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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Octaphenylcyclotetrasiloxane is a solid substance at ambient temperature and pressure, with a melting point of >200°C and a predicted boiling point of 730°C at 1013 hPa. It has a relative density of 1.185 at 20°C and a predicted vapour pressure of <1E-06 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 flammability of solids study in accordance with UN N.1 Test Method and a Combustion Class study according to the principles of VDI2260 Part 1.

No self-ignition temperature of the test item was observed up to the melting point at about 200°C. It is not explosive and not oxidising on the basis of structural examination.

A hydrolysis study was not conducted for the substance due to very low solubility in water. Cyclic siloxanes such as octaphenylcyclotetrasiloxane can undergo hydrolysis reactions in water, resulting in breaking of the Si-O bonds. The first step is ring-opening to give a linear siloxanediol (octaphenyltetrasiloxanediol for the present substance). This intermediate then undergoes chain-shortening reactions to give the final silanediol product.The expected equation for the hydrolysis reaction is shown below:


[-Si(C6H5)2O-]4+ 4H2O → 4(C6H5)2Si(OH)2


The final product is diphenylsilanediol.

However, due to the extremely low water solubility of the substance, hydrolysis is not expected to be a significant removal process.

Octaphenylcyclotetrasiloxane has a predicted log Kow of 9.0 at 20°C and a predicted water solubility of <1E-05 mg/l at 20°C. The substance is not surface active based on structural examination. Median particles size in the range of 125 - 250 µm was determined for the substance as such.

Additional information