The friction coefficient of molybdenum disulfide is very low, in the atmosphere is generally 0.03-0.09, the lowest is 0.006-0.03, the highest is 0.15-0.25, is lower than graphite. The friction coefficient in the vacuum is 0.001, the higher is 0.2, namely it has a better lubricating ability in the vacuum. The friction coefficient is reducing with the increasing of temperature and load. It is reducing with the increasing the sliding speed; it may be reduced to less than 0.07. The relative humidity of air also influences the friction coefficient. The friction coefficient is low when the relative humidity is lower than 15%, and reaches the highest point when the relative humidity gets up to 16%.

The molybdenum disulfide is in the shape of hexagonal crystal and in laminated structure. The crystal structure is made up by three plane constitutions: sulfur – molybdenum – sulfur. This kind of structure looks very like “sandwich”. Two sulfur atoms clamp a molybdenum atom in the middle. This thin molybdenum disulfide layer is minimum. Only in the thickness of 0.25 millimeters layer there are approximately 40,000 “pieces”. That is to say the monomer molybdenum disulfide molecule, or the cleft surface (gliding plane), or in 0.001 millimeter layer (namely =1/1000 the millimeter =1 micron), there are 1598 gliding planes, that is in 0.5 micron layer there are 799 gliding planes. This is because in the monomeric molybdenum disulfide molecule the strong covalent bond of sulfur atom and molybdenum atom is hard to separate in the thin layer. And the sulfur atoms between the two monomeric molybdenum disulfide molecules only have the weak van der Waals’ bond (low agglomeration ability), which is easy to separate. Therefore in this extremely thin layer, for example in 0.5 microns layer there are 799 gliding planes. Under so much low shearing force, the low sticky gliding planes change the friction between the original two relative movement objects’ surfaces into the friction between the layers of molybdenum disulfide, thus gets the favorable lubrication effect.

The erosion resistance of the molybdenum disulfide is very strong. Molybdenum disulfide does not react with acid, alkali, and drugs except for nitric, aqua regia, boiling hydrochloric acid, oil of vitriol, pure oxygen, fluorine, chlorine. In PH＞10 alkaline aqueous solution, it has a slow oxygenizement. It is not stable by the influence of strong oxidant and will become molybdenic acid. Molybdenum disulfide is insoluble in cold, hot, boiling water. It is stable in machine oil, fat, petroleum, synthetic lubricant, and in organic solvent such as ethanol, aether: it is stable in ambient gas. In moisture-laden air in room temperature, will have slight oxidize, and will form corrosive acid. After adding molybdenum disulfide to the oil, it is difficult to be oxidized because it cannot fully contact with oxygen in the air, and also the ability of wearing resistance has increased.

Molybdenum disulfide has a good thermal stability. The melting point is 1185 ° C. The air around -184-399℃, its lubricating ability can still be good. The air around 400 °C, it starts to oxidize, 450℃ changes obviously, and 540℃ reaches a violent reaction. The final products are molybdenum trioxide and sulphur dioxide. Before changing into molybdenum trioxide, it keeps lubricating ability. After that, the friction coefficient increases. Mons’ hardness scale of molybdenum trioxide is 2-2.5. The biggest friction coefficient in the air is 0.2. Therefore, most of us think that molybdenum trioxide cannot be used as abrasive material. Naturally, it has been included in the 56 kinds of solid lubricants. Molybdenum dioxide can react on alkali metal including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and Fang (Fr). Application method of molybdenum disulfide in vacuum is different from graphite. It has the good lubricating ability and starts to decompose only when 1093℃. The reason is that the active sulfur atom on the crystal surface of molybdenum disulfide easily has the response with the oxygen in the air. In vacuum when the temperature begins to reach 1093℃, it seems impossible to get rid of the layer of oxygen. Therefore, it has guaranteed the low friction performance even in vacuum because of little cohesion between crystals. Especially under ultrahigh vacuum condition, the friction coefficient reduces instead of elevating to 800℃. Above 800℃, the lubricating ability begins to reduce because of the phase transition of crystal. When in 1093℃, it begins to break down. The lubricating property decreases when puts molybdenum disulfide into the air from vacuum, this is as a result of the absorption of moisture molybdenum disulfide. This is opposite to the graphite, which shows reducing friction coefficient, and increasing lubricating property after the absorption of moisture. Molybdenum disulfide can still lubricate in the low temperature of -184℃ or more lower. When the temperature is less than -200℃, the friction coefficient can hold the line, when is above -200℃, the friction coefficient fold increases.
When in high temperature, molybdenum disulfide can get rid of vapor; this will make the filam on the active facets change into few oxyhydroxide. Because there has hydrogen, it will cause the decrease of tackifying ability of sticky conjunctiva, which formed on the metal surface. So the tackability of molybdenum disulfide to metal surfaces is lower in high temperature than in normal temperature. It is essential to consider the adherence aspect of molybdenum disulfide to metal surfaces when using molybdenum disulfide as lubricant in high temperature. The stronger the adherence is, the better the lubricity is in high temperature.

