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Physical & Chemical properties

Endpoint summary

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Description of key information

3-Trimethoxysilylpropyl methacrylate is a liquid at standard temperature and pressure, with a measured melting point of <-20°C and a measured boiling point of 253°C at 1017 hPa. It has a density of 1.04 g/cm3at 20-25°C, a predicted kinematic viscosity of 3.2 mm2/s at 20°C and a measured vapour pressure of 2.3 Pa at 25°C.

The substance is not classified for flammability according to Regulation (EC) No. 1272/2008 on the basis of a flash point of 100-110°C and a measured boiling point of 253°C at 1017 hPa. It has a measured auto-ignition temperature of 275°C at 1017.5 -1030.7 hPa and is not explosive and not oxidising on the basis of chemical structure.

The reliability of the reported data for density and flash point cannot be assigned. Therefore, further testing is planned for these endpoints.

In contact with water, 3-trimethoxysilylpropyl methacrylate reacts rapidly (half-life of 0.018 h at pH 4, 1.87 h at pH 7, and 0.068 h at pH 9 and 20°C) to produce 3-(trihydroxysilyl)propyl methacrylate and methanol according to the following equation:

H2C=C(CH3)C(=O)O(CH2)3Si(OCH3)3+ 3H2O ¿ H2C=C(CH3)CO2(CH2)3Si(OH)+ 3CH3OH


Therefore, requirements for testing of water-based physicochemical properties for the substance are waived on the basis of instability in water. However, the parent substance has a measured log Kow of 2.1 and a predicted water solubility of 2200 mg/L at 20°C.

The properties of the hydrolysis products, 3-(trihydroxysilyl)propyl methacrylate and methanol are assessed instead.

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 2004a).


The saturation concentration in water of the silanol hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate is limited by condensation reactions to approximately 1000 mg/L. However, it is very hydrophilic (calculated solubility is 1E+06 mg/L using a QSAR method) with a predicted low log Kow value of -0.9. It is not surface active and does not undergo significant dissociation within the environmentally-relevant range. It is much less volatile than the parent substance with a predicted vapour pressure of 1.2E-05 Pa at 25°C. The first dissociation constant of a structurally analogous silanetriol (phenylsilanetriol) has been reported to be around pKa= 10.



OECD (2004a): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.


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