Mylar vs Teflon


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blarby
December 8, 2013, 01:42 AM
Playing around with some new load recipes in 12 gauge ( while waiting on some pressure testing results to come back) and some of them call for teflon wraps.

The ones specified are .010 teflon wraps.

My question is, would .010 mylar wraps work the same ?

There is a HUGE difference in price.... I mean, I know they are paying to use the teflon name, but comeon.....

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Andrew Leigh
December 8, 2013, 03:41 AM
Whether is makes any difference?

We use both materials in high voltage electrical insulating systems so all I can tell you is about the properties.

Mylar loses mechanical integrity at about 150 dec and will melt at circa 260 deg C.

Teflon will melt at about 330 dec C.

Teflon has a much lower coefficient of fiction.

FROGO207
December 8, 2013, 07:53 AM
^^That there is the deal. Teflon is a much more robust material when used with friction and high temperatures. It is extremely slippery when pushed fast against another surface. Somebody has already done the hard work of making a safe load with a shot shell for you. Make use of their effort. As for the difference if you could sub the more inexpensive stuff they would tell you or not even bother to give the other recipie IMHO.

DoubleMag
December 8, 2013, 08:13 AM
I'm presuming you're using this as a inside the shot cup wrap, to surround the pellets as an added layer against pellet penetration of the cup. Usually for larger shot sizes and steelshot.Yes mylar will be just fine. Also would suggest over the shot card, I cut my own using tyvek.

blarby
December 9, 2013, 12:12 AM
I'm presuming you're using this as a inside the shot cup wrap

Nope. They'd be a buffer all on their own against lead shot, on top of a gas seal. The OS card is a great idea- and those Tyvek ones look just the bees knees.

My question is, would .010 mylar wraps work the same ?

well

more inexpensive stuff they would tell you or not even bother to give the other recipie IMHO.

If it was me selling it to you, I'd tell you the same, right or wrong. Thats not an accurate answer, its a useful and prudent(for your bank account) place for you to stop the discussion. It's interesting that in this case, BPI doesn't address it- they tell you to buy a wad and mylar, or just teflon- both of which magically comes out to right around the same price per shot- I'll be danged. They manage to dance around the question magically- by not bringing it up.

They both would be accomplishing the same purpose. They have the same thickness, for that purpose.

If teflon reduces the pressure from 11,500 to 8500- great. If it reduces it from 9500 to 8500, and mylar reduces it from 9500 to 9000- thats just fine for me. Consequently, if mylar protects the barrel, but raises the pressure from 9000 to 10,500- I'm fine with that too.

Essentially, I'm looking for a technical answer, not the regurgitated "yu'll petcher eye out" answer. Been down that road on so many subjects over the past year that i'm looking for actual useful data- or, barring that, firsthand experience,not internet myths...we've ( those here, not just me ) busted enough of those myths this year already.

Its not that I don't hear what you are saying, its just not an actual useful answer, and may or may not be true. I know, I know- you can't reload steel cases either. Plastic cased ammo will never work. We'll never have an airgun section on THR. Ad Nauseum


Mylar loses mechanical integrity at about 150 dec and will melt at circa 260 deg C.

Teflon will melt at about 330 dec C.

high temperatures

If im reading this right- and correct me if i'm wrong, but we're talking a difference in operating temps of 70 degrees celsius - of which both materials are being exposed to somewhere in the neighborhood of 1760 degrees celsius- and no one puts their eye out either way, using either material ?

Thats a agood answer in terms of eithers' ability to protect your barrel- they would both perform sufficiently in terms of abrasion. In the temperature department, if exposed to bare burning gases, they would both melt. Im deducing from that science, as to the reason either one uses either a wad, or a gas seal, or a stack of fiber over the powder and not just this .010 piece of material.

So, onto the friction portion- thank you for your assistance !

And most importantly, does the friction of mylar on a barrel melt the mylar ? I hope not, as all that mylar sticking out the shotcup over the top thats in contact with your bore would get mighty gooey even being used appropriately as mylar is shown to be.

Andrew Leigh
December 10, 2013, 02:41 AM
Blarby,

I really don't know enough about it other than in the applications that I have used the material. But here are a couple of considered thoughts;

Often there are extremely good reasons for the materials chosen ...... some however do include "marketing hype".

Melting is a function of time and temperature and the thermal mass of the material so although the gasses may be at 1760 deg C the materials are exposed to this for the briefest of time. I can only relate to rifles but typically 1.247ms for my .375. So it could be that the material simply is not exposed for long enough to melt? Do the monowads melt, I have never examined one properly but don't recall having seen signs of melting?

Take a Dacron filler for light rifle loads. Dacron = Mylar = PET = PETP = Polyethylene Perephthalate = Polyester Film as we call it colloqially. Dacron and Mylar are /were both DuPont tradenames for the same product. The Dacron is a fleece which has minimal thermal mass, this gets vapourised with no apparent ill effects to the barrel.

I would doubt if the barrel friction would cause melting. What could happen is that Polyester film has a high shrinkage rate so it could be that if wrapped around the wad that it shrinks and binds the shot tightly affecting dispersion, the Teflon would not shrink. Typically our test have shown that at 130 deg C that Polyester Film shrinks by about 6%. While Teflon to the best of my recollection was about 4%

I would think the the coefficient of friction would be the big advantage in that you would ensure that the shot has the least friction and therefor the greatest throw.

Finally Teflon has excellent chemical withstand properties whilst Mylat is considered to be poor. So the Teflon will cope with the gasses more effectively.

Cheers

blarby
December 11, 2013, 12:02 PM
I wouldn't say that the monowads melt... they do get some heat warp and barrel scrub for certain.

FROGO207
December 11, 2013, 12:18 PM
If you want to try Teflon go to a plumbing supply house and get the wide roll of Teflon plumbers tape. There are several widths available. This will be a really inexpensive way to get it. Unroll and cut off a bit and wrap a couple turns around the wad. A 1/2 inch wide roll yards long only costs a couple bucks at the local hardware store.;) Hows that for saving a buck.:)

blarby
December 12, 2013, 01:09 AM
Its not the $14.00 for 50 to test that bothers me. Its the many thousands of them down the road that do.

wrap a couple turns around the wad.

Unfortunately

They'd be a buffer all on their own against lead shot, on top of a gas seal.

I suppose if you wanted to without buying 50 sheets to try, that plumbers tape wouldn't be a bad try.

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