PVC -- It's Great for Inventions

PVC, polyvinyl chloride, is a thermoplastic. It softens with heat and rigidifies when it cools again. While soft, it can be bent and even stretched into molds. Cold, it can be sawed, filed, drilled, scraped, or whittled with a knife.

PVC material can be found at most hardware stores in the form of plumbing pipe. I find it to be inexpensive, especially when I consider all the things that can be done with it -- musical instruments, repairs, tools and toys to name a few.

It is resistant to sunlight damage, has a degree of flexibility, is fairly strong, and is electrically non-conductive.

This is a very valuable material for use in inventions; one that very few people seem to be have experience with.

The picture below shows some of the shapes it is possible to make with PVC.

Step 1 Safety while heating PVC

We love plastics for what they do for us, but plastic manufacture and decay tend to pollute the environment and negatively affect our health.

Vinyl Chloride, one of the components of PVC, is carcinogenic. When it is locked up in the polymer, however, it is much safer to be around. In my years of experience working with PVC, I have not noticed any adverse effects on my health from being around it.

Always work in areas with good ventilation. If you do get caught in a cloud of smoke, hold your breath and move to clean air.

When heating PVC with a gas stove or propane torch, try not to let it burn. Smoke from burning PVC is bad. With experience one burns it less and less. Don't panic the first time you do burn some. It scorches, but doesn't immediately burst into flame. Move the material away from the flame and try again. Don't breathe the smoke. Smoke avoidance comes naturally for most people.

While heating PVC over a gas flame, keep the plastic an appropriate distance from the flame to avoid scorching the surface before the inside can warm up. It takes time for heat to travel to the center of the material being heated.

Keep the plastic moving, and keep an eye on the state of the plastic. When heated, the PVC material is flexible, like leather. Beyond this stage, you risk scorching it.

A word from James, the plastic engineer -- "Just a word of warning, PVC can handle some high heats but if it catches fire, you wont be able to put it out, it does not need oxygen to burn so don't do this inside".

I do work inside, but my house is made of cement and has good ventilation. MAKE SURE THAT YOU HAVE GOOD VENTILATION. PLAY WITH FIRE -- CAREFULLY.

Comments

[cart562]

I think it was Phil B's instructables i was looking through and one of them consisted of him putting small pieces of pipe in a pyrex cup with water in it and putting in a microwave. It was great for making small, flat pieces and I was just wondering if you have tried using a microwave before. Btw, apparently the newer Pyrex glass may explode from cooling too fast so either experiment with an old one or be cautious when removing it from the microwave for those of you who wish to try it.

[cart562]

So I knew PVC could be used for a lot of things but this is amazing. I might have to start by making some tool handles. I will never ever throw away PVC again.

[Thinkenstein]

High five! Another convert!

[justjimAZ]

I have had god success using a heat gun rather than flame. I find it is easier and less likely to burn the PVC too.

[Thinkenstein]

I'm sure that a heat gun would work just fine for many projects. I think that propane torches are more common tools for people to own and use, however. The more experience one gets with the torch, the less likely things are to burn. Some scorching does happen sometimes, but I have never had work catch fire.

[lilygist]

How'd you get that flanged end on the knife holder?

[Thinkenstein]

The part of the handle that stretches over the knife blade was just heated to soften it, pressed over the end of the blade, and pinched with pliers to grab tightly. Heat forming is one of the special tricks that PVC can do.

[lilyology]

Oh I should have been more specific, I meant the thing you called a knife holder, the cup with the flanged end, not the knife handle. Did you press it against something? Can the PVC stretch, or will it just tear?

[Thinkenstein]

Oh, I see what you are talking about. It is a piece of 1 1/4 inch PVC, I think. The bottom was closed by cutting tabs and heat folding them to the center, still allowing water drainage. The flared top edge was heated up and pressed over a rounded something to stretch it. Yes, the PVC can stretch, which lets you even mold complex curves into it. Stretch it too much and it will tear.

In the opening photo with the black background, see the domed shapes above the knife to see the kind of stretch you can get from it. You can make male and female molds out of wood, or other materials. Heat up some PVC and squish it between the mold halves to stretch the material to the shape you want.

