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Melting point / freezing point

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Reference
Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
20-02-2018 to 26-07-2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Guideline study performed under GLP. All relevant validity criteria were met.
Qualifier:
according to guideline
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7200 (Melting Point / Melting Range)
Deviations:
no
GLP compliance:
yes
Type of method:
differential scanning calorimetry
Melting / freezing pt.:
>= -53.8 - <= -49.2 °C
Atm. press.:
ca. 1 013 hPa
Decomposition:
no
Remarks:
No decomposition during Melting Point determination
Sublimation:
no
Remarks on result:
other: melting point range (glass transition) ; n = 3; measurement under flow of nitrogen

Main study

- Experiment 1: During cooling, a glass transition between -40°C and -80°C was found. During heating a glass transition was observed between -75°C and -25°C followed by an exothermic effect starting at ca. 75°C. The inflection point of the glass transition was -49.179°C.

- Experiment 2: A duplicate DSC was performed to further investigate the glass transition of the test item. Similar results as in Experiment 1 were obtained. The inflection point of the glass transition peak was -53.791°C. After the experiment it was observed that the test item was unchanged. As difference in the inflection point between Experiment 1 and Experiment 2 was > 0.5°C, Experiment 3 was performed.

- Experiment 3: Using conditions similar to Experiment 2, the inflection point of the glass transition was -53.442°C. Since result of the Experiment 3 was in line with the inflection points observed in Experiment 1 and Experiment 2, results were accepted.

 

The mean glass transition temperature (n = 3) was -52.1°C.

 

Applicant assessment of the DSC curve indicates: the substance appears to have constituents that possess amorphous solid properties at low temperatures (< 20 °C) and possesses a Glass Transition Temperature (Tg) analogous to the conventional ‘melting point’ as defined under the OECD TG 102 guideline. This is a temperature point where the substance possesses glass form as opposed to possessing super-cooled liquid form. For hazard assessment the substance should be treated as a liquid. This is based on the bulk properties of the test item being clearly ‘liquid’ as defined in Regulation (EC) 1272/2008: Annex I, section 1.0. In that the substance is not gaseous and has a vapour pressure < 300 kPa at 50°C and/or has an ‘initial melting point’ at