloune again dont add nitrogen or pressure or allow to boil. If you drop some and it exlodes walk gingerly to a bucket of water and pour it in slowly. Benzene rings are very stable and form very strong bonds for plastic, but usually reuire a catylist and appropriate strucural alignement, ie 1-3, dihydrosulthobenzene, would form chains. with an ethylene molecule. 1-3 dihydroxybenzene, something like that anyhow. As i say check out the above website they also tell how to make different plastics out of common ingrediants. Hope this helps
servion4 years ago
Can I melt this in high detail molds?
galaxyman7 (author)  servion4 years ago
Yes you can pour it into high detail molds. The sulfur will fill the fine detail. The hard thing is getting the stuff out of the mold. It sticks to most things. Try car wax, that seems to work well to keep it from sticking.
sethy894 years ago
Hey man that's an AWESOME instructable! It might be just what i was searching for...
but I need to know a few things about the results of the sand, ldpe and grafite(case you or someone have tried):
1. did any piece got brittle over time?
2. wich resists more to tensile strenght and which was the lightest?
3. i've read that this plastic is inflamable... but how fast it burns?(I mean the final plastic not the mixture)
4. can u give me some relation between weight of the mixtures to the volume of the resulting plastics?
5. someone said the plastic reverted to powdered sulfur... it happened to any of your pieces?(i believe it happened cause he hasn't used any addictive, but maybe i'm wrong)
6. what kind of sand you used? crystaline, red...?
Thanks.
galaxyman7 (author)  sethy894 years ago
1. No, the plastic does not get brittle over time, I think the sulfur actually cross links with the polymers like Qcks said.
2. The mix between just LDPE and sulfur will give the lightest material. I have not tried mixing it with sand, and really don't think it will do anything.
3. the plastic is very slow burning, but once it is started, it will keep going. It is pretty hard to light it though, it won't just catch fire easily.
4. You can't really control the amount of sulfur per plastic, you just melt some sulfur and mush the glob around in it, and it will absorb the right amount.
5. It has never reverted to powder, I am pretty sure the sulfur is in its lowest energy state in the plastic. I have pieces that are a year old and have not changed.
6. I have not tried sand yet, you will have to experiment. Also try fiberglass layers. You can get fiberglass cloth at the hardware store, they sell it for repairing cars.
Thanks for the help! I'll buy the material and send you the pics when i finish it
m0tkid4 years ago
 Hey dude this is really awesome. I have a few questions though (and I apologise if they've already been answered, but i looked - honest!)

1) can it be sanded/drilled/cut
2) if you do the chemisty, does it work out to be an actual polymer?
3)Either way, what is the chemical composition of the sulfur matrix that you 'embed' the aluminum in?

Thanks!

Ps. If i make some in the future I will email the materials science lecturer from my uni and see if I can run a tensile/rockwell hardness test on it. =)
Qcks m0tkid4 years ago

There's a few things that could be happening considering Liquid Sulfur reacts with aluminum, and it might react with graphite, depending on conditions and exact structure, however... i think this is just a sulfur reaction.

en.wikipedia.org/wiki/Allotropes_of_sulfur

Assuming the information provided by the Wiki is correct, heating up and quenching your liquid sulfur would result in a stronger product.

With regard to adding graphite, it's possible that you get a bit of cross linking occuring between the carbon and sulfur, but that scenario largely depends on the shape of the carbon molecule.

Rather then using aluminum foil or graphite, I think people might get a good result with using finely chopped up plastic shopping bag. Plastic shopping bags are mostly polyethylene, which i believe can cross link with hot sulfur.

m0tkid Qcks4 years ago
Qcks, I was under the impression that the sulfur acted as a matrix and the graphite and/or aluminum was acting as an aggregate - much like blue metal in cement to make concrete.

From what you are saying you believe there is some actual chemical bonding occurring between the sulfur and the additives?

