The present invention relates to lubricating grease compositions comprising (a) at least one high-viscosity fluorinated oil having a viscosity of 500 to 1500 mm.sup.2/s, (b) boron nitride and (c) a binder selected from bentonite, alkali metal phosphates, aluminum phosphates, alkali metal silicates, alkaline earth metal silicates, aluminum silicates, alkaline earth metal carbonates, calcium borate, silicon dioxide, titanium dioxide, aluminum oxide and mixtures thereof. The lubricating grease compositions find use especially in the high-temperature sector, for example for the lubrication of oven pullout rails.

The present invention provides a polytetrafluoroethylene powder having high dispersibility in lubricants. The polytetrafluoroethylene powder includes polytetrafluoroethylene containing a tetrafluoroethylene unit alone or a tetrafluoroethylene unit and a modifying monomer unit based on a modifying monomer copolymerizable with the tetrafluoroethylene, and has a specific surface area of 32 m.sup.2/g or larger.

A grease includes a perfluoropolyether oil copolymer and a thickener mixed with the copolymer. The copolymer includes about 20 mol % to about 80 mol % of CF.sub.2CF.sub.2O units, about 20 mol % to about 80 mol % of CF(CF.sub.3)CF.sub.2O units, and about 0 mol % to about 45 mol % of one or more additional perfluoroalkyleneoxy units. The copolymer has a viscosity index in the range of about 120 to about 220. The copolymer has an average TFEO run length of less than about 6. A process of forming a grease includes mixing a perfluoropolyether oil copolymer with a thickener to form the grease.

A heating device including: a rotating member for heating, an opposing member, which is arranged so as to be opposed to the rotating member, and forms a nip portion together with the rotating member, and a biasing member, which is arranged inside the rotating member, has an opposing surface with respect to an inner peripheral surface of the rotating member, and biases the rotating member to the opposing member. The inner peripheral surface and the opposing surface are brought into contact with each other via a grease composition to form a sliding portion. The grease composition contains a base oil. The base oil contains a fluoropolymer having a specific structure and a perfluoropolyether having a specific kinematic viscosity and a specific evaporation loss and having a specific structure.

The present invention provides a polytetrafluoroethylene powder having high dispersibility in lubricants. The polytetrafluoroethylene powder includes polytetrafluoroethylene containing a tetrafluoroethylene unit alone or a tetrafluoroethylene unit and a modifying monomer unit based on a modifying monomer copolymerizable with the tetrafluoroethylene, and has a specific surface area of 32 m.sup.2/g or larger.

A sliding member according to the present disclosure contains, in a sliding layer, a synthetic resin, a solid lubricant, and an additive. The synthetic resin is a polyimide, a polyamide imide, a polybenzimidazole, a polyphenyl sulfone, a polyether sulfone, a polyether ether ketone, or a combination thereof. The solid lubricant is a polytetrafluoroethylene, a tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, a tetrafluoroethylene-hexafluoropropylene copolymer, or a combination thereof. The contained amount of the solid lubricant in the sliding layer is 5.0-40.0 vol. %. The additive is bentonite, smectite clay mineral, silica, a polyamide, or a combination thereof. The contained amount of the additive in the sliding layer is 0.1-9.0 vol. %.