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Physical & Chemical properties

Vapour pressure

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Description of key information

The vapor pressure for the registered substance was calculated using the US EPA EPI-Suite model because testing was likely to be limited owing to the analytical detection limitations or to the reliability of the test method for this relatively low volatility UVCB material or its components.   
The calculated vapor pressures for the C18-C24 components were as follows:
C18 H38 0.6110 Pa
C20H42 0.1402 to 0.1242 Pa
C22H46 0.0168 Pa
C24H50 0.00313 Pa
Hence, the calculated vapor pressure values for the C18 to C24 hydrogenated components of the registered substance ranged from 0.611 Pa to 0.00313 Pa at 25ºC, indicating low volatility. Overall, the major C20-C22 components (i.e., as much as 95%) of the registered substance have vapor pressure values between 0.1402 and 0.0168 Pa at 25ºC. These findings indicate that the majority of the components in the registered substance is expected to be relatively non volatile.

Key value for chemical safety assessment

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

Additional information

As pointed out in the 2008 ECHA guidance on vapor pressure (Guidance R.7A, pg. 72), the greatest difficulty and uncertainty arise when determining the vapor pressure of chemicals with low volatility, i.e., those with vapor pressures below 1.0 Pa (pascal). The registered substance falls into the area of low volatility owing to its high boiling point, carbon range (C18-C24) and its saturated nature (i.e., no double bond).  For such low volatility materials, vapor pressure testing has limitations owing to uncertainty in measurements for materials in the range of 10-4Pa to 1 Pa (Guidance R.7A, Table R.7.1-15). Also test methods such as the gas saturation method or the vapor pressure balance method can only be applied to pure substances (Guidance R.7A pg 67) and thus may not be suitable or reliable for UVCB substances. Therefore, use of QSPR computational methods to calculate vapor pressure would be considered appropriate and allows for prediction and relative comparision of the range of vapor pressures for the C18-C24 components in the registered material. In the ECHA Guidance R.7A document, the EpiSuite MPBPVP model was discussed as a recommended software for calculating vapor pressure.

In summary, estimated vapor pressure ranges from 0.6110 Pa to 0.00313 Pa at 25 C for the components in the registered substance using the US EPA EPI-Suite v3.12 model. These findings indicate that the majority of the components in the registered substance is expected to be relative non-volatile.

In order to determine vapor pressure of the registered substance, Raoult's law for ideal mimxtures was applied by summing the partial pressures of each constituent >1%.

Constituent Vapor pressure (Pa)
C18 0.611
C20 (8/12 dimer) 0.1242
C20 (10/10 dimer) 0.1402
C22 (10/12 dimer) 0.0168
C24 (12/12 dimer) 0.00313