Molybdenum disulphide (MoS2) is a layered solid lubricant. Unlike graphite it keeps lubricating in dry gas and vacuum, because its layers slide without needing adsorbed moisture. This makes it a standard filler in space, vacuum and dry-gas equipment.
Typical content
Two to five percent by weight on its own, or as a small addition to glass-filled or bronze-filled grades. The common "glass plus MoS2" compound uses about 15 to 20 percent glass and 2 to 5 percent MoS2.
What it improves
- Friction and wear in dry and vacuum service.
- Hardness and compression strength slightly above virgin, so it is less prone to cold flow.
- Nucleation of crystals during cooling, giving a finer structure and a stiffer part.
- Smoother break-in on rough counterfaces.
What it costs you
- Colour and contamination. It is grey-black and can mark parts. Not for food, pharma or clean processes unless specifically allowed.
- Chemistry. Oxidising acids and strong alkalis attack it. Check compatibility, especially in hot service.
- Weaker as a stand-alone strengthener. Because the percent is small, it does not cure creep the way glass or bronze can. It tunes the sliding surface.
- Cost. Higher than glass alone.
Typical applications
Vacuum equipment seals, dry-gas compressors, satellite and aerospace mechanisms, cryogenic valve seats, and bearings running with little or no lubricant.
About the name
You may see names or trade codes for PTFE blends such as glass and MoS2. If a quote refers to a code, ask for the filler type and percent by weight on the certificate. Compound names vary between suppliers, so specify the composition rather than a trade name.
