Braycote® Vacuum Greases
Vacuum greases with outstanding performance under conditions of extreme
temperatures and chemical environments
Braycote® Greases
The Braycote line of high vacuum greases has been developed to cover a wide
range of temperature and chemical environments. The Braycote greases are
perhaps best known for their high chemical inertness which derives from their
basically completely fluorinated chemistry, both in terms of the "base
liquid", which is very similar to a diffusion pump fluid, and the solids
phase, which is a micro-colloid of tiny polytetrafluoroethylene (PTFE) "dispersion"
particles.
The Braycote line of greases cover a very wide range of applications and
consequently, a large number of different products, often times varying only
slightly, but having large differences in certain applications. The product
range has been very confusing for many who have approached it for the first
time, so let us try first to clarify some of the important points:
Micronic® Designation:
If a grease is designated as "Micronic", for example, there is Braycote 803
and there is also Braycote Micronic 803, this means that the grease has been
extruded through a screen pack filter to remove any PTFE agglomerates
larger than one µm. Generally speaking, the Micronic form of the same
product is more uniform and homogeneous and when applied to "O" rings, for
example, in an electron microscope, the final remains of the lubricant are
much less "gritty" than would be the case for Braycote 803. That is why for
the electron microscope application, there is a preference for the Micronic
form of the product.
Cost: Generally speaking, the Micronic form of the same product is
slightly more costly than the same product in the non-Micronic form
Effect of Braycote greases on "O" rings:
Generally speaking, the more common materials used in the construction of "O" rings
are pretty inert exposed to any of the Braycote greases. However, one does have to
be careful when the "O" ring is a fluoropolymer itself, for example, PTFE,
particularly when used at temperatures above 150°C. There will not be anything
like a chemical reaction, but the "O" ring can start to act like a "sponge" for
the base oil, leaving a pile up of the grease thickener on the outside of the "O"
ring. The solution is to presoak the "O" ring in the base oil prior to installation.
This will saturate the "O" ring and reduce greatly the rate at which additional liquid
is soaked up by the "O" ring.
Sometimes for really critical applications, only an ultrathin layer of the grease is desired on the
"O" ring and
this is done using a process known as grease plating.
There has been compatibility testing done by some of the seal manufacturers
using PFPE greases with silicone and fluorosilicone compounds. The
materials were found to be compatible. However, as expected, there can be
some minor changes to the seal/"O" ring properties, i.e. slight changes in
hardness, tensile strength, elongation, and volume. It is always
recommended that for critical applications, the customer do their own
evaluation and testing of the intended Braycote product for compatibility in
their specific application since the ultimate decision on appropriateness in
a given application rests solely with the customer and not with SPI Supplies.
Environmentally Friendly, the "EF" designation:
Some Braycote grease products have an "EF" designation for example, Braycote 601EF
or 602EF. This designates that it is a reformulated product from what
was at one time products with designations of Braycote 601 and Braycote 602.
The reformulation was done to take advantage of newer and
more environmentally friendly
manufacturing processes, but at the same time, the
product itself, in some very subtle ways, is not quite the same as the
product it was replacing. To our knowledge, anyone using, for example, the
older and original Braycote 601, could probably make a plug-in compatible
substitution with Braycote 601EF. But the user should be aware that there
are some subtle differences and that you should do the needed testing to
make sure that the "EF" form of the product will indeed work just as well in
your products as the original product.
Rust Preventative, the "RP" designation:
For some applications, it is desirable to incorporate into the vacuum grease
solution, a rust preventative and those greases that have an "RP"
designation after the product number, are those that have had this additive
incorporation into the formulation. Such an additive would not, in general,
add value to a static "O" ring type application. But it could add value in a
situation where moving parts were involved. One should not in general, use
the RP version of a formulation unless it is truly needed because some of
the other desirable characteristics, for example, ultimate vapor pressure
and weight loss characteristics are reduced slightly. Not all products are
available with the "RP" designation.
Use of antioxidants in Braycote lubricants:
None of the Braycote lubricants contain anything even remotely resembling an
antioxidant additive. Why? Because PFPE's do not oxidize! Except for the
"rust preventative" type of additive mentioned above, the entire family of
Braycote lubricants is additive-free.
Compatibility Considerations:
The Braycote family of high vacuum greases has been formulated to be, in
general, compatible with LOX\GOX (liquid oxygen/gaseous oxygen) and all
forms of chlorine. So far as we know, no reaction will occur. However,
this statement should not take the place of your own testing should there be
even the slightest possibility that this statement might not apply in your
own specific situation and system.
So while the entire family of Braycote greases are LOX and GOX compatible,
Braycote 631RP is preferred by those who do not require low vapor pressure
characteristics since it is a lower cost option. But for those needing outstanding
vapor pressure characteristics, Braycote 601EF is the preferred product.
For example, the combined features of LOX compatibility with outstanding
vapor pressure characteristics are why Braycote 601EF is used so widely
in aerospace.
As a class, the Braycote high vacuum greases are compatible with most
commonly utilized materials, plastics, and elastomers. However, the
lubricants may be adversely affected by Lewis Acid catalysts such as
aluminum chloride, at elevated temperatures. Newly exposed rubbing surfaces
of aluminum, magnesium and titanium alloys may react with these products as
well. It is always the responsibility of the user to thoroughly investigate
any applications where these problems could occur.
