Registration Dossier

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 27.6 hPa at 20°C for the substance as placed on the market.

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, 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.

Categories Display