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Physical & Chemical properties

Vapour pressure

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Description of key information

Vapour pressure [whole substance]: 124 Pa at 20°C and 161 Pa at 25°C (OECD 104)

Vapour pressure [(trimethoxysilylpropyl)methylmethylphosphonate]: 0.077 Pa at 25°C (QSAR)

Vapour pressure [bis(trimethoxysilylpropyl)methylphosphonate]: 2.5E-04 Pa at 25°C (QSAR)

Vapour pressure [(trihydroxysilylpropyl)methylmethylphosphonate]: 1.2E-06 Pa at 25°C (QSAR)

Vapour pressure [bis(trihydroxysilylpropyl)methylphosphonate]: 1.1E-09 Pa at 25°C (QSAR)

Vapour pressure [methanol]: 12790 Pa at 20°C

Key value for chemical safety assessment

Vapour pressure:
124 Pa
at the temperature of:
20 °C

Additional information

Vapour pressure values of 124 Pa at 20°C and 161 Pa at 25°C were determined for the substance using a static method in accordance with OECD Test Guideline 104 and in compliance with GLP. The result is considered to be reliable.

The submission substance is a multi-constituent substance containing two constituents. The measured vapour pressure for the whole substance is preferred for the purposes of human health assessment while for the purposes of environmental hazard and fate assessment, the vapour pressures of the constituents have been obtained using relevant QSAR estimation method. Predicted vapour pressure values of 0.077 Pa at 25°C and 2.5E-04 Pa at 25°C were determined for Constituent 1 and Constituent 2 respectively.

In contact with water, the constituents of the submission substance hydrolyse rapidly forming (trihydroxysilylpropyl)methylmethylphosphonate (HP 1) and bis(trihydroxysilylpropyl)methylphosphonate (HP 2) as the silanol hydrolysis products for Constituent 1 and Constituent 2 respectively. The other hydrolysis product for both constituents is methanol.

The vapour pressure of the silanol hydrolysis products have been predicted using the same QSAR estimation method and the parent constituents. Predicted vapour pressure values of 1.2E-06 Pa at 25°C and 1.1E-09 Pa at 25°C were obtained for HP 1 and HP 2 respectively.

Methanol has a reported vapour pressure of 12790 Pa at 20°C (OECD 2004).

Reference:

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