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Physical & Chemical properties

Water solubility

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Description of key information

Water solubility [(1,1,3,3-tetramethyldisiloxane-1,3-diyl)dipropane-1,3-diyl dimethacrylate]: 1.5E-03 mg/L at 20°C (QSAR)

Water solubility [3-[hydroxy(dimethyl)silyl]propyl methacrylate]: can undergo condensation reactions in water to some extent, limiting the concentration in water (estimated threshold approximately 30 mg/l, but could be much less than this, depending on the conditions). The calculated water solubility is 330 mg/L at 20°C (QSAR). The condensation reaction re-generates the parent substance.

Key value for chemical safety assessment

Water solubility:
0.002 mg/L
at the temperature of:
20 °C

Additional information

The water solubility of the parent substance has been predicted to be 1.5E-03 mg/L at 20°C using a validated QSAR estimation method. The result is considered to be reliable.

In contact with water, the substance hydrolyses slowly to form 3-[hydroxy(dimethyl)silyl]propyl methacrylate.

The silanol hydrolysis product, 3-[hydroxy(dimethyl)silyl]propyl methacrylate may undergo condensation reactions in solution to give the siloxane dimer and a dynamic equilibrium is established .The overall rate of condensation is dependent on nominal loading, temperature, and pH of the system, as well as what else is present in the solution. It may also change over time.

The condensation reactions of monosilanols may be modelled as an equilibrium between monomer and dimer. The reaction is reversible unless the dimer concentration exceeds its solubility; in this case, the dimer forms a separate phase, driving the equilibrium towards the dimer. For 3-[hydroxy(dimethyl)silyl]propyl methacrylate, at loadings above about 30 mg/L the concentration of the dimer is predicted to exceed its solubility, resulting in formation of a separate phase. In addition, the dimer is expected to have a high volatility from water and this may cause losses from water under some conditions. Further information is given in a supporting report (PFA 2016am) attached in Section 13.

The water solubility of the silanol hydrolysis product, 3-[hydroxy(dimethyl)silyl]propyl methacrylate has been calculated using a validated QSAR method to be 330 mg/L. However, the saturation concentration may in reality be limited by the formation of less soluble dimer rather than the solubility of the monomer itself.

Reference:

PFA, 2016am, Peter Fisk Associates, Silanols and aquatic systems, 404.105.003