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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:
June 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well conducted study, according to ASTM E1782-08 . This method is not included into EC Regulation No 761/2009, Guideline A.4, but it is expected that this will occur in the near future. Composition of substance with GC analysis incuded in the report.
Qualifier:
equivalent or similar to
Guideline:
EU Method A.4 (Vapour Pressure)
Version / remarks:
July 23, 2009
Deviations:
not applicable
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
Adopted march 23, 2006
Deviations:
not applicable
Qualifier:
according to
Guideline:
other: ASTM E1782-08,Standard test method for determining vapour pressure by Thermal Analysis, March 1, 2008
Deviations:
no
Principles of method if other than guideline:
This ASTM method was taken, because for substances which are thermally unstable and contain impurities it is a more suitable method than the other methods listed in the above-mentioned guidelines. It is expected that this method will be included into EC Guideline A.4 in the near future. Last year a request for inclusion was sent to the Dutch National Coordinator for EC Test Methods.
GLP compliance:
no
Type of method:
other: DSC, Differential Scanning Calorimetry
Temp.:
20 °C
Vapour pressure:
0.002 Pa
Remarks on result:
other: The vapour pressure of pure 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane may be slightly higher than 1.75.10-6 kPa at 20°C, but it certainly will not be higher than 0.01 Pa.

Calibration

The pressure transducer was calibrated at June 4, 2010 over a pressure range of 0 to 13 kPa. The measured deviation was maximum 0.0013 kPa.

The temperature deviation as function of pressure was determined over a pressure range of 0.02 – 100 kPa with 12.74 mg Indium in a70 µl Aluminium cup with pierced lid. The heating rate was 5°C/min. The measured boiling temperatures of the test substance at the different pressures were corrected for this deviation.

 

Test substance

Five measurements at different pressures were carried out with the test substance. The intakes, the measured boiling temperatures and their corresponding observed pressures are listed in the table below.

 

Measurement

Intake

[mg]

Observed pressure

[kPa]

Boiling temperature

[°C]

1

15.04

0.0395

58.35

2

14.95

0.0839

65.24

3

15.12

0.1180

70.33

4

14.78

0.2500

82.08

5

14.75

0.5180

94.36

 

The p,T-diagram of the individual measurements is shown in the attachment with the Antoine fit (regression line) of the measured data.

The Antoine equation constants A, B and C are calculated from this fit. This results in the following Antoine equation:

Log p (kPa) = 1.701918 – {203.4461/[ T(K) – 265.875]}

           

 

The estimated vapour pressure of the test substance calculated from this equation is 1.75∙10-6kPa at 20°C

 

The impurities in the test substance will have vapour pressures equal to or lower than that ofDi-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide, since the more volatile impurities were removed during the sample preparation step. This means that the vapour pressure of pure

Di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxidemay be slightly higher than the measured value of1.75∙10-6kPa at 20°C. But because of the low amount of remaining impurities, it certainly will not be higher than the cut off value of 0.01 Pa (i.e.10-5kPa), which is applied in the ECETOC Targeted Data Risk Assessment Report (see below).

 

  1.75.10-6 kPa= 0.00175Pa

 

 

 

 

 

Conclusions:
The estimated vapour pressure of the test substance is 1.75.10-6 kPa at 20°C.

The vapour pressure of pure Di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide may be slightly higher than 1.75.10-6 kPa at 20°C, but it certainly will not be higher than 0.01 Pa.
Executive summary:

This study is done with a purified di-tert-butyl 1,1,4,4-tetramethylene diperoxide, so with a minimum interference of volatile impurities, which enhance the vapour pressure..

The vapour pressure of pure di-tert-butyl 1,1,4,4-tetramethylene diperoxide may be slightly higher than 0.00175 Pa at 20°C, but it certainly will not be higher than 0.01 Pa.

Description of key information

The estimated vapour pressure of the test substance is 1.75.10-6 kPa at 20°C.

The vapour pressure of pure Di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide may be slightly higher than 1.75.10-6 kPa at 20°C, but it certainly will not be higher than 0.01 Pa.

Key value for chemical safety assessment

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

Additional information

Two studies are available on the vapour pressure determination of the product Trigonox 101.The first study (Nagelhout, 2011) shows an extrapolated vapour pressure of 0.00175 Pa at 20°C. This value is used as key value for chemical safety assessment.

In the second disregarded study, the vapour pressure was found to be 3.8 mbar at 90 °C and 24 mbar at 123 °C. Using the Antoine equation, the calculated vapour pressure at 25 °C is 0.016 mbar.