[lilyology]

That's great, I'm going to try to make a curved horn shape out of a 3" tube. I was originally going to either vacuform or cnc fabricate it, but both are complex and expensive processes for a one-shot thing.

[Thinkenstein]

When you say "curved horn shape", I suspect you are biting off a lot to chew for a first PVC heat forming project. When I bend pipe, I usually fill it with sand to keep the center hole open. Trying to maintain a conical taper at the same time would be difficult. For me, next to impossible, given my basic workshop. That said, go for it! That's one way to learn something, if only to not try it the same way again.

What is the curved horn for? A musical instrument? If so, you can get useful straight conical horns by using x-ray film. (Free for the asking sometimes at hospitals.) Once you clean the image off with a metal scouring pad and water, and let it dry -- silicone rubber sticks it together very well.

[lilyology]

I have access to a hossfeld bender, so I'm going to give that a try when I get the chance. For the cone I'm carving out the shape first with a lathe. Not the most instructablesish way to go, but it's a nice luxury. :)

[Thinkenstein]

I would consider sculpting the curved horn in clay and then putting a layer of fiberglass, or something over the clay to make the horn. Then, just remove the clay.

[lilyology]

That's a good idea, but it's a bit big. I could use chicken wire and plaster cloth and lay it over with plasteline and then the fiberglass, but that's a hell of a workflow and I want a fairly controlled curve on a budget. The horn is for a sculpture, part of it is based on a megaphone. I'm epoxying this bent pipe to a cheap storebought horn, since I don't think I could make the shape. And I'm a little excited to try working with PVC, it's so cheap(!), stable and durable, and seems pliable enough though I've yet to have a great result. I was hoping that sand alone would work to smooth out some of the bends, but the plastic expands and sand collapses. I imagine it's better than nothing. Definitely need a grooved rig to get a smooth curve, unless you've got another clever suggestion :)

[jdougherty2]

I've never done anything with PVC, but I'd think that it might be a bit easier to fabricate your horn in stages. I.e - heat the PVC and bend it to the curve you want. Then cut it down and heat the PVC again, joining the edges to form your cone. Might be easier, but as I said, I've never done this kind of stuff before. :)

[Thinkenstein]

The problem is that PVC has a sort of memory. If you heat up straight pipe to give it a curve and let it cool in that curve, and then heat it up again, it tends to straighten out again as it was originally. Combining two separate steps in one is tricky.

[jdougherty2]

Could you use a jig to bend the curve and then keep it in the jig when you cut it down and make the cone?

[Thinkenstein]

Sounds tricky to me. I wouldn't bet on success, but give it a try. You might learn something new.

[Thinkenstein]

No more ideas offhand. Hope you find a good solution.

[Vinsu]

Truly inspiring. Now I have some use for all those tools I have with no proper handle/no handle at all. Thank you!

[finton]

Excellent stuff Thinkenstein! I recently discovered the joys of PVC moulding myself and seeing your innovative ideas has fuelled my enthusiasm. I particularly like the high-reach pruners.

[Thinkenstein]

Thanks. Glad you like it. It does seem like a material everybody should know how to work with so they can invent solutions to their own problems.

[n0ukf]

Could we get more info and photos on the boat? How long are the pipes? What is its carrying capacity? Are you planning to do an i'ble on it?

[Thinkenstein]

The boat is long gone.  It must have been about 25 years ago.  Pipes a full 10 ft., if I recall correctly.  That's the standard length they come in.  It carried me OK.  I didn't test it for more.  

It was fairly heavy, in part because of the wood.  Not very easy to row.  About the best thing about it was that it only needed a few inches of water. 

A fine experiment, but not worth repeating. 

[n0ukf]

Did the (essentially) grooved bottom (between pipes) tend to act like a keel to help stay straight? What was the hard part of rowing? I've been half thinking of trying this but hesitating because of the $10 cost of each 4"x10' S&D pipe available locally.

[Thinkenstein]

It was not real easy to turn, because it is more like a raft than a boat.  So, the grooved bottom may help one stay straight, or it may hinder one from turning -- depending on how you care to look at it. 

This was a fun experiment, well worth doing, but maybe not worth repeating. 

