High Temperature (XHT)
Krytox XHT lubricants are ideal for extra high temperature applications (204-399°C or 400-750°F). Unlike conventional mineral oil or even alternate synthetic lubricants that degrade quickly elevated temperatures, Krytox XHT greases are stable, nonflammable, non-volatile and oxygen compatible. Extended relubrication cycles or replacing recirculating oil systems can save 10-100x plus the cost of the lubricant. XHT is available in a variety of grades for specific applications.
XHT-S and XHT-AC: The most economical high temperature greases. Use below 320°C (608°F). XHT-S is an extension of GPL 20X greases (originally called GPL 207-500). XHT-AC is an extension of GPL22X greases (originally called GPL227-500).
XHT-SX and XHT-ACX: These greases are similar to their counterparts above but with much lower vapor pressure. XHT-SX is an extension of the Aerospace 240 series greases. XHT-ACX was previously called LVP-228.
XHT-BD, BDX and BDZ: These are extreme high temperature greases designed for use where temperatures are up to 300°C with intermittent spikes up to 330°C (BD) or even 400°C (BDX, BDZ). These greases are extremely viscous, slightly tacky, and will coat surfaces and stay in place
Selection of the best lubricant involves analyzing operating conditions and choosing from the many synthetic and petroleumbased products available today. While most petroleum products begin to degrade before 99 °C (210 °F) and cease turning at temperatures just below –18 °C (0 °F), DuPont™ Krytox® fluorinated synthetic lubricants have operating ranges that are significantly broader (–70 to 316 °C [–94 to 600 °F]).
Krytox® lubricants are more effective at even higher temperatures, regardless of operating duration. Using base oils, thickeners, and additives with chemistry designed to create high and low viscosity, these products are targeted for use solely in the very high-temperature range. Available in several grades that offer anticorrosion, extra bonding, and non-melting properties, these lubricants have applications in a variety of industries, including chemical, textile, tire, aviation, conveyor, glass, plastic film, nonwoven manufacturing, and mining and metal processing.
Because of its thermal stability and nonoxidizing characteristics, Krytox® is a natural high-temperature lubricant. Krytox® XHT greases are available with useful temperature ranges up to 360 °C (680 °F) for continuous use, with spikes to 400 °C (752 °F), when used in proper metallurgy with periodic relubrication.
DuPont™ 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 and in some supercritical 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 six hours at 371 °C (700 °F), 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.
During depolymerization, gaseous decomposition products are given off, and the remaining fluid is less viscous, but no sludge or gummy deposits are formed. DuPont™ Krytox® XHT LUBRICANTS Krytox®