PVC vs. ABS

Post questions and info about safe and unsafe materials that can be or should not be used to construct a launcher. Also post things about different universal accessories for your cannon (breech loader, muzzle break, etc.)

Postby PCGUY » Fri Apr 28, 2006 7:36 pm

<font color="green">Orignally posted by ryno, however stupid Snitz archived it so I have to repost it.</font>

This should help decide between PVC and ABS. This is taken directly form the Construction Materials page on spudtech.

Below is brief discussion about various things typically used, some not so typically used, and yet some things that you can probably only dream about.

ABS (also see topic #1 on the FAQ page)

-Technical Name: acrylonitrile-butadiene-styrene.
-Trade Name: Marbon, Cycolac, Lustran, Abson.
-Regular Applications: Sewage/Drain systems for most modern buildings within confines of foundation, highway safety devices, toys, potato launcher barrels and combustion chambers.
-This material has long been that standard as far as I have known for constructing potato cannons. Strong and very light. (cellular core)

PROS

-Chemical resistance, so can stand up to the average weekender going crazy experimenting with every different thing that can be found in an aerosol can.

-Light weight, even the weakest of us has no reason to heft and bear these devices.

-Low cost, it can be obtained almost anywhere, in the correct dimensions.

-From what I've seen, when it fails, it spilts down the side, unlike PVC where it turns into shrapnel, so it seems it would be safer.

CONS

-NOT PRESSURE RATED! This material has been proven to be acceptable, but standard pipe is not certified for any pressure service above those found in gravity drain applications, typically not above 10 psi. The term "cellular core" means that millions of tiny air bubbles were whipped into the plastic before it was run through the extruder. The end result is a very light weight material that in effect is nothing more than a piece of hard foam in the shape of a tube.

-Decomposition products are nasty! If you have ever taken a whiff after firing it a few times, you will get a burning in your nose. This caustic gas is not good for you!

Although an acceptable material for construction of these devices, a few cautions should be exercised. Never attempt too large a reduction from chamber to barrel in pipe sizes, and this is dependent on the chamber volume. If this is too high, a container failure is risked. Never attempt to use an oxidizer other than atmospheric air, or rupture could occur. ABS is fine for the construction of combustion spudguns, but I personally tend to stay away from it. All the chemical and heat resistance in the world isn't worth a damn if it's not pressure rated.

PVC (also see topic #1 on the FAQ page)

-Technical Name: polyvinyl chloride
-Trade Name: Pliovic, Saran, Tygon Regular
-Applications: fresh water delivery systems, electrical wire insulations, LPs, potato launcher barrels and combustion chambers.
-Invented at the University of Washington Department of Chemical Engineering, this material has been so instrumental in our everyday lives. Being so inexpensive and versatile, it is used in many fashions not limited to the list above. It has even found widespread use in the potato discharging industry!

PROS

-Inexpensive, the pipe is almost free. Fittings are where the money is dropped, but well worth it

-Multitude of dimensions to chose from. Pretty much any configuration of pipe fitting can be found somewhere in PVC, but get out your checkbook! 6" sch 80 will run you right around $40 for a 10' piece.

-Pressure Rated. What you see is what you get. The rated pressure on the side of the pipe is already conservative, so you don't need to incorporate safety factors, unless you want to. Fittings are always stronger than bulk pipe, as long as the glue joints are made and allowed to cure properly and are Schedule 40.

-CONS

-Limited Chemical Resistance. Aldehydes and ketones are out, as these readily dissolve the polymer, as in a glue joint, just read the label on the can: Acetone, THF, MEK. Some fuels should be totally avoided such as carb cleaner and insect repellant, don't say I didn't warn you!

-More brittle than ABS, but by not using oxygen and just burning fuel and air....should never be a problem.

-Cellular core PVC is common at many hardware/home improvement stores. Make sure you buy SCH 40 pipe with a pressure rating printed on the pipe. If the pipe is not specifically marked with a certain PSI rating, IT IS NOT PRESSURE RATED!!

PVC pipe is the most widely used material to date, it provides many ideal characteristics for use in this field. Just look out for chemical incompatibilities with certain fuels, but most will not present a problem. I can sort of feel a small war going on between the use of ABS vs. PVC, and with my experience would go with PVC if I had to chose between these two things. Reading further may provide more information about what may even be better these days...
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Postby EJS06 » Sun Nov 19, 2006 11:11 pm

What If you can not find pressure rated pvc larger than 2"? Where can I get some?
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Postby spudproof » Sat Nov 25, 2006 9:13 am

IT STANDS A PLACE AT THIS SITE THAT cellular core IS not OK TO BUILD WITH
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Postby Kenny_McCormic » Sat Feb 17, 2007 4:48 pm

ok heres a question is abs better in the cold than pvc can i use abs below freezing?
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Postby security1 » Sat Feb 17, 2007 7:45 pm

Plastic of all types, become brittle in cold weather. The colder it is, the worse it is.IE Dont play with shrapnel.....
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Postby TurboSuper » Sun Feb 18, 2007 12:52 am

If you really plan on shooting in the cold then I would just go with a metal gun.

Better safe then pulling plastic out of your ass with a pair of tweezers.
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Postby Kenny_McCormic » Mon Feb 19, 2007 9:41 pm

good point i wonder if auto exhaust tubing would work well my dads a mechanic so getting the materials wont be hard
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