How to Make Super Cheap Strong Castable SULPHO-PLASTIC





Introduction: How to Make Super Cheap Strong Castable SULPHO-PLASTIC

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.

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>

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>> 
or here>> 
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***

Step 2: Instructions

Sulfur + LDPE-

First heat up the sulfur in a pot until it is smooth and all the chunks are gone. Keep it a little hotter than its melting point.

Then once the sulfur is melted, add the ldpe scraps/ rod. They will form a large glob in the sulfur. Do not add ldpe until all the sulfur is gone because you want the heat from the pan to be spread out evenly and not burn the plastic.  You do not need to measure the amount of sulfur or ldpe, because the excess sulfur will be left in the pan.

"Knead" the plastic with a spoon so that the plastic is thouroughly integrated with the sulfur. Fold it over itself many times, and also cut into it letting sulfur flow in.

Once you think you have mixed it well, take the glob out with a spoon and press it into your mold. It should only take a minute or two to dry, then take it out.

Let it sit for a day before using it! The bonds between the sulfur form very slowly, and playing with it will ruin it. After that, you will have a hard, almost metal like peice of plastic!

Sulfur + aggregate

Do pretty much the same thing as the ldpe, except put in rocks and sand instead of ldpe. Use 75% rocks/ sand, and 25% sulfur. The rocks and sand will cool off the sulfur and make it take forever to melt down again, so be patient.

Aluminum granules can also be used in place of rocks and sand. Just use an old blender to chop up the aluminum foil in water, then mix the granules in with the sulfur.

pour it into the mold and let it cure for a day.

Step 3: Experiment

Experiment! Try using ldpe, sulfur, and aggreagate and see how that turns out. Try making it conductive by adding copper. The best thing about it is if you screw up, just remelt it and pour again!

Step 4: Make Some Awesome Stuff!

Make some awesome stuff and email your finished pictures to me at I will post them on this page.  Also if someone could email me some properties of this plastic like tensile strength or shear strength, that would be great. I don't have the equipment for that kind of testing. Also, subscribe!



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    I want to try this to make my own mat tracks for wheeling. How would you recommend doing a large item about 3 feet long? Any way to melt all and poor? Or would doing it little by little be ok or would that nak3 it weak?

    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.


    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!

    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 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

    Can I melt this in high detail molds?

    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.

    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...?

    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