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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane is a liquid substance at room temperature with a melting point of <20°C. The substance has a measured boiling point of >400°C (and a predicted boiling point of 530°C) and a predicted density of 1.1 g/cm3 at 20°C and a predicted vapour pressure of 1.3E-08 Pa at 25°C.


The substance is not classified for flammability in accordance with Regulation (EC) No. 1272/2008 on the basis of a measured flash point of 266°C and measured boiling point of >400°C. It has a measured auto-flammability temperature of 483±3°C, and is not explosive and not oxidising on the basis of structural examination.


1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane has a predicted log Kow of 9 and predicted water solubility of 8.5E-11 mg/l at 20-25°C.

In contact with water, 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane is expected to react slowly (half-lives of 329 h (13.7 d) at pH 7, 9.76 h at pH 9, and 5.09 h at pH 5 and 25°C are read-across from a structurally similar substance). The half-lives described are for the removal of parent substance. The intermediate products of this reaction are also expected to be unstable in water, and so further hydrolysis reactions will follow, the ultimate products being methyl(phenyl)silanediol (1 mole per mole of parent substance) and methyl(diphenyl)silanol (2 moles per mole of parent substance).