Molybdenum sulfide

Flammability

Link to relevant study record(s)

Reference

Endpoint:

flammable solids

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.10 (Flammability (Solids))

GLP compliance:

yes (incl. QA statement)

Remarks:

2009-10-29

Test procedure:

burning rate test: preliminary screening test

Remarks on result:

substance does not ignite and propagate combustion either by burning with flame or smouldering along 200 mm of the powder train within the 2 minutes test period

The test item could not be ignited with a flame in the pre-test. The test item remained unchanged at contact with the flame. A main test was not necessary.

Interpretation of results:

not classified based on GHS criteria

Conclusions:

Molybdenum disulfide could not be ignited with a flame in the pre-test, therefore it was not classified based on GHS criteria.

Description of key information

MoS₂ is neither pyrophoric, nor flammable in contact with a flame and MoS₂ does not develop flammable gases in contact with water (also refer to justification to classification or non-classification).

Key value for chemical safety assessment

Flammability:

not classified

Justification for classification or non-classification

MoS₂ is not pyrophoric, i.e. it does not react spontaneously or violently with air at ambient temperatures. MoS₂ is practically insoluble in water and does not react with water under the formation of flammable gas. The reaction/oxidation behaviour of MoS₂ has also been studied extensively by researchers (see Risdon, 2003 and references therein). Whereas MoS₂ oxidises to MoO₃ and whereas this reaction is exothermic, it requires a high activation energy and only takes place at a measurable rate above 300 °C.

In an experimental study on the flammability of solids (EU A.10 method), molybdenum disulfide could not be ignited with a flame (Smeykal, 2010). In an experimental study according to method EU A.16, the relative self-ignition temperature of a sample of MoS₂ has been determined at 312 °C (Henke, 2012). The self-ignition temperature is not a definitive value for a substance, as it is a function of several variables, such as particle size, way of confinement and sample amount. Self-ignition of MoS₂ does not occur under normal ambient conditions of handling, storage, transport or use. In Industry the oxidation of MoS₂ is used to produce technical MoO₃ from molybdenite ore (MoS₂). This technical process takes place under controlled conditions in large multiple hearth furnaces at ca. 500 - 600 °C, to achieve complete oxidation.

Thus, based on the well understood reaction characteristics of MoS₂ and on long-term industrial experience, MoS2 does not require hazard classification as a flammable solid.