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Drying or coking of high-temperature bearing grease does not necessarily mean that the base oil lacks temperature resistance. Base-oil evaporation and oxidation, changes in thickener structure, relubrication practices, actual bearing temperature, speed and load may all contribute to failure. Phenyl silicone oil, synthetic hydrocarbons and PFPE have different operating boundaries; selection should not be based on a single “maximum temperature” value.
Grease consists of a base oil, a thickener and any necessary additives. Drying during operation may result from:
Replacing only the base oil without checking the complete grease system may therefore leave the problem unresolved.
At minimum, confirm:
A specific base oil or grease grade should not be selected when these conditions are incomplete.
Phenyl silicone oil can be evaluated as a base oil for high-temperature lubricating oils or greases. Compared with conventional dimethyl silicone oil, some phenyl-modified silicone fluids exhibit different high-temperature oxidation stability and metal-lubrication behavior.
Suitability must still be verified through viscosity, bearing load, friction and wear, thickener compatibility and evaporation-loss testing.
Synthetic hydrocarbon base oils are used in many industrial bearing-lubrication systems and offer different options regarding lubricity, additive compatibility and cost.
At high temperature, oxidation, evaporation, viscosity increase and deposit formation must still be assessed. High-temperature service life cannot be predicted from room-temperature viscosity alone.
PFPE lubricants may be evaluated for high-temperature, vacuum, clean, strongly oxidizing or chemically demanding environments. Some PFPE greases are used in high-temperature, vacuum or oxygen-rich equipment, but such performance belongs to specific formulations and test conditions.
PFPE generally involves higher material and qualification costs. An ordinary industrial bearing does not necessarily require PFPE unless its cleanliness, chemical-stability or temperature requirements justify it.
No. Published lubrication literature indicates that conventional PDMS has lubricity limitations in some metal-to-metal applications. Phenyl-methyl silicone fluids, fluorosilicone fluids and alkyl-modified silicone fluids may behave differently, but the tribological pair, load and speed must still be verified.
For bearings operating under heavy loads, impact or significant boundary lubrication, the base oil alone may be insufficient. Anti-wear additives, solid lubricants or other lubrication systems may also need evaluation.
The same base oil combined with different thickeners can produce very different grease performance. Evaluate:
A high dropping point does not mean that a grease can operate continuously near that temperature.
Continuous temperature, short-term peak temperature and test conditions must be distinguished.
Phenyl silicone oils offer relevant thermal-stability characteristics, but contamination, overheating, unsuitable formulation and metal-catalyzed reactions may still change their performance.
PFPE must also be matched to speed, load, thickener, tribological pair and cost. It is not required for every machine.
Grease failure may also originate from the thickener, additives, relubrication method or bearing design.
Different thickener systems may soften, harden or separate when mixed. Compatibility should be confirmed before changing grease; the original lubrication system should be cleaned when necessary.
First, confirm the bearing’s actual temperature, speed, load and surrounding media. Second, determine whether the old grease failed through evaporation, oxidation, leakage or thickener breakdown. Third, compare phenyl silicone oil, synthetic hydrocarbons, PFPE and other candidate base oils. Fourth, match the thickener and any necessary anti-wear system. Finally, verify high-temperature operation, evaporation, oil separation, wear and material compatibility before confirming the solution.
As a global silicone solutions provider, IOTA Silicone Oil (Anhui) Co., Ltd. can assist in screening phenyl silicone oils and other specialty functional silicone fluids for high-temperature lubrication. If the actual load, medium or cleanliness requirements favor another material, it should also be included objectively. No grade should be specified before the operating conditions are sufficiently defined.
No. Base-oil oxidation or loss, thickener changes, insufficient relubrication and local overheating may also cause drying.
Some phenyl silicone oils can be considered, but viscosity, evaporation, friction and wear, thickener compatibility and bearing conditions must be verified.
The comparison cannot be made without specific products and test conditions. PFPE suits certain extreme environments, but load, speed, thickener and cost still matter.
No. The dropping point indicates a state change under specified test conditions and cannot be used directly as a continuous-service temperature.
This cannot be assumed. Conventional PDMS has lubricity limitations in some metal-to-metal applications, and heavy-load service requires friction and wear testing.
If the old and new greases use different base oils or thickener systems, compatibility should first be confirmed. If it cannot be confirmed, remove as much old grease as practicable before introducing the new grease.