It was OK to play around with in flat, quiet water, but waves and wind made it hard to make any progress.  It would probably be better to just buy a kayak. 

[n0ukf]

Looking more into this, if I make one, I'd use nine 4" S&D instead of the six 6" (maybe SCH40?) for the main raft and pontoons. Also, in Minnesota, unpowered boats 9' or less don't need to be registered. Over 9' or powered do. So I'd be cutting a foot off each 10' pipe. I'd just have to gather up enough money for the pipe (SCH40 is cheaper 100+ miles away than S&D is locally).

[Thinkenstein]

I'm not suggesting you continue with the project, but if you do these are some further thoughts.

I heat formed the front of the pipes like boat prows to cut the water better. I sealed them with epoxy. Then, the pipes were stuffed with Styrofoam as insurance if any leaked and filled with water. The back ends were then plugged with heat-formed PVC plugs I made and sealed with epoxy. PVC cement sticks pipe together well only if there is a good socket joint. Butt joints are weak, because the cement doesn't stick that well. I felt that epoxy stuck better, and filled gaps.

I made other boat designs, including one kind of like a log-shaped boat cluster of pipes that you sat on like a horse. Nice idea, but didn't work all that well. The flat raft configuration worked better. Any pipes that are out of the water are not supporting weight, just adding to it. A raft is a raft, not really a boat, and is not as maneuverable as a boat.

I did another pontoon boat idea that came apart in fairly mild sea conditions. The kind-hearted, and who knows maybe drunk, boat captain who came to rescue me could have chopped off my feet with his propeller if he came any closer -- another risk of boating.

This row raft with a seat idea was good for very shallow and calm water, but in other situations it was not very good.

[SSmithers]

You have just opened up a whole new world for me. I don't have the proper tools to work metal, and sometimes wood just doesn't work. this also appeals to the inner pyromaniac in me!

[Thinkenstein]

I'm glad you are learning what a great material it is. Start asking around construction sites for scrap pipe. It's an especially good way to get thick-walled and large-diameter pipe free.

[gemtree]

Oh, great idea. I definitely will stop and ask now.

[blowbyblown]

 can pvc be melted down and poured into a mold though?

[fishdirt]

Yeah but it's a high melt. IOW you need a steel die mold. I've been hunting alternatives but can't find any. 350 F is the melt point. You do it in a double boiler pot or with a heat gun until it becomes clear. Another alternative is to buy hot melt vinyl (Vinyl is PVC and vice versa). Vinyl fumes are highly toxic. A safer way, if you have the cash, is smooth on polyurethane resins. It's a soft, rubbery type plastic as well and not as fragile as the acrylic resins.

[Thinkenstein]

There are techniques for casting PVC in molds, or we wouldn't have PVC faucets, etc.  Probably in a home workshop one would not be successful, for lack of special equipment.   Perhaps it needs high pressure and absence of oxygen?

I talked with someone at a PVC factory once about getting second quality pipe cheap.   He said that any defective product just went back into the process again and was extruded anew.  

Anyway, I wouldn't attempt trying casting like that.  You might set it all on fire by accident. 

[blowbyblown]

 well i live on a farm, so i've got plenty of room to not to burn anything down

[Thinkenstein]

I was thinking more about the plastic burning.  Someone wrote that once it catches fire it can continue burning without oxygen, and would be hard to put out.  I've never had that experience, but it pays to be cautious.  Burning PVC makes some nasty fumes. 

[mettaurlover]

Plastic doesn't continue burning without oxygen in my experience. The only thing that I've had do that to me was thermite and that's because it's supposed to do so.

[Thinkenstein]

I tend to agree with you. It doesn't seem like anything would burn without oxygen. I thought that perhaps chlorine in the PVC might be the oxidizer, to explain the supposed burning. The thermite brings its own oxygen to burn.

[mettaurlover]

Yeah, though oxidization, by definition, requires oxygen to occur.

[Thinkenstein]

Maybe. Quite likely. I vaguely recall that in a chemical reaction it has something to do with which one provides the free electrons as to which one is considered to be the oxidizer. That is something like a 45 year old vague recollection from high school chemistry. I am probably wrong.