Re: [T3] glycerin rubber treatment

[Jim Adney <jadney@vwtype3.org>]

On 19 Jul 2006 at 0:08, Jason Weigel wrote:

> So why is vasoline bad? Ive used it for many years with great results. It 
> has even brought life back to my original rubber on the windows. Is this 
> opinion or survaical scientific fact??

There are (obviously) some types of rubber which are fine with petroleum 
products, but most are not. The worst petroleum offenders are the most volatile 
ones, like gasoline. Vaseline is a rather heavy, non-volatile, compound which 
whose effects should be minimal.  

On type 3s, it is clear that the rubber oil filler bellows is quite happy with 
oil, but if you take a look at the rubber "gasket" under the "base" (where the 
dipstick screws in) is a perfect example of a rubber that is NOT compatable 
with oil. Those should have been made from a different material, but they 
weren't.

The bad effects consist of the petroleum compound soaking into the rubber and 
causing it to swell and soften. I suppose that a limited amount of this, like 
you might get with vaseline, might even give good results. But most of the time 
there is also a long term degradation of the rubber compound.

My resource for this is the Parker O-Ring Handbook. It is an extremely useful 
compendium of information on the properties of various rubber compounds and 
their compatabilities with lots of various fluids, as well as a listing of all 
standard US sized O-rings and design specs for designing proper O-ring grooves.

Don't ever pass up the opportunity to grab one of these.

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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