- I agree with you on the polyethylene - being a thermoplastic it should melt down with the sulfur and chemically bond/interact with it.

I am not a chemist/chemistry student though so I am not exactly sure if my thoughts are on the right track... Feel free to set me straight
Qcks m0tkid4 years ago
Sorry bout the speed on the reply... I get distracted easy.

With regards to what's going on in the actual finished product, I'm not 100% certain. I'd need to conduct a number of tests to know for sure, and it's more then a little outside my means.

What I do know for certain though is that Sulfur is fairly reactive and undergoes a number of processes which are pertinent for the average DIYer (since the average DIYer probably doesn't have vacuum chambers and such). It reacts with oxygen, water, and is a favored reagent for this reason. 

In organic chemistry sulfur rings, which is likely one of the forms produced, are used as a crosslinking agent (meaning it can bond two plastic polymer molecules), hence why I suggested using polyethylene.
As for a reaction between graphite, Graphite is very plastic like, which is why I think there maybe an actual reaction that takes plasce there, but, as I said, I'd have to look into it more. The type of graphite used (crushed lubricating graphite) probably changes this.

As for Aluminum, Unless it's an algum or a protected type of aluminum, the sulfur wouldd react with it to form a sulfide. After looking at it a bit more, aluminum sulfide readily reacts with water to give aluminum oxide and Dihydrogen sulfide... so there's not as much worry about distortions resulting from the reaction because aluminum oxide is pretty durable, but a slow release of hydrogen sulfide might be an issue.

Any way... this is just what I know... experiment an see how it works
galaxyman7 (author)  Qcks4 years ago
Wow! I just melted some sulfur and put in some LDPE. I mixed it together as much as possible, then took it out of the sulfur. This stuff is amazing! I can't bend it at all, yet it isn't brittle either. The piece I made is probably only 1/4 inch thick yet there is absolutely no bending! It is almost like metal! You guys should really try it! I will update the instructable.
galaxyman7 (author)  Qcks4 years ago
That is interesting, you said aluminum reacts with sulfur? Do you know the chemical formula for that reaction?
Meanwhile I will try some different types of plastic and see how that goes. I think LDPE would work best because its melting point is below that of sulfur's. I will probably use some scrap milk bottle caps.
Also, recently I have found that increasing the aggregate to around 75% volume seems to be the best. I used sand and gravel and it turned out great.
Only problem is that it cannot be machined with the rocks in it, so it would have to be poured into a mold. I will try a mix with only sand and see how that works.
galaxyman7 (author)  m0tkid4 years ago
-It sands very easily, but cracks when drilled. I'm guessing you could cut it with an angle grinder, but I haven't tried.
-I have no idea what the chemistry is for this. It seems to depend heavily on how long and how hot you heat it. I have had very weak mixes of the stuff and very strong mixes. I think the crumbliness comes from getting the sulfur too hot.
- If you could figure out the chemistry, that would be awesome. I don't even know if graphite does anything.

One more thing- I think the material could be milled with a sharp bit or sanding bit, so you could make a mix of pure sulfur, pour it into a sheet, then mill it out.
fuzvulf4 years ago
 You could probably increase strength using bits of fiberglass pulled from the "itchy" pink style of insulation and mixing it in with your concoction.  I have a set of old books that has something similar to this but without the graphite and using babbit or "white metal" shavings to cast shapes.  fun instructable. 
galaxyman7 (author)  fuzvulf4 years ago
That is very interesting. What is the recipe in the book?

