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Physical & Chemical properties

Vapour pressure

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Description of key information

For the volatilisation the partial pressure of the hydrolysis products (formaldehyde, ethylene glycol) should be used (< 13 Pa).

Key value for chemical safety assessment

Vapour pressure:
13 Pa
at the temperature of:
25 °C

Additional information

EUF is a complex reaction mixture (UVCB substance) consisting of several constituents, and thus the vapour pressure of the mixture is defined by the partial pressure of the single constituents. Identified constituents of EUF are different methylolated ethylene glycols (e.g., monomethylol ethylene glycol, dimethylol ethylene glycol, trimethylol ethylene glycol, etc.), urea derivatives and the reactants ethylene glycol and formaldehyde.

The vapour pressure of the complex reaction mixture has been experimentally determined to be 500 Pa at 20 °C and 730 Pa at 25 °C according to the EC method A.4 and OECD 104. However, these values are probably only caused by the partial pressure of that single constituent, which has the highest partial pressure.

Therefore, the vapour pressure above EUF has been deduced for the identified single constituents and proposed constituents using a generally accepted calculation method (ITEM 2008). The vapour pressure of several constituents was calculated to be in the range between 2.21·10E-6 Pa and 8.6 Pa at 25°C. The partial pressure of the hydrolysis products formaldehyde, ethylene glycol and urea has been given to be < 13 Pa. This range is considered to be more realistic than the measured value (730 Pa at 25°C), where probably water had been determined in the gas phase.

The partial pressure of formaldehyde under realistic conditions had been calculated based on the measured values to be <10 Pa for concentrations of 10 – 100% (ITEM, 2010). At lower concentrations the partial pressure will decrease. As a worst-case the 5 Pa could be used for 1% solutions, too. As further hydrolysis at lower concentrations is very slowly and more than 50% of the releasable formaldehyde is available, the partial pressure above a 0.15% solution could be extrapolated using Raoult`s law (ca. 0.75 Pa).

Overall, the partial pressure of the hydrolysis products should be used for the volatilisation (< 13 Pa).