The present invention provides a class of halogen-containing synthetic base oils, and preparation method and use thereof. The synthetic base oils have introduced with halogen, especially fluorine, wherein the dipole motion of the halogen groups results in dipole interaction between the dipoles of other components and the base oil molecules of dipole-dipole and dipole-induced halogen (especially fluorine), and the interaction force is stronger and more localized than the dispersion force between the molecules of pure hydrocarbon synthetic oils, and thus the performance of the base oils is directly affected. It solved the problem of oil solubility of pure hydrocarbon synthetic oils, and also improved the properties of oxidation resistance and thermal stability.

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

Disclosed are materials that possess both low adhesion and the ability to absorb water. The material passively absorbs water from the atmosphere and then expels this water upon impact with debris, to create a self-cleaning layer. The lubrication reduces friction and surface adhesion of the debris (such as an insect), which may then slide off the surface. The invention provides a material comprising a continuous matrix including a polymer having a low surface energy (less than 50 mJ/m.sup.2) and a plurality of inclusions, dispersed within the matrix, each comprising a hygroscopic material. The continuous matrix and the inclusions form a lubricating surface layer in the presence of humidity. The material optionally contains porous nanostructures that inject water back onto the surface after an impact, absorbing water under pressure and then releasing water when the pressure is removed. The material may be a coating or a surface, for example.

A lubricant material for assisting machining process comprising a polyethylene oxide-polypropylene oxide copolymer having a weight average molecular weight of 5.010.sup.4 or more and 2.010.sup.5 or less.

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

A solid-state lubricant composition is disclosed. The solid-lubricant contains graphene, an oxide of a metal, and one or more polymeric binders. A method of making a solid-state lubricant coating on various substrates is disclosed. The method includes the steps of making a homogeneous slurry comprising powder of an oxide of a metal, graphene, and a polymeric binder with organic volatile solvent; coating a substrate with the homogeneous slurry with desired thicknesses; and drying the slurry on the substrate naturally or applying additional heat, resulting in a solid lubricant coating on the substrate. Substrates with coated solid composite lubricant show wear reduction and lower coefficient of friction compared with uncoated substrates.

A fluorine-containing ether compound of the present invention is represented by Formula (1).
R.sup.1CH.sub.2R.sup.2CH.sub.2R.sup.3(1) (In Formula (1), R.sup.1 is an organic end group having 3 or more carbon atoms which includes two or more polar groups with each polar group being bonded to different carbon atoms and the carbon atoms to which the polar groups are bonded being bonded to each other via a linking group including the carbon atoms which are not bonded to the polar groups, R.sup.2 includes a perfluoropolyether chain represented by Formula (3), and R.sup.3 is a hydroxyl group or R.sup.1)
(CF.sub.2).sub.y1O((CF.sub.2).sub.yO).sub.z(CF.sub.2).sub.y1(3) (In Formula (3), y represents an integer of 2 to 4, and z represents an integer of 1 to 30).

A solid-state lubricant composition is disclosed. The solid-lubricant contains graphene, an oxide of a metal, and one or more polymeric binders. A method of making a solid-state lubricant coating on various substrates is disclosed. The method includes the steps of making a homogeneous slurry comprising powder of an oxide of a metal, graphene, and a polymeric binder with organic volatile solvent; coating a substrate with the homogeneous slurry with desired thicknesses; and drying the slurry on the substrate naturally or applying additional heat, resulting in a solid lubricant coating on the substrate. Substrates with coated solid composite lubricant show wear reduction and lower coefficient of friction compared with uncoated substrates.

A sliding member having a coating film and a method for forming a coating film, which can realize both of improvement in lubricity of the coating film by using a solid lubricant and improvement in adhesiveness of the coating film to a ground, and a method for forming a coating film.

Disclosed is a component-replaceable water ring vacuum pump in which inner components within a head unit may be disassembled and replaced without separation of the head unit from a main body, thus shortening an operation time and improving operation efficiency through prevention of leakage of an inner liquid during a replacement process. The water ring vacuum pump includes a main body provided with a shaft, a rotor rotated together with the shaft within the main body, a head unit coupled to both sides of the main body, a guide bearing provided within the head unit, and a mechanical seal configured to block inner gas. A bearing bracket to support the guide bearing is detachably fastened to one side of the head unit by a bolt, and an inner cap and an outer cap are assembled to the inner and outer surfaces of the bearing bracket by fixing bolts.