A practical guide to molybdenum disulfide, why its layered structure makes it a solid lubricant, where it beats graphite and PTFE, and how it is supplied, from a US-based distributor.
Molybdenum disulfide (MoS2, CAS 1317-33-5) is a black-grey solid lubricant that works where oils and greases fail: under extreme load, at high temperature, and in vacuum. Its layered crystal structure shears easily along one plane, which is what produces the low friction. Stratus Chemical supplies technical grade powder across the United States.
| Property | Value |
|---|---|
| Chemical name | Molybdenum disulfide |
| Synonyms | MoS2, moly disulfide, molybdenum sulfide, molybdenite (natural mineral) |
| CAS number | 1317-33-5 |
| Molecular formula | MoS2 |
| Molecular weight | 160.07 g/mol |
| EC / EINECS | 215-263-9 |
| Appearance | Black to lead-grey powder |
| Water solubility | Insoluble |
| Grades supplied | Technical / industrial |
| Packaging | Bags, drums |
| Documentation | COA & SDS provided on request |
The figures below are representative of technical grade molybdenum disulfide. They are intended as a guide and should not be used in preparing a specification: values vary by grade, source, and lot, and the certificate of analysis for your material governs.
| Parameter | Units | Typical value |
|---|---|---|
| MoS2 | % | 98 min |
| Moisture content | % | 0.02 max |
| Specific gravity | g/cc | 4.85 – 5 |
| Melting point | °C | Above 1185 |
| Acid number | mg KOH/g | 0.05 max |
| Acid insoluble | % | 0.5 max |
| Fe | % | 0.25 max |
| C | % | 1.5 max |
| MoO3 | % | 0.05 max |
| Oil content | % | 0.5 max |
Technical grades are produced to a range of specifications. Tell us what your application requires and we will confirm what is available.
Molybdenum disulfide is a layered solid. Each layer is a plane of molybdenum atoms sandwiched between two planes of sulfur, and the bonding within a layer is strong while the bonding between layers is weak. Sliding force makes the layers shear over one another with very little resistance, and the material transfers a thin film onto the surfaces in contact.
That mechanism has nothing to do with a liquid film, which is what makes MoS2 useful where a liquid cannot survive. It carries extremely high contact pressures without being squeezed out, works at temperatures that would degrade an oil, and functions in vacuum where an oil would evaporate. Graphite is often compared to it and works by a related mechanism, but graphite depends on adsorbed water vapour to lubricate and fails in dry or vacuum conditions. MoS2 does not.
The limits are worth knowing too. In air at elevated temperature MoS2 oxidises to molybdenum trioxide, which is abrasive rather than lubricating, so useful service in air is bounded by temperature. The MoO3 line on the certificate is a measure of how much of that oxidation has already occurred in the material as supplied.
The largest use. MoS2 is added to lithium and other greases as an extreme-pressure and anti-seize additive, giving protection at start-up, under shock load, and if the oil film fails entirely. Anti-seize compounds for threaded assemblies rely on it heavily.
Dispersed in a resin binder and applied as a thin film, MoS2 gives a permanent dry lubricant that does not attract dust the way an oil does. Used on fasteners, sliding mechanisms, aerospace components, and anywhere lubrication has to survive without maintenance.
Used in drawing, stamping, forging, and extrusion, where contact pressures exceed what a liquid lubricant can support and the alternative is galling and tool wear.
Compounded into nylon, acetal, and PTFE to lower the friction coefficient and improve wear in bearings, gears, and bushings that run without lubrication.
In vacuum, oils evaporate and graphite stops working. MoS2 performs better in vacuum than in air, which makes it the standard solid lubricant for spacecraft mechanisms and vacuum equipment.
| Solid lubricant | Where it wins | Trade-off |
|---|---|---|
| Molybdenum disulfide | Very high load capacity, works in vacuum and dry conditions, low friction | Oxidises in air at elevated temperature, forming abrasive MoO3 |
| Graphite | Cheap, stable to high temperature in air, widely available | Needs adsorbed moisture to lubricate; fails in dry air and in vacuum |
| PTFE | Lowest friction coefficient, chemically inert, clean and non-staining | Low load capacity and limited temperature range; wears quickly under pressure |
| Tungsten disulfide | Similar layered mechanism with a wider temperature range than MoS2 | Substantially more expensive; usually reserved for demanding applications |
How to choose: match the lubricant to the failure mode. If the problem is load — galling, seizing, or an oil film that collapses under pressure — MoS2 is the standard answer. If the environment is hot and oxidising and load is moderate, graphite holds up better. If friction needs to be as low as possible and loads are light, PTFE wins. In vacuum or dry conditions, graphite is out and MoS2 is in. Many commercial products blend two of these rather than relying on one.
Store molybdenum disulfide dry in closed original packaging, off damp floors. The material is stable and does not degrade under normal storage, but moisture pickup promotes slow oxidation and causes caking of fine powder.
Keep it away from strong oxidising agents and from prolonged heat in air. The oxidation product, molybdenum trioxide, is abrasive rather than lubricating, so material that has been stored hot may not perform as expected.
The main handling issue is dust. MoS2 powder is fine, dark, and gets everywhere, and it stains surfaces persistently. Use the ventilation and respiratory protection specified in the Safety Data Sheet, avoid dry sweeping, and expect spills to need proper cleaning rather than a brush.
Molybdenum disulfide is used as a solid lubricant. Its largest use is as an extreme-pressure additive in greases and anti-seize compounds, followed by bonded dry film coatings on fasteners and sliding mechanisms, metal forming operations such as drawing and forging, self-lubricating plastics and composites, and vacuum and aerospace mechanisms where oils cannot survive. Stratus Chemical supplies technical grade powder across the United States.
The CAS number for molybdenum disulfide is 1317-33-5. Its molecular formula is MoS2 and its molecular weight is 160.07 g/mol. Its EC number is 215-263-9. It is also known as moly disulfide, molybdenum sulfide, and in its natural mineral form as molybdenite.
Because of its layered crystal structure. Each layer is a plane of molybdenum atoms between two planes of sulfur, with strong bonding inside a layer and weak bonding between layers. Sliding force shears the layers over one another with very little resistance, and the material transfers a thin lubricating film onto the contacting surfaces. Because this does not depend on a liquid film, it survives contact pressures that would squeeze out an oil.
Both are layered solids that shear easily, but graphite depends on adsorbed water vapour between its layers to lubricate, so it loses effectiveness in dry air and fails in vacuum. Molybdenum disulfide does not need moisture and actually performs better in vacuum than in air, which is why it is the standard choice for space and vacuum mechanisms. Graphite, in exchange, is cheaper and more stable at high temperature in air, where MoS2 oxidises.
Store it dry in closed original packaging, off damp floors and away from strong oxidising agents and prolonged heat in air. The material is stable, but moisture promotes slow oxidation to molybdenum trioxide, which is abrasive rather than lubricating, and causes fine powder to cake. The practical handling issue is dust: it is fine, dark, stains persistently, and needs the ventilation and respiratory protection specified in the Safety Data Sheet.
Stratus Chemical supplies molybdenum disulfide in bags and drums, in technical grade powder, with a certificate of analysis provided for each shipment. Tell us the grade, purity, and volume you need and we will confirm pricing and availability within one business day.
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