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3-(Trimethoxysilyl)propyl-(2E,4E)-hexa-2,4-dienoate is a liquid at standard temperature and pressure, with a measured melting point of <-20°C, it undergoes decomposition without boiling from about 295°C. It has a measured density of 1.04 g/cm3 at 25°C, a measured kinematic viscosity of 6.4±0.3 mm2/s at 25°C and a predicted vapour pressure of 0.052 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 146±2°C. Under the conditions of an EU Test Method A.12, the substance is not classified for flammability in contact with water. It has a measured auto-ignition temperature of 290°C at 749 -752 mmHg (99858.45 - 100258.42 Pa), and is not explosive and not oxidising on the basis of examination of the chemical structure.

In contact with water, 3-(trimethoxysilyl)propyl-(2E,4E)-hexa-2,4-dienoate reacts rapidly (half-life 4.7 hours at pH 7, 9.6 minutes at pH 5, 6 minutes at pH 9 and 25°C) to produce 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate and methanol according to the following equation:

(CH3O)3Si(CH2)3O(C=O)CH=CHCH=CHCH3+ 3H2O → (OH)3Si(CH2)3O(C=O)CH=CHCH=CHCH3+ 3CH3OH

It has a measured log Kow value of 3.09 at 30°C and measured water solubility value of 442 mg/l at 20°C.

Methanol is miscible with water, has low log Kow (-0.82 to -0.64) and high vapour pressure (12,790 Pa at 20°C) (OECD 2004).

The saturation concentration in water of the silanol hydrolysis product, 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate 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 (-0.3, predicted). It is less volatile than the parent substance (vapour pressure of <1.0E-03 Pa at 25°C, predicted).

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