28 year old rubber

JHZR2

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Hello, I want to condition the rubber on my 1981 MB 240D. It is 28 years old, obviously, in very good condition overall, but in a few spots looks like it is starting to develop small cracks. Ive done all the reading about silicone, petroleum distillates, etc., but it seems that most of the discussion and conversation focuses on modern silicone rubber. Would a 28 year old car use silicone rubber or would there be a potential for natural rubber to be used? Would the age or potential composition change the products to be used? Krytox and 303 are my choices. Thanks!
 
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Wow. I guess my mind is in the gutter but I thought you were worried about getting your girlfriend knocked-up.
 
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Kestas

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Silicone is expensive. I work with guys that design powertrain seals, and I can't remember any designs that use silicone in the seals. If they don't use silicone elastomers in such important places as powertrains, then I doubt they are used elsewhere where parts are less critical and have a higher volume of elastomers. I'm not an elastomers expert, but the elastomers used in the powertrain are butyl rubber, HNBR, nitrile, viton, teflon, fluoroelastomers, and others. I imagine the body hardware uses something cheaper, and closer to rubber.
 
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In one word - KRYTOX. If you need some I can send you some in a small bottle to test out. (I'll do that for you )I've got 1/2 gallon of the stuff.
 

JHZR2

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 Originally Posted By: Kestas
Silicone is expensive. I work with guys that design powertrain seals, and I can't remember any designs that use silicone in the seals. If they don't use silicone elastomers in such important places as powertrains, then I doubt they are used elsewhere where parts are less critical and have a higher volume of elastomers. I'm not an elastomers expert, but the elastomers used in the powertrain are butyl rubber, HNBR, nitrile, viton, teflon, fluoroelastomers, and others. I imagine the body hardware uses something cheaper, and closer to rubber.
Interesting... So it seems like a "base" rubber, or a cheaper, lower-grade rubber would likely have been, and would STILL be used in modern vehicles. I suppose my thought is would the chemistry have changed along the years in the interest of higher UV resistance or whatnot, that would make the treatment products of choice differ. It seems that silicone, in and of itself, is OK on most any of the rubbers you listed, at least this seems to be the claim on some of these products. I have no issue using krytox if it truly is compatible with butyl rubber, HNBR, nitrile, viton, teflon, fluoroelastomers, and others, and thus can be used with all.
 

JHZR2

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 Originally Posted By: GMBoy
In one word - KRYTOX. If you need some I can send you some in a small bottle to test out. (I'll do that for you )I've got 1/2 gallon of the stuff.
Thanks!
 
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Nice car! Contrary to many, I love that late 70's early 80's German car look. And that paint color-awesome!
 

Kestas

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I've seen charts that list different elastomers and their compatibility with different fluids. I'm not sure where to access it though.
 

JTK

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+1 to the Krytox if you want the best of the best. A small tube goes a long way. OTOH, I realize inexpensive silicone spray is loaded with petroleum distillates, but that's what I've used for a good 25yrs on my vehicles without issue. Joel
 
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EPDM is used for door seals, sunroof drains, glass run channels, hood-to-cowl, etc. Krytox is compatible with EPDM & pretty much everything else. GMBoy, Which Krytox did you stumble across - 240 AC vacuum grease or what?
 
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JHZR2 - dropped the Krytox in the mail this morning. benjamming - the Krytox I have just says Krytox performance lubricants by Dupont on the front and this on the back: "High performance lubricants beyond your highest expectations" and "perflouropolyether CAS#60164-51-4. MADE IN USA" The jug is clear and its a fluid not a grease.
 
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Are there any retailers that sell a small quantity of Krytox at a reasonable price? I've found 1/2 kg of the stuff for under $60 (without shipping). The 2 oz. bottles seem to be $30-$50. How do you apply it? What do you use to clean the weatherstrip before (and after) you apply the Krytox?
 
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