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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Flammability

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Endpoint:
flammable liquids: obsolete as covered by section 'Flash point'
Data waiving:
study technically not feasible
Justification for data waiving:
the study does not need to be conducted because the substance is a liquid
Endpoint:
substances / mixtures which in contact with water emit flammable gases
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
Endpoint:
pyrophoric liquids
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is known to be stable in contact with air at room temperature for prolonged periods of time (days) and hence, the classification procedure does not need to be applied

Description of key information

The substance, 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3; EC No. 213-668-5):

•       Is flammable (based on a measured flash point of 11.4°C and a boiling point 125°C)

•       In contact with water does not emits a flammable gas

•       Is not pyrophoric

Key value for chemical safety assessment

Flammability:
flammable

Additional information

The flammability study is not required for liquids as flammability is assessed on the basis of the flash point.

There is no indication on the basis of chemical structure and experience in handling and use that the substance is pyrophoric (flammable in contact with air) or flammable in contact with water.

Therefore, in accordance with Section 1 of REACH Annex XI, there is no need to conduct further flammability testing.

A Lower Explosion Limit of 0.69 (vol%) and an Upper Explosion Limit of 23.2 (vol%) at 100°C and 5.3 L test chamber were obtained for the substance using ASTM E681-94 (Dow Corning Corporation 1998). In a second study (Southwest Research Institute 2000), a Lower Explosion Limit of 0.3% and an Upper Explosion Limit of 41% were determined for the substance using a relevant test method.

In a secondary source to which reliability could not be assigned, Lower Explosion Limit of 0.8% and Upper Explosion Limit of 25.9% were reported for the substance.

Justification for classification or non-classification

Flammable liquid:

The substance is classified as Flammable Liquid Category 2 (H225: Highly Flammable liquid and vapour) according to Regulation (EC) No. 1272/2008. This is on the basis of a measured flash point value of 11.4°C at 1013 hPa and a boiling point of 125°C at 1013 hPa.

Flammability in contact with air:

There is no indication to classify the substance for this hazard on the basis of Regulation (EC) No. 1272/2008.

Flammability in contact with water:

There is no indication to classify the substance for this hazard on the basis of Regulation (EC) No. 1272/2008.