Fungi growth resistance:
For long term use under conditions of high humidity, one must be concerned
about fungi growth possibilities in the grease/lubricants being used. The
greases are 100% free of any hydrocarbons and the fully fluorinated
structure, both liquid and solid phases just will not support fungi growth
and therefore meet the test of being fungi resistant. For further
information: Military application, Spec MIL-HDBK-454A, Table 4-I. Fungi
susceptibility of materials.
If you do not see the Braycote product you
are looking for, let us know, because this section is still being
constructed and chances are we can get whatever Braycote grease you require.
Radiation resistance:
We are asked this question more and more frequently. We apologize for not having better
information. However, we do know about one study performed some years ago in which a
Z fluid, possibly Brayco 815Z, was exposed to gamma radiation from a Cobalt 60 source.
After exposure at 50 mrads the oil showed a weight loss of 0.1% and a viscosity decrease
of 30%. There was no apparent formation of sludge or polymeric material. This is the
only data we know about that deals with radiation exposure.
Lithography applications:
As indicated above, there does not exist, to our knowledge, information
about radiation resistance. But for those doing lithography, outgassing and
the presence of silicones seem to be the greatest concerns. The outgassing
properties of all of the Braycote products are excellent. And we are happy
to report that none of the Braycote greases contain any silicones.
Shelf life considerations:
This is a commonly asked question and there is no easy answer. In general,
these products are quite stable, and the manufacturer Castrol, will
guarantee all of the Braycote products shown on this page, in unopened
containers, for twenty years. The lubricants themselves are quite stable
chemically, but physically, with the passing of time, there can occur a
separation of the liquid phase with the PTFE solids phase.
The twenty years does not apply if the container has been opened or if an
unopened container has not been stored according to instructions.
If you should have a critical application, and if you have a large supply
left over from a previous order, then it can be recertified, for a nominal
fee. Send us full information via our
Ask a Question or Make a Comment
form and we will respond with information about cost
and turnaround times. Generally speaking, unless you have more than one
pound of the lubricant for recertification, it is
cheaper to just purchase new material. For some of the lower cost greases,
that "cross over" point might be closer to 2
pounds. Just remember that for non-critical applications, even if you do
see some oil separation, after some mixing, the grease
can be brought back to essentially its original specifications. Now this is
not the official recommendation of the manufacturer,
it is just our own experience over the years when confronted with older
material for which there has been oil separation.
Removal of unwanted grease from grease applied surfaces:
The composition of this product is a mixture of small PTFE particles
(which won't dissolve in anything) and a perfluorinated polyether liquid.
We have found that
Castrol® Fluoroclean™ HE is an
effective solvent for the liquid component of the formulated composition
and aids in the removal of the grease from places where it is no longer
needed or wanted.
Physical stability, which is something often times overlooked by the most
seasoned of engineers should also be taken into consideration. The Braycote
greases are all two (or more) phase systems and eventually the different
phases will separate out, resulting in heterogeneities in the grease. But
keep in mind that this kind of separation, which is thermodynamically driven,
is like death and taxes: You can't do a thing about it. But fortunately,
the separation rate is very slow, and it can even be slowed down by storage
of the grease product under refrigerated conditions.
pH values:
The determination of pH is not normally a test that is run on any of the Braycote PFPE products.
We can report, that on the base oil for Braycote 601EF,
there is run a test to determine the Neutralization Number which is reported in mg KOH/g with typical values
of 0.02. We are of the opinion that a neutralization test provides a better indication of levels of acid
than pH. When pH values have been run, not on Braycote products but on other PFPE oils of similar
chemistries to the Braycote 815z, the values typically have been in the 5-6 range.
Medical applications:
We do not recommend the use of any of the PFPE lubricants or fluids for use in the human body.
Additional critical information about compatibilities and solubilities:
All Braycote greases are a two phase system consisting of PTFE particles
dispersed in a "base liquid". The information below pertains to the base
liquid and not to the PTFE particle portion of the formulation.
Recently discontinued products:
From time to time, as markets change and other circumstances arise, products
are discontinued. The following products have been recently discontinued and
are no longer available: Brayco 812, Braycote 603EF . Our stock is zero on
these products but we will try to work with you to determine the appropriate
substitute for your application. In most cases we are recommending
Brayco 815Z as a replacement to Brayco 812, unless the application is at a
temperature above the range specified for Brayco 815Z.
Listing of products:
Vacuum Greases
Braycote
- 600EF
- 601EF
- 602EF
- 615
- 631A
- 631RP
- 640AC
- 640ACMS
- 803
- 803EP
- 803RP
- 804
- 806
- 806RP
- 1616
- 1624
- 1625
- 1632
- 1636
Braycote Micronic
- 600EF
- 601EF
- 700
- 701
- 803
- 1613
Brayco Micronic
- 815z
Microcote® Products
- 096, 196, 296
- LVP
Brayco Base Oils
- 812
- 814 (Micronic)
- 815z
- 849
- 1624
- 1625
- 1721
- 1721 PLUS
- 1722
- 1723
- 1723 PLUS
- 1724
- 1724 PLUS
- 1726 PLUS
- 1727 PLUS
- 1728
- 1729
Cleanroom Greases
- Optitool 215-2
Related Products
- Fluoroclean™ HE
- Fluoroclean™ X-100
- Endurex LRP
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Wednesday May 14, 2008
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