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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

1,1,5,5,5-Hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (M4Q) is a liquid at standard temperature and pressure, with a measured melting point of <-50°C and a measured boiling point of 229.8°C. It has a relative density of 0.877 at 20°C. The substance has a measured vapour pressure values of 15 Pa at 25°C.

The substance is not classified for flammability according to Regulation (EC) No. 1272/2008 on the basis of a measured flash point of 85.0°C and a measured boiling point of 229.8°C. It has a measured auto-ignition temperature of 345°C and is not explosive and not oxidising on the basis of structural examination.

No hydrolysis study is available for M4Q. Hydrolysis half-life values of 6.6 h at pH 4, >200-2000 h at pH 7, 13.9 h at pH 9 and 20-25°C were obtained using an accepted calculation method. Under laboratory conditions, the final hydrolysis products of M4Q are monosilicic acid Si(OH)4 and trimethylsilanol (Me3SiOH). Monosilicic acid exists only in dilute aqueous solutions and readily condenses at concentrations above ca. 100 - 150 mg/l as SiO2 to give a dynamic equilibrium between monomer, oligomers and insoluble polysilicic acid.

The properties of the parent substance are assessed as hydrolysis in water is slow. The substance has a predicted log Kowof 9.0 at 20°C and a measured water solubility of 0.1507 µg/l at 23°C.