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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
07/05/2010 – 10/08/2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
yes
Remarks:
OECD proposes a temperature range of 0 – 50 °C or 120 – 150 °C. This range was ex-tended in the experimental run as several test items were examined simultaneously, and other test items showed much higher vapour pressures.
GLP compliance:
yes (incl. certificate)
Type of method:
effusion method: by loss of weight or by trapping vaporisate
Temp.:
25 °C
Vapour pressure:
0.013 Pa
Temp.:
20 °C
Vapour pressure:
0.009 Pa

The vapour pressure of 4,4'-MDI/DPG was determined following EU A.4 by the effusion method (weight loss).

Vapour pressure at 12 different temperatures was examined. Three temperatures could be evaluated as they showed reproducible weight loss. For these temperatures, 1/T was plot-ted against log (P).

Table: Vapour Pressures (Effusion Method)

Experiment

 T  P  Stand. Dev. P  RSD P
 No.  K  Pa  Pa  %
 4  321.5  5.91E-02 1.12E-02 19.0% 
 5 335.3   1.43E-01  1.32E-02  9.2%
 6 349.2  2.72E-01  1.39E-01  51.0%

In this table, E-02 represents * 10-2 , resp. E-01 represents * 10-1.

The graph 1/T vs. log (P) shows a straight line with a correlation coefficient of -0.9976.

For the test item 4,4'-MDI/DPG, the following estimated vapour pressures at 20°C and at 25°C were calculated from the regression equation:

Vapour pressure at 20°C: 9.42 * 10-03 Pa

Vapour pressure at 25°C: 1.34 * 10-02 Pa

Conclusions:
The following estimated vapour pressures at 20°C and at 25°C were calculated from the regression equation:
Vapour pressure at 20°C: 9.42 * 10-03 Pa
Vapour pressure at 25°C: 1.34 * 10-02 Pa

Description of key information

The experimental method used at Chilworth Technology Ltd. for vapour pressure determination was not suitable and the recommended ranges were inappropriate. Therefore, the study from Chilworth Technology Ltd., is considered to be Klimisch 2 reliability rating and it must be ignored.  
The following estimated vapour pressures at 20°C and at 25°C were calculated from the regression equation:
Vapour pressure at 20°C: 9.42 * 10E-03 Pa
Vapour pressure at 25°C: 1.34 * 10E-02 Pa

Key value for chemical safety assessment

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

Additional information

Two studies are available on determination of vapour pressure of MDI/DPG. In the initial study, the experimental method used at Chilworth Technology Ltd. for the test substance, vapour pressure determination was not considered suitable and the recommended range of 10E+2 to 10E+5 Pa was inappropriate for MDI/DPG.

Therefore, while the report from Chilworth Technology Ltd., (Report no. GLP102942ER1V1/09), is considered to be Klimisch 2 reliability rating it must be ignored. The second study carried out at LAUS with the suitable method for this type of substance and the following vapour pressures are achieved:

Vapour pressure at 20°C:  9.42 * 10E-03 Pa        

Vapour pressure at 25°C:  1.34 * 10E-02 Pa