The compressive property of molybdenum disulfide is very high, other lubricating materials are incomparable in this property. It can still work in the extreme pressure of 20,000 kg/cm2 while the membrane of ordinary lubricant layer will crack, lose lubricity, and cause the heat-sealing of metal surfaces. The result of the test indicated that: If there has molybdenum disulfide between the mental surfaces, and the pressure increases up to 32,000kg/cm2 which is already surpassed the yield stress of some kind of metal, but the surfaces of the two metal will not occlude or fuse. It is tested that molybdenum disulfide in 2.5 microns layer can stand the contact stress of more than 28,000 kg/cm2, and the rubbing speed of 40 meters/second. This high resistance to compression is as a result of its material construction. The pressive strength of graphite is just 200-240000kg/cm2, and is 21,000kg/cm2 of tungsten disulfide.

Molybdenum disulfide has strong adhesion property to metals. Its attachment with metal surfaces is through the surface of sulfur atom and metal. When sulfur and metal combine directly, the combining capacity is so strong that it is difficult to peel off under usual friction. But it is not easy to adhere to unclean surfaces, such as the surfaces, which was tarnished by impurities and oil and so on. On the other hand, the granularity of molybdenum disulfide is very tinny, so it will have larger superficial area. The tinny granularity is easy to fill and level up the uneven places of the metal surfaces. Large surface of the molybdenum disulfide has more opportunities to contact with metal in the form of “sulfur and metal”. When presses, the frictional pyrogenic will make the leptokurtosis of the metal surface flow, so causes the molybdenum disulfide molecule combine with metal, which adhere to the metal surfaces, and form a tinny solid layer of molybdenum disulfide. If the metal surface which molybdenum disulfide contacts is of high degree of finish and is very smooth, and because of the elastic-plastic deformation of the metal, it will form molybdenum disulfide solid thin form when molybdenum disulfide inserts into metal surface. This kind of combination and attachment are relevant to the uneven of the surface of metals, the length of the application of molybdenum disulfide, and the high purity, fine grit of molybdenum disulfide.

The electric conductivity of molybdenum disulfide is not as good as graphite. Its electronic resistivity is 8.51*102 ohm-centimeter, it is poor conductor compared to graphite. In normal temperature or above it, as a mineral, it is better to have the electric conductivity property. In normal condition, it is poor conductor and nonmagnetic material.

Molybdenum disulfide has the property of radio resistance. When in R beam radiation, the friction increases 50% in room temperature. The neutron radiation cannot damage the crystal lattice. Under the radiation condition, it still has the lubrication action. It is tested that: In 7*108 roentgen radiation, molybdenum disulfide and tungsten disulfide have the stable data of kinetic or static friction, while the data of graphite has a big increase. In the aspect of wearing resistance all have varying degree of drop, especially the graphite drops biggest, tungsten disulfide drops smallest, and molybdenum disulfide is next to tungsten disulfide. That is to say that all increase in wearing capacity. The wearing capacity of graphite is 179.9*10-3 cubic millimeter; molybdenum disulfide is 76.2*10-3 cubic millimeter; tungsten disulfide is 66.4*10-3 cubic millimeter.