Coefficients of Friction for rubber and polymers 1

[gibsoni]

Hi,

I am looking for a material to use as a seal. It needs to slide very easily over PVC (machined pipe) and I am having a hard time finding something to do the job.

Is there a resource page that might indicate friction coefficients for various rubbers and polymers (I assume against a standard material such as ground steel, itself, or similar)

Thanks for any suggestions. I have tried a neoprene sponge FYI.

Regards, Iain.

 

[patprimmer]

How uch of it are you looking for

Regards
Pat
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[gibsoni]

Sorry, Should have been more specific.

Having found out what materials have low CF, I would then search around for someone who does or can make this into 12 wide, 3 thick strip and apply an adhesive to it.

Regards, Iain.

 

[patprimmer]

So I guess you want to buy small sheets one at a time rather than have something moulded.

I ask because moulds can be very expensive and not all materials are readily available in sheet or block form.

12 yards wide and 3 foot thick is pretty big although zero length saves on material.

Regards
Pat
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[gibsoni]

I am not sure if you are joking or not...

12mm x 3mm is the units. length? Typically they come in 20m lengths.

 

[patprimmer]

At last. Some info we can begin to work with.

Is that seriously 20 meter length or is it typo for 2.0 metre.

At 20 meter is going to be very difficult to handle and transport unless you roll it up.

I expect you might need to extrude a profile. It will be a very simple die.

Lets pull another tooth.

How many lengths do you need. Are they really 20 metres each.

Data against steel will be next to useless when trying to determine performance against PVC.

There are quite a few variables being glossed over or ignored.

I am sick of pulling teeth. If you really want a useful answer take the time to think through and draft a properly thought out question.

Details like how many pieces per week, environment of use, like wet or dry or lubricated in any other way and temperature might prove useful.

Speed and level of the load is also a critical issue.

How long the friction is applied is also critical.


Regards
Pat
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[cloa]

He did say it was a seal and referred to it as a strip so why anyone would think it would be a plate.

 

[patprimmer]

Who said it was a plate. I still don't really know what it is. Seal and strip descriptions do not tie it down very much.

http://en.wikipedia.org/wiki/Strip

http://en.wikipedia.org/wiki/Seal_(mechanical)

Is it a rope packing type seal to seal the shaft of a pump.

Is it a compression olive type seal to be compressed between two tapers.

Is it a lip type seal similar to those now commonly used as oil seals on automotive crank shafts.

http://www.rtpcompany.com/products/wear/index.htm

Sifting through some of this may help, but as I am trying very hard to indicate, there are a few traps for young players.

Also it really depends on volume to determine if something off the shelf has to do or can be adapted or if something can be custom made.

Regards
Pat
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[tr1ntx]

Iain,

Check with PolyHiSolidur (if they're still around). 15 years ago they were able to provide plastic/elastomer data I couldn't find anywhere else.

I wasn't using it for a seal, but I used UHMW-PE against gray PVC pipe with good results. The load was low and the UHMW was rubbing against the slick as-extruded surface, though, so it probably doesn't tell you much.

You might try a multi-contact point hard seal of UHMW or PTFE if you can't find a soft seal that won't try to stick to the PVC. You might want to check with O-ring manufacturers to see if they have material-to-material friction data for their dynamic seal applications. You would think surely they do. I high durometer fluorosilicone or fluorocarbon might do the trick, if you don't mind paying for it.

Did you solve your clevis pin problem?

 

[gibsoni]

Thanks to you all for your comments.

This is a seal around the internal diameter of something similar to a lid. The part has a machined internal groove to take the seal. This then slides over a turned taper and then along the side of the pipe (as extruded) for a very short distance.


Might have solved the pin problem. I have made a 1045 pin and put it into service to see how it goes.

 

[patprimmer]

You said it needs to be glued at one stage. That excludes any PE.

If you want to mass produce them, UHMWPE can't be injection moulded.

It sounds like bearing properties are not an issue but force required in application is.

Polyurethane can be had in grades for injection moulding or simple two pot mix type casting. It has a moderately high CofF It is commonly used for tap washers. There are a great variety of grades.

We are still trying to guess if you need a material for a one off or the occasional part or mass production. This is really required info as some materials need to be moulded in a mould that costs thousands of $, others can be poured into a simple mould and others can be purchased as blocks or rods. Some can be had for all three, but some only for one. That is why I keep harping on about that point.

Regards
Pat
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[gibsoni]

This product needs to be already available in something similar to the self adhesive foam strips that I purchase at present. My manufacturer has a great range of materials to choose from but no data on friction coefficients.

This is some of there range-

http://www.completerubber.com.au/downloads/tape.pdf

I would love to know which of these might give the best sliding action (min friction) as a start.

Thanks for your help!

 

[tr1ntx]

At a glance, I think I would try the FS560 PE sealant. That's the only one that doesn't say it's foam, so I'm assuming it is a solid PolyEthylene shape (round I guess). I picked the FS560 over the other "FS" listings because I assume the higher number means higher durometer or density. That may not be the case.

The NorSeal V710 is medium-density PVC foam. I don't know if PVC-to-PVC has any strange adhesion, but you may want to try that. I would think that the like materials have a better chance of working, although it seems to me that the foam seals will rip apart, but without knowing more about the motion/forces it will endure, I'm just guessing.

When I made a tapered part from gray PVC pipe years ago, the machined surface was rough and tacky/sticky. I want to point out that we weren't concerned with that OD surface, so we didn't try to get a smooth/slick finish. I mention this because it caught us off guard. We ran the lathe at its lowest speed, but it still tended to gum up. This was thick wall pipe (at least 1", maybe thicker) and we were trying to machine a full taper down to the ID. The very outer potion machined nicely, but the core was soft and sticky.

 

[unclesyd]

Here are two approaches you may want to investigate. Venture Tape has tapes from many materials. If you can use it the best way to go would be with heat shrinkable tubing from Zeus. Zeus has many products made from fluorocarbon materials that would be quite slick.
I would get my ducks in a row and give Zeus and Venture a call.

http://www.venturetape.com/product.php?productid=1329&cat=42

&page=1

http://www.venturetape.com/home.php?cat=7

http://www.zeusinc.com/extrusionservices/products/heatshrinkabletubing/heatshrinkablerollcovers.aspx

 

[dragracer9]

coat your materials with a dry lube. say MoS2 or WS2. They are cheap and wont rub off.