Vacuum Greases, High Performance from SPI Supplies
Selection of grease for use as a general laboratory lubricant for
glassware applications
For laboratory glassware applications, one can chose between lubricants
that are hydrocarbon based, silicones, or fluorocarbon (perfluoroether)
based materials. And for the inexperienced, it is often times a difficult
decision to make as to which would be best.
Probably the most widely used laboratory glassware lubricant is the
Dow Corning 976v, the main reason
being that it is so cheap. However, there are a number of reasons why
this might not be the best choice for specific applications. For example,
when it comes time to remove the grease, there are no real solvents to aid
in its removal. So if the surface is smooth without convolutions or
cavities, and the grease can be wiped off relatively easily, then this
would not be a drawback. But many surfaces being lubricated are not
necessarily flat and smooth and therefore, it becomes nearly impossible
to completely clean off the grease.
Apiezon AP-101 has similar
properties but since the liquid extender phase is a hydrocarbon, the grease
can be removed quite easy with any common laboratory (hydrocarbon) solvent.
It is often thought that AP 101 is a better lubricant in terms of actual
lubrication, than a silicone. And furthermore, we have found that silicones
tend to "creep" and can end up where you don;t want them where as AP 101 is
much more likely to stay where they are applied and do not exhibit such
extreme creep phenomena.
Note: Apiezon AP-100 instead
of AP-101 should be used for high vacuum applications. AP-100 is really
to the first approximation, Apiezon H
with PTFE particles added. But for either AP-101 or
AP-100, removal of the grease is accomplished readily with any hydrocarbon
based laboratory solvent.
Santovac® 5GB Ultra High Vacuum Grease can also be used
as a glassware lubricant but it might be "overkill". But it too would come
off with ordinary laboratory solvents.
The Braycote fluorocarbon based greases get the nod for glassware use when
chemical inertness is the top priority. They are more expensive but they are
also higher performance. They can be removed relatively easily through the
the use of
Fluoroclean® HE. Being essentially with the properties
of PTFE, it is inert to most materials has also possesses
good high temperature properties, some as high as 240°C.
So in the end, there is no one "perfect" grease for laboratory glassware,
but the grease ultimately selected must be done so on the basis of
performance first and price second. Nothing can be more frustrating than to
have an experiment go bad because the wrong grease was selected!
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Tuesday May 13, 2008
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