>Larry Hoy wrote:
>
>
>>Something I've always wondered. Is the swelling of rubber brake
>>components related to the early or old rubber compounds that are often
>>found in our cars; or, is it related to using the wrong brake fluid? It
>>would seem in this day and age all fluids ought to be compatable with
>>all 'new' rubber compounds.
>>
>>What does the 'group' think about this?
>>
>>
>> If my memory serves, the older seals were Butyl rubber, man's first
>attempt at 'synthetic' rubber. The problem with butyl rubber is that it has
>few strong sulfur-sulfur bonds and therefore it is easily affected by other
>materials which have an affinity for it's ions, and can place parts of
>themselves into the structure of the rubber itself (hence the swelling, as the
>amount of material molecule-wise increases).
>>
>> The current, or modern, synthetic rubber seals are usually Nitrile,
>which has more sulfur-sulfur bonds as well as a nitrogen component which tends
>to lower the reactivity of the rubber to things like alcohols and certain
>oils. Therefore, the use of NOS seals should probably be
>avoided given the advancement in elastomeric technology and fluids technology
>as well. The newer elastomers are probably more well suited to the use of the
>newer fluids type of fluid being immaterial. If you are looking for the best
>of the newer elastomers, check out fluoropolymers, they are touted to be inert
>in many of the more aggresive environments, but they are relatively soft and
>can wear quickly if used in a sliding mode
>>
> Mark Haynes RMVR
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