Additives II - Seal Swell

[MolaKule]

Ok, this one may be a bit tougher.

Various organic Phosphates, Nitriles, aromatic hydrocarbons, and esters have been developed to affect:

1. what component in an engine or transmission, or hydraulic systems?

2. And how does it affect this component?

[ July 22, 2003, 01:29 PM: Message edited by: Patman ]

 

[jason07-1zzfe]

1) seals

2) swell/conditioning/stop leaks ...
Except nitrile is a rubber compound I thought, so that would be seal material I guess.

 

[Pablo]

I agree with Jason - but why the Nitriles? (please define nitrile)

Phosphates? To clean seals?

Why do esters cause slight seal swell?

 

[Schmoe]

I'd say cleaning, for 200 Alex. Has to do with keeping the engine/trans/hydro cleaner.

 

[68redlines73]

1) Seals (noun)

2) Seals (verb)

 

[MolaKule]

Here is a partial answer embedded in this thread:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=000156;p=2

[ June 02, 2003, 04:46 PM: Message edited by: MolaKule ]

 

[MolaKule]

These are all seal conditioners, which work by one or more of these methods:

1. Cleaning the seal,
2. swelling the seal slightly by replacing elastomer molecules.

In 1980, Lubrizol patented a seal swell additve using "beta-thiopropionitrile" chemical which replaces the nitrile atoms lost to wear, oxidation, and sludge encroachment.

In addition, the ester di(2-ethylhexyl)-adipate (a di-ester), or similar ester equivalents, are often added to PAO and Group III base fluids, at about 5%, to improve seal swell.

[ June 02, 2003, 11:20 PM: Message edited by: MolaKule ]

 

[Pablo]

Excellent question I might add!!! Short and very informative answers!

 

[MolaKule]

quote:

---

I agree with Jason - but why the Nitriles? (please define nitrile)

---

Nitriles are synthetic hydrocarbons which make up a class of elastomers, or synthetic rubbers. Most nitriles are used in making seals and sealing products.

 

[Pablo]

Thanks Mola - that's what I thought (I usedta do compatability tests with seal materials and of course nitriles was involved)- exceptn'fore never hearda "beta-thiopropionitrile"....

 

[MolaKule]

Some seal info we posted in another thread:


In common use of the terms, Swelling indicates an increase in volume, whereas Shrinkage is a decrease in volume.

Increasing the volume (swelling) of a simple "O" ring type seal, for example, causes the ring's inner diameter to decrease, since the donut is becoming larger.

Decreasing the volume (shrinkage) causes the inner diameter to increase.

In most cases, the outer dameter of course is always fixed, as in automotive shaft seals.

Many esters are used in the manufacture of seals as "plasticizers."

Plasticizers are used to increase the flexibility of materials that would otherwise be "inflexible."

 

[MolaKule]

Most ATF seal swell agents are composed of esters:

tris (C8-C24 hydrocarbyl) phosphite ester

Bis(2-ethylhexyl) ester phosphoric acid

Dihexyl Phthalate ester

and the azelamides such as:
N,N'-dimethyl-N,N'-dihexylazelamide, N,N'-dimethyl-N,N'-di2-ethylhexylazelamide, N,N'-dimethyl-N,N'-di-2-ethylhexylsebacamide

 

[JHZR2]

The question I have now is, in a properly working AT, for example, what effect do these agents have on the seals? Why swell them if they are operating fine? Could seal swell agents create undue stress or premature failure of seals???

 

[MolaKule]

See if this thread answers your question:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=530741&page=4

 

[Cmarti]

Originally Posted By: MolaKule
See if this thread answers your question:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=530741&page=4


Sigh....Dad is a Chemist, son graduates in Chemical Engineering this spring. It proves that intellect skips a generation and that thread did not answer the question within my limited ability to comprehend. I am a wrenchhead though. I can do a rebuild, I just can't do a bonding orbital diagram.

Seal conditioners work in a couple pieces of old equipment I have. The flow is not detrimental, they are not of great value, and I am too lazy to tear apart at this time. As an additive or in a HM oil, they have reduced or eliminated slow weeping. Is there any long term damage to seals/gaskets when used as recommended?