By the way, I have experimented with putting different materials in with the sulfur, and it cools the sulfur down too much for you to be able to mix it in after it is melted. I wouldn't recommend heating up the pink insulation with the sulfur either.
galaxyman7 (author) 4 years ago
This stuff is actually pretty useless except for concrete. I reccomend using recycled HDPE instead of this "plastic". I will take this instructable down.
galaxyman7 (author) 5 years ago
By the way, If anyone has any ideas for increasing the strength more please post them here.
I wonder if aluminum powder would work better than aluminum flakes. I think you can get powdered aluminum from chem supplies online.
Thenwcp Pazzerz4 years ago
http://www.highqualitychems.com/servlet/StoreFront
or unitednuclear.com for small quantities

keep in mind powdered aluminum is pretty dangerous, especially since you will be pouring it near an open flame...the powder tends to explode when it gets into the the air and is exposed to flame.
galaxyman7 (author)  Thenwcp4 years ago
Ya I know. That is why you only grind it in a blender, so that is doesn't actually become powder, but more like granules. Aluminum powder would probably be a bad idea.
galaxyman7 (author)  Pazzerz5 years ago
You might try aluminum powder, but I think flakes actually increase strength more. Kind of like the rocks in concrete. But be my guest, I heard once that someone used aluminum powder instead of graphite powder, so that might be something to look into.
Or how about this: steel wool, about 1/2 to 1" long fibers, in place of the aluminum (unless you can find aluminum wool). Another thought is the aluminum screening for doors and windows for pieces that are flat. I suppose it could be bent into shape to match a mould before pouring.
galaxyman7 (author)  Pazzerz5 years ago
That's a great idea. Fibers would give it a ton more strength and window screen is probably the best bet. Thanks, I will try that out.
does the plastic react to water?
galaxyman7 (author)  123456789pos5 years ago
no it doesn't. By the way I really reccomend fiberglass cloth or something to reinforce it. Plain sulfur and graphite isn't really that strong. Use rocks or aluminum as an aggregate.
galaxyman7 (author)  galaxyman75 years ago
it doesnt soak up water either
Biopyro5 years ago
Excellent. I can't believe I haven't heard of this before!
galaxyman7 (author) 5 years ago
Just posted some pics of new castings I just did. They turned out really well. I am going to upload the video of me making them to youtube.
Interesting, honestly I was gonna call BS, but found this reference.
linky

Questions, is it stable? Does it smell like sulfur? Does it shrink much?
For a short while, sulfur was used in woodworking inlay. It's stable enough to last centuries : )

http://www.popsci.com/diy/article/2005-01/worst-way-inlay
Interesting, I as curious because we did a project in Junior High were we quenched molten sulfur to make plastic sulfur, which over time reverted to powdered sulfur. I guess slow cooling forms a different stable structure.
I was looking in Wikipedia, and a quick cooling of sulfur creates a flexible, helical crystal structure that changes to a more stable one over a short period of time. The PopSci article mentions that the sulfur turns white over time (100 years).
DItto those questions, and also- is it brittle? Is it particularly elastic, or bendable when cold? How fine detail can you cast with it?
galaxyman7 (author)  Tool Using Animal5 years ago
Nice link by the way, I haven't ever seen any evidence of this stuff working, so I tried it myself. This plastic is basically the same thing, except it has more graphite and aluminum mixed in. I will try to post a video of me cooking the stuff, once I get my video camera to work.
galaxyman7 (author)  Tool Using Animal5 years ago
It does smell like sulfur if you put it up to your nose, but it doesn't smell if you don't. It shrinks to about half the volume of the powder, and yes, it is stable. I have a piece of the plastic I have kept around for a month, and it is still the same. Just make sure when you cook it not to heat it up too much. I tried using my toaster oven, and man did it smoke. It gives off SO2 if you heat it too much, so try to just use the barbeque and heat it slowly. When it starts to liquify, keep it at that temperature.
galaxyman7 (author) 5 years ago
Also I noticed that if you don't pour it all at once, but you pour it over itself, it is much less strong because it has layers and air pockets inbetween, so try to get the plastic so that it is very liquid and when you pour, and pour in one spot until the whole mold fills up. Another solution, like I suggested in the "Pour it" part, would be to heat up the mold in an oven before pouring into it.
galaxyman7 (author) 5 years ago
Anyone planning to try it? Just wondering.
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