Modern plastic is not something you will be able to make on your own. Some plastic are made under pressures of 45,000 lbs or more. But plastic even though you will not be making it yourself can still be considered here because it is going to stick around for a long long time. Hundreds of years after the last bomb falls you will still be able to find plastic as it does not rot like wood.
Identifying the different types of Plastics and what each is useful for will be useful information after the SHTF! Luckily identification is super easy because they plastic often has the type of plastic it is stamped right on the end use product it was used for.
Here is what you are looking for. The triangle ring of arrows surrounding a number. This is how todays plastic products are marked so they can be easily identified. The number inside the triangle lets you know which type of plastic you have.
If the number in the triangle is a 1, then you have PET plastics or PETE (Polyethylene terephthalate). End uses include polyester fibers, thermoformed sheet, strapping, soft drink bottles, tote bags, furniture, carpet, paneling and sometimes new containers.
If the number in the triangle is a 2, then you have HDPE (High-density polyethylene). Bottles, grocery bags, milk jugs, recycling bins, agricultural pipe, base cups, car stops, playground equipment, and plastic lumber.
If the number is 3, then you have a PVC product (Polyvinyl chloride). Pipe, fencing, shower curtains, lawn chairs, non-food bottles and children's toys.
If the number is 4, then you have LDPE (Low-density polyethylene). Plastic bags, 6 pack rings, various containers, dispensing bottles, wash bottles, tubing.
If the number is 5, then you have PP (Polypropylene). End uses include Auto parts, industrial fibers, food containers, and dishware.
If the number is 6, then you have PS (Polystyrene). End uses include desk accessories, cafeteria trays, plastic utensils, toys, video cassettes and cases, clamshell containers, packaging peanuts, and insulation board and other expanded polystyrene products such as Styrofoam cups.
If the number is a 7, then you have what is known in the recycling world as OTHER. Just something not listed above. Some end use products that might fall under the other category would be a few bottles, maybe some plastic lumber, Headlight lenses, and safety shields/glasses.
A word of caution. Just because a plastic says it is HDPE or LDPE etc doesn't mean it will be the same as all other products in this category. Additives and melting temperatures for various LDPE plastics can actually range from liquid at room temperature to stuff that has a melting point of over 700 degrees. Some have additives, some are homopolymers where as others can be upwards of 30% of some other type of comonomer such as vinyl acetate.
When possible you should try to use the same source of plastic for each product you are making.
Which Plastic is best!
Well that depends on exactly what you want to make with it. But I like HDPE 2
and LDPE 4
the most. If you can find enough of it I would prefer to work with nothing else other than 117.85 LDPE from ExxonMobil or other such products because it contains an additive in the plastic that prevents the plastic from sticking to metal. This allows for metal molds without any barrier between the melting plastic and the metal. Just let it cool and you can fairly easily remove the now solid plastic from the mold.
PETE 1 I have never worked with because it requires such a high melting temp. LDPE and HDPE usually melts around 250 degrees. Pete 1 usually melts at 500+ degrees which I don't care to mess with but of course if you are making something that will need a high heat tolerance then PETE 1 is what you want.
Number 5 has a melting point that is a bit higher than 2 or 4. Usually about 100 degree F higher but not always. But it has many of the same properties as 2 and 4 and is a good choice.
So what can I make with this stuff!
This is a very short list as the uses are only limited by your imagination. Clothes, lumber, cutting board for the kitchen, rope, string, tools, plywood substitute that is better than plywood, shield, roofing material, utensils etc etc.
How do I make this stuff
Method 1. Make an appropriate sized mold (4 sides and a bottom) out of wood or anything that will not melt or catch fire easily. Screwed together is better than nailed. This is so after the plastic solidifies you can disassemble the mold which will make separation a lot easier.
Now you need to heat the plastic up either in the mold or in a pot that will be used solely for this purpose. The plastic can be put in the mold and melted or melted in a pot and then put into the mold. Obviously you don't want to put a wooden mold directly in a fire as it would burn. Each method has its advantages. Melting in a metal pot is faster as the wood insulates the plastic. It just all depends on the application. Don't have an oven, then melting in a pot is the best choice.
So at this point the plastic has melted and is in your probably wooden mold. Now let it cool. No need to hasten the process just let it cool on its own. Remove from the mold and wallah you have your product which may or may not need further work.
Method 2. Fill a metal pipe with plastic and cap both ends. One end will just be a solid cap and the other will have a hole that you drilled. Melt the plastic and then force the plastic out at a steady rate through the hole and you have a solid plastic rope like material.
Method 3. Spread out a thin layer of plastic over something such as a hood from a car. Heat the hood with fire and the plastic will melt to form a thin layer of molten plastic. Thickness is going to be the thickness that you made it initially. Do not expect the plastic to flow like water or to even itself out like water. Let it cool and if it was done thin enough then you should have a pliable plastic sheet that can be made into a bunch of things including clothes or a poncho, shower curtain etc.