Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Dodecamethylpentasiloxane (L5) is a liquid at ambient temperature and pressure, with a measured melting point of -80°C and a boiling point of 210 - 232°C. It has a density of 0.88 - 0.94 g/cm3 at 20°C, a kinematic viscosity of 1.7 mm2/s at 20°C and a predicted vapour pressure of 7.8 Pa at 25°C.

The substance is not classified for flammability on the basis of a measured flash point of 79°C and boiling point of 210 - 232°C. It has a measured auto-ignition temperature of 350°C, and is not explosive and not oxidising on the basis of structural examination.

In contact with water, L5 reacts slowly, half-lives of 14 hours at pH 5, 30.3 days (728 hours) at pH 7 and 21.1 hours at pH 9 and 25°C. The stated half-life is for removal of parent substance. Complete reaction to the ultimate end products will take longer. The reaction equation is shown below:

(CH3)3SiO[Si(CH3)2O]3Si(CH3)3 + 4H2O → 2(CH3)3SiOH + 3(CH3)2Si(OH)2

The substance has a measured water solubility of 0.00007 mg/l at 23°C and a measured log Kow of 9.4 at 25°C. The substance is not surface active based on examination of the chemical structure.