Finding the right alcohol-proof rubber

[PeteB]

On 6/6/2017 at 9:50 PM, Spitfire said:

A quick update on this topic, I finished another test this time with a silicon gasket and got same result although less cloudy than the other tests (see photo)  

I started another round of tests by washing all previously tested gaskets (nitrile, viton) and adding some fresh GNS in a small jar for a week, we'll see how it goes.  Also, a new test this time with a neoprene gasket.

 

What was the result when/if you re-tested the gaskets?

[Spitfire]

The last tests we did were not conclusive, we could not find any rubber material that did not introduce cloudiness into alcool when immersed for a couple of days.  We changed our procedures to prevent any situation where high-proof alcohol is in contact with rubber material for a long period of time.  

[bluestar]

On 12/17/2018 at 9:56 AM, Southernhighlander said:

You make a good point concerning sulphur cured EPDM at high temps and I should have pointed that out, but my charts show that peroxide cured EPDM is good for alcohols up to 300 F.  We only sell the peroxide cured,  but we do not put EPDM gaskets in any of our equipment.

Theoretically that is true. BUT, we did tests and found that while the peroxide cured EPDM gaskets don't appear to degrade in performance as gaskets, it does allow a small amount of leachate to be picked up by the spirit if the EPDM is downstream of the still head in the path of high-temperature, high-proof spirit (like between the dephlegmator and the condensor). For that location, we use platinum-cured translucent silicone. These might toughen a bit over long use, but they hold up to temperature, and we don't observe any leachate.

[Southernhighlander]

Blue star,

 

Thanks for pointing that out.  I will stop selling them for ethanol stills.   We are supposed to be able to trust our chemical compatibility charts.