Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Endpoint summary

Administrative data

Description of key information

Additional information

Hexamethyldisiloxane is a liquid at standard temperature and pressure, with a measured melting point of -68.2°C, and a measured boiling point of 100.5°C. It has a measured density of 0.76 g/cm3 at 20°C and moderate kinematic viscosity of 0.65 mm2/s at 25°C. It is highly volatile with a measured vapour pressure of 5500 Pa at 25°C.

The substance is classified as highly flammable on the basis of a measured flash point of -6°C and boiling point of 100.5°C. It has an auto-ignition temperature of 340°C, is not explosive and is not oxidising on the basis of structural examination.

In contact with water, hexamethyldisiloxane reacts slowly, half-life of 116 h (5 days) at pH 7 and 24.8°C according to the following equation:

(CH3)3SiOSi(CH3)3+ H2O → 2(CH3)3SiOH 

Hexamethyldisiloxane is slightly soluble in water (water solubility of 0.93 mg/l at 23°C) and has a measured log Kow of 5.06 at 20°C. It does not dissociate in solution nor show significant surface activity.