Fluorosilicone greases vs. Silicone greases 1

[PratsA]

One of my main projects at my company is to reduce our inventory of adhesives and other chemicals. I've been asked to look at our lubricants and try to cut down on what we use.

In particular, I'm comparing Molykote 3452 (fluorosilicone base with ptfe filler) and Parker Super O-Lube (conventional silicone grease). The molykote's viscosity is almost a factor of ten lower than the O-lube, but otherwise the only difference seems to be the base.

In general, it looks like fluorosilicone lubes have all the advantages of silicone lubricants, plus other advantages like:
They will not swell silicone o-rings
Higher load capacity for metal-metal contact
Effective at lower speeds
Better chemical resistance

I'm not finding out what the disadvantages are. Other than cost, is there any reason to prefer a silicone based grease like O-Lube over the fluorosilicone grease?

 

[coatingengineer]

Hi. So many questions come to mind. For example, are you at one atmosphere, or are you under vacuum? Is there potential for a boundary-lubrication condition? What are the contacting surface metals?

Generally, a higher viscosity grease should ensure a better, more consistent stream of oil. Assuming the thickener doesn't get in the way of the lubrication, in which case you would have noise. Both choices in oil type are comparatively low volatility, so lubricant retention in terms of evaporation should be acceptable. My only question for DOW (Molykote) is if, under boundary contact, fluorine will react with the surface, iron for example, create a catalyst and promote polymer degradation.

If you need more information on how to choose a low friction coating, I'd be happy to help you at:
<a target="_new" href="

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

Friction Coatings</a>

Best wishes.




William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[PratsA]

When you say a higher viscosity of grease, what do you mean? I've been trying to understand the relationship - if any - difference between NLGI consistency, base oil viscosity, and the effect of thickeners.

The current application involves o-ring lubrication, the majority of which are buna-n, some viton, a potential for silicone in the future. Most o-rings are static but a few are used to seal areas that will be rotated back and forth at very low rpm. The o-ring is sandwiched between steel, or steel/aluminum, or aluminim/UHMWPE. Room temperature, 1 atm use, with short term exposure to chemicals and/or high pressure steam for cleaning between uses. Not user-serviceable, but will be recovered and remanufactured a few times, at which point the seals will be replaced and relubed. Money is never not an issue, but these come close.

From the research I've been doing it's looking like there's no reason to not use the fluorosilicone, but I'll be glad to hear any other ideas

 

[coatingengineer]

Hi. First, I have to say your choice of any silicone-based grease is spot on for lubrication between plastic and steel. NLGI defines "consistency" (ASTM D 217) by the cone penetration test. Maybe not much help other than to suggest a grade number, determined from your "DN" value (diameter x rpm). For low speed, yes, choose the higher viscosity oil. If your thickener is aluminum, based on the need for high chemical resistance, that's a plus. In summary I'm siding with you, PratsA. Your choice of the fluoro-silicone product makes perfect sense.

Thanks for posting.






William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[PratsA]

Thanks for the tip on aluminum. I will keep reviewing my options. Your advice was very helpful.

 

[coatingengineer]

You're welcome, PratsA. Where I can, I'm always glad to help.

William Gunnar

http://www.IndustrialCoatingsWorld.com