oxidative attack of polyamide components

[dom253]

Is it possible that the removal of a lubricating oil containing antioxidant additives may give rise to the nylon components within the system suffering oxidative attack. What i'm trying to say is........do the antioxidant additives in lubricant oil also act as an antioxidant film that protects components from oxidative attack..? Also, would the free radicals contributing to oxidation be neutralised by the additive , thus reducing potential for oxidative attack of the nylon components.

 

[unclesyd]

I have never encountered any situation where this question would come up. This is not saying it couldn't happen but I've never seen it. As you probably know heat is the worst enemy of Nylon as it causes it to cross-link to for a gel, which is good for nothing.
The only problems of similar nature that I'm aware of are:
A QA compound in a cutting fluid did attack some Nylon bushings.
A particular synthetic oil did dissolve Nylon after an auditive was removed

If you are working with Nylon 66 you might give these folks a call. I don't have a name as all my sources have moved on.

http://www.vydyne.com/en/Services/Default.aspx

 

[TVP]

dom253,

The answer to your question is essentially no. The antioxidants within the oil do not have a substantial antioxidant effect on polymer components that are suspended within the oil. Antioxidants prevent the formation of oxidation products like alkylhydroperoxides, dialkyl peroxides, alcohols, aldehydes, ketones, carboxylic acids, and esters. Most of these are acidic in nature, so once they are generated, it is possible that one or more of these chemical species attacks the nylon. The presence of the antioxidant in the oil thus would have a secondary effect on the oxidative attack of the nylon, not a primary one.

 

[dom253]

Thanks for that TV,

Would an oil film covering the nylon component not offer any oxidation resistance then? I have a problem of nylon components that are basically so degraded that they crumble after only 6 months in service. The same components have been used for years in an oil lubricated compressor system without effect. Now the components are being used in an oil free (water cooled compressor) and it is now we see the problem. The water used for cooling is reverse osmosis water. Is this ro water likely the accelerate oxidation without the presence of oil. (i believe the RO water has a high ORP value approx 500mV)

 

[dom253]

Unclesyd,

Could you give a little more info about the synthetic oil additive removal issue you know of?

 

[unclesyd]

As I recall it was an additive used in some light weight EP gear oil used for a small gearbox with Nylon gears. It essentially dissolved or softened the teeth where they would stripped. I'll try go get some information, but as I have stated before they have shutdown the big company library so information is getting hard to come by.

I would contact the Ascend (Vydyne) group and hopefully they will analyse the failed part even though it may not be Vydyne. They can tell who made the Nylon.

 

[EdStainless]

Back up, did you say water? What is the max internal temp?
You may be killing the nylon by it absorbing water.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[dom253]

Yes EdStainless reverse osmosis water used in the cooling, and any water from the atmospheric air that the compressor sucks in. The max temp within the system is 65 degrees c