Adhesive wear in two rubbing teflon hoses

[PLukacovic]

Hello, I was hoping someone could lead me to information regarding what I believe is called "homogenous adhesive wear". It's the tendancy for a material rubbing up against a component of the same material to wear and chafe faster than if two different materials were wearing. This is most common in polymers, I believe. In our case, it has to do with teflon hoses.

I learned about this in college, briefly, while working on a friction project. The TA mentioned it in passing, and it hasn't come up again until now, so I don;t even know how accurate this information is. A cursory survey has turned up nothing.

We are looking for alternative solutions, but we would like something for our records.

Any and all information is greatly appreciated.

Thank you so much for your help.

 

[IRstuff]

Rubbing is bad, regardless. There was a thread a while ago about cotton thread cutting through steel guides.

If it rubs, it's just a matter of time before something fails.

TTFN

FAQ731-376

 

[romke]

when two objects from the same material rub against each other, there will be some adhesion forces between them. this may result in temporary bonding with a high wear rate as a consequence. therefore it usually is better to use materials with a different composition if that is possible with respect to the strength requirements.

the phenomenon is not restricted to polymers, but can also seen with metals.

the best way to avoid the problem is to prevent any chafing at all, if that is not possible materials with a different nature or coating one of the two components may help, as will also the use of a suitable lubricant.

you should google for polymer compatibility - you will find a lot of links dealing with contact phenomena between various materials - also the supplier of the hoses might be able to give some useful advice.

 

[mighoser]

I know Saint Gobain Films, Foams and Fabrics Division makes a abrasion wrap for GE Aircraft Engine wiring and hydraulic lines. I believe it is an E-glass fabric coated with PTFE. You could also try spraying some Solid Film Lubricant (MoS2) on the teflon tubes. Assuming it sticks, it might help to eliminate any adhesive wear tendancies.

 

[unclesyd]

The post by mighoser ran a bell among the windmills concerning Teflon hoses. I had someone lookup our specification for Teflon hoses as to what we called out. All our specs. call for any Teflon hose to be wire rapped with SS mesh or Kevlar mesh. Looking back at my notes I also see reference to a polyethylene sleeve wrap. Looking at a few old catalogues all the companies have a least a SS mesh wrap for Teflon hoses. It looks like the mesh covering adds nothing to strength level, that is it's only for chaffing.

You might search on Teflon hose chaffing.

 

[coatingengineer]

Hi.

Friction is much different between thermoplastics, than thermoplastics rubbing on metal. Particularly at elevated temperature. Wear rates will increase measurably. Sorry, I found no reference to temperature in this thread.

But, even at room temperature, as you would expect, thermoplastics have low modulus. Under load, their asperities will deform measurably. Whereas, with thermoplastics rubbing against metal, it's both adhesion and deformation. Friction will decrease disproportionately more with higher load, proportionally with speed.

Here are some clues to help you find the failure mode: If you see fine debris it's an indication surface wear is adhesive-related and normal. But if you see gouges, the presence of melted polymer, wear is abrasive, P-V limits of your materials have been exceeded.

My background is coatings. Though you know these theories are applicable to materials in general. For more help, see:

<a href="

http://www.industrialcoatingsworld.com/Low-Friction-Coatings/index.html">Low

Friction Coatings</a>

Best wishes.




William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[edrush]

"Like Dissolves Like". It makes sense that this general solubility rule applies to solids too, and hence there will be more inherent adhesion between two identical polymers then there will be between two dissimilar materials. In addition, PTFE does not have very good wear resistance. I spite of it's low friction it does not make a very good bearing (depending on the speed and load conditions) simply because it does not have high mechanical proporties.