Rubber drying out ??

[corrosionman]

My Rubber Lining Company has recently been asked to line some road tankers to be used for transport of various different corrosive liquids. Rubber will be Hypalon.
During discussions with a very experienced Tanker User he said that it is normal practice that when tankers are laid up it is usual to fill them with water to stop the rubber "drying out and degrading".
Please have any of you anny comments on this one ??
Thanks in advance, David Whitlock.

 

[tomaspin]

David,

The possible mechanisms for degradation of the rubber could be either oxidation, or attack from fumes/residues left in the tank.
I assume therefore that the reason for filling the tank with water is to prevent the build up of fumes and/or to keep oxygen away from the lining.
Maybe a someone with a chemical or process enginering background would be able to give some more insight into this question.

Regards,

Tom

 

[aviat]

Synthetic rubber fuel bladders have a similar problem when used to store gasoline. One reason given from an OEM is that gasoline has a tendency to extract the plasticier from the inner liner of the cell. It is not detrimental as long as gasoline is in bladder, in as much as gasoline itself will act as a suitable plasticier. Removing the gasoline removes the plasticier effect and the inner liner dries out and cracking can occur, allowing gasoline to diffuse out. It occurs after 10 days without fuel and they recomend using light oil to keep them soft. It also makes the bladders easier to work with.

 

[Elastoman]

Another means of preventing or drastically reducing the extraction of plasticizers is to compound the rubber with polymeric (high molecular weight) plasticizers. This is commonly done for rubber parts that are in contact with fuel or solvent based materials.

There may be other rubber compounds that would be more suitable than hypalon. NBR is known for having exceptional fuel and oil resistance and normally is less expensive than hypalon.

 

[ElastomerXpert]

Filling a Hypalon-lined tank with water seems a bit strange, Hypalon is not usually compounded with lots of plasticizer and ages very well. (Much better than nitrile.)The comments others made about some hydrocarbon fluids extracting plasticizer (and sometimes other ingredients) from rubber are valid, but Hypalon should be less subject to that, and in any case, water won't put anything back into the rubber that other fluids took out. You may well be hearing well-intentioned but inaccurate advice.

R J Del Vecchio
Technical Consulting Services
(consultant in Applied Rubber Technology)