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Physical & Chemical properties

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Tris(isopropenyloxy)(vinyl)silane is a liquid at standard temperature and pressure, with a measured melting point of <-80°C and a predicted boiling point of 220°C. It has a predicted density of 0.9 g/cm3 at 20°C and a predicted vapour pressure of 5.3 Pa at 25°C.

The substance is not classified for flammability according to Regulation (EC) No 1272/2008 on the basis of a measured flash point of 71.5°C and a predicted boiling point of 220°C. It has a measured auto-ignition temperature of 265°C, and it is not explosive and not oxidising on the basis of chemical structure.

In contact with water tris(isopropenyloxy)(vinyl)silane reacts rapidly (half-life of ≤0.3 hours at pH 4, ≤0.4 hours at pH 5, ≤6.6 hours at pH 7 and ≤0.1 hours at pH 9 and 20-25°C) to produce vinylsilanetriol and propen-2-ol according to the following equation:

C11H18SiO3 + 3H2O → C2H6SiO+ 3C3H6O

 

Therefore, requirements for testing of water-based physicochemical properties for the substance are waived on the basis of instability in water. The properties of the silanol hydrolysis product, vinylsilanetriol, are assessed instead. However, the key physicochemical properties of the submission substance have been predicted using validated QSAR estimation methods. Tris(isopropenyloxy)(vinyl)silane has a predicted water solubility value of 130 mg/l at 20°C and a predicted log Kow value of 3.8 at 20°C.

The hydrolysis of [tris(isopropenyloxy)(vinyl)silane] produces vinylsilanetriol and 3 molecules of propen-2-ol. Propen-2-ol is an enol type structure, which is in equilibrium with its keto tautomer, propanone (commonly called acetone). The equilibrium heavily favours the keto form at room temperature. Therefore, the properties of acetone as well as vinylsilanetriol are considered for the chemical safety assessment. Acetone is miscible with water, has low log Kow (-0.24) and high vapour pressure values of approximately 24300 Pa at 20°C and 53330 Pa at 39.5°C (12790 Pa at 20°C) (OECD 1999).

 

The saturation concentration in water of the silanol hydrolysis product, vinylsilanetriol is limited by condensation reactions that can occur over time at loadings above approximately 1000 mg/l. However, it is very hydrophilic (calculated solubility is 1.0E+06 mg/l at 20°C using a QSAR method) and has a low log Kow (-2.0, predicted).

The silanol hydrolysis product is not expected to be surface active and it is much less volatile than the parent substance (vapour pressure = 0.017 Pa at 25°C, predicted).

Reference:

OECD (1999): SIDS Initial Assessment Report (SIAR) for the 9th SIAM, Paris, France, 29 -30 June 1999, Acetone, CAS 67-64-1.