Nylon 6 Grease or Lubricant ??? 2

[ornerynorsk]

Hello All,
We have an application in which Nylon 6 with 33% glass is being used as a bushing material. Shaft material is carbon steel, a mixture of stressproof and precision ground shoulder bolts. The motion is reciprocal rotation of maybe 40 to 50 degrees at most. Duty time is 20 to 30 minutes with a frequency of 15 to 20 cycles per minute. Duty time is repeated in various intervals up to a half dozen times per day. After several months of being in service, these things start to squeak terribly. We are not exceeding PV values. We have tried them dry and with "typical" cheap red lithium grease, same result. Any recommendations on a grease or lubricant that is compatible with nylon? Application is in hospital rehab equipment, so we can't have oils bleeding all over. Thanks everyone!

 

[Demon3]

You should buy nylon that comes filled with solid lubricant. Such grades are commonly available for example see

http://www.matweb.com

You can get nylon filled with MoS2, graphite or oil for example.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[ornerynorsk]

Thanks, but Molydisulfide has proven itself not to work either. Dry lube additive or compound seems to not have the surface properties of a wetted surface or film.

 

[Demon3]

Yes, but it works much better when it's in the nylon, not added on the surface later. As the nylon wears, new lubricant is released automatically. That's why those special grades of lubricant filled nylon exist.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[Compositepro]

I don't believe that glass-filled nylon is suitable as a bearing material. Glass is very abrasive.

 

[Demon3]

Maybe carbon fibre filled or talc filled would be better then.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[patprimmer]

The options for a bearing in reinforced nylon are.

Glass fibre filled, OK until the surface wears then exposes the glass, then terrible.

Mineral filled. Better than glass re wear, but much lower physicals.

Aramid pulp filled. Great wear resistance, moderate physicals and abrasive on mating surface.

Aramid fibre filled. Very good physicals but abrasive on mating surface.

Carbon fibre filled. Great bearing. Great physicals. Real expensive.

Unfilled heavily nucleated. Great bearing. Moderate physicals.

Non-reinforced, heavily nucleated, solid lubricant filled. Best bearing. Moderate physicals.

For non-reinforced nylon, Molybdenum and graphite gives best results ad the moly nucleates very very well, and the graphite gives a very effective dry lubricant.

Why is the glass there.

Unfilled nylon 4.6 or Stanyl may be a good choice, depending on overall balance of properties required.

Graphite and molly filled nylon 6.6 is typically used as the bearing pad in automotive engine timing chain tensioners.

Nylon 6 has to low a softening temperature for this application.

Nylon 4.6 has a much higher softening temperature and replaces nylon 6.6 in difficult applications.









Regards

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[Demon3]

Had to star that one Pat. Thanks for the valuable post and mini lesson. I need to get you to write a book.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[dwightdixon]

If he needs the physicals offered by the glass reinforcement but can not stand the glass on the bearing surfaces, He might try insert molding over a teflon filled nylon bearing liner to still make it a single piece. Otherwise a liner is not difficult as an assemble going over the bolt before putting on the structural glass filled part.

 

[ornerynorsk]

Thanks everyone. Your information has been very helpful.