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Physical & Chemical properties

Endpoint summary

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Dimethylbis(octadecyloxy)silane is a low melting-point solid at standard temperature and pressure, with a melting point of 32°C and a measured boiling point of 407°C. It has a measured relative density of 0.889 at 20°C and measured vapour pressure values of 4E-04 Pa at 20°C and 0.023 Pa at 50°C.

The substance is not classified for flammability according to Regulation EC (No.) 1272/2008 on the basis of a measured flash point of 199.5°C and a boiling point of 407°C. It has a measured auto-ignition temperature of 353°C at 963 -969 hPa, and is not explosive and not oxidising on the basis of chemical structure.


Dimethylbis(octadecyloxy)silane reacts with water (predicted half-life of >15 hours) to form dimethylsilanediol (1 mole) and 1-octadecanol (2 moles) according to the following equation:


 (CH3)2Si(O(CH2)17CH3)2+ 2H2O → (CH3)2Si(OH)+ 2CH3(CH2)16CH2OH


Dimethylbis(octadecyloxy)silane has a predicted water solubility of 2.5E-14 mg/l at 20-25°C, and a predicted log Kow of 9.0 at 25°C. Given the very high adsorption potential and very low water solubility hydrolysis is likely to be very slow in the environment and in vivo.