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
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.
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
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!