Typical Lubricants Wear and Load Carrying Ability
||4-Ball Wear Scar, mm*
||Falex Pin and V-Block Fail Load, lb
|* 20 kgf, 107°C (225°F), 1200 rpm, 60 min, 52100 steel onsteel.
** Test was stopped at 4,500 lb.
Nonflammable Krytox® lubricants contain only carbon, oxygen, and fluorine. Because hydrogen is not present, these products are nonflammable. They will not burn or support combustion, even in 100% liquid or gaseous oxygen.
Krytox® performance lubricants are not only resistant to oxygen but are inert to virtually all chemicals used in a variety of industries. They are insoluble in most solvents but are soluble in highly fluorinated fluids in some super critical fluids such as CO2.
Thermal and Oxidative Stability
The temperature at which thermal decomposition of Krytox® oils takes place depends on the test method used and how the point of incipient deterioration is measured. By differential thermal analysis, deterioration occurs at about 470°C (878°F) in the absence of air. The isoteniscope technique shows an initial decomposition point of 355°C (671°F) as measured by excess pressure increase. At 355°C (671°F), the decomposition rate is approximately 0.03 wt% per day. At 399°C (750°F), the decomposition rate increases to 1.3 wt% per day. When tested under nitrogen for 6 hr at 371°C (7000P), Krytox® showed no increase in neutralization number and no significant change in viscosity.
The presence of air does not substantially lower the decomposition point of Krytox® oils. However, in the presence of certain metal oxides, depolymerization of the oil can start as low as 288°C (5500P). During depolymerization, gaseous decomposition products are given off and the remaining fluid is less viscous, but no sludge or gummy deposits are formed.
In most applications, Krytox® oils have proven serviceable for long periods at continuous temperatures up to 288°C (5500P) and intermittent temperatures of 427°C (8000P).
Compatibility with Elastomers and Plastics
Krytox® is compatible with all elastomeric seal materials and engineering plastics. The limiting factor when using Krytox® with any material is the thermal stability of the elastomer or plastic.
Krytox® performance lubricants are compatible with the following common elastomers and plastics:
||Hypalon® Synthetic Rubber
||Nycar 100 (Buna N)
||Hytrel® Polyester Elastomer
||EPT, Peroxide Cure
|Viton® A Fluoroelastomer
||Nordel® Hydrocarbon Rubber
* 15-20 vo1% swelling at high temperatures when immersed.
Compatibility with Metals
Because of their low surface tensions, Krytox® lubricants easily wet metallic surfaces. Krytox® lubricants are chemically inert and therefore have no adverse effect on metals when the temperature is below 288°C (550°F). Above 288°C (550°F), many alloy steels, stainless steels, and other metals such as aluminum alloy, titanium alloy, nickel alloy, and cobalt alloy can be used with Krytox®.
Compatibility with Oxygen
At elevated temperatures and pressures, perfluoroalkylpolyethers are highly resistant to attack by gaseous and liquid oxygen. As a result, Krytox® fluorinated oils have become preferred lubricants in the oxygen manufacturing industry and in those industries that use oxygen.
Krytox® oils do not react with gaseous oxygen under shock loading or with liquid oxygen (LOX), nitrogen tetroxide, or inhibited red fuming nitric acid in impact tests. LOX impact tests were conducted in accordance with Marshall Space Flight Center MSFC-Spec-l 06B. Other impact tests conducted at 214 J/cm2 (200 ft.lb/in2), according to the method described in ASTM Bulletin 250, also show no reaction.
Krytox® lubricants have also been evaluated by the West German Federal Institute for Materials Testing (Bundesanstalt fuer Materialpruefung, BAM) for reactivity with gaseous and liquid oxygen under pressure.
Krytox® oils are quite stable to radiation when compared with many materials used as lubricants or power fluids. In general, irradiation of Krytox® oils causes minor depolymerization, with a consequent reduction in viscosity, and formation of volatile products but not solids or sludge. In one test, exposure of a Krytox® sample to an electron bombardment of 107 rad at ambient temperature in air resulted in a viscosity decrease of 8%. The irradiated sample contained no sludge and was unchanged in appearance.
Krytox® fluorinated oils are biologically inert and are not metabolized. They are not biodegradable and do not support any type of biological growth.
Stability to Lewis Acids
Some depolymerization of all perfluoropolyalkylethers occurs at elevated temperatures in the presence of aluminum trichloride, iron (ferric) or zinc chlorides, and boron trifluoride. These so-called Lewis acids, primarily seen in semiconductor manufacturing environments, have significantly less effect on Krytox® than on competitive fluids, due to its molecular structure. Additional data are available upon request.
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