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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:
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
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.
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.
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.
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.
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.
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.
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.
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.
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 ten 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 ten 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.
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.
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.
We do not recommend the use of any of the PFPE lubricants or fluids for use in the human body.
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.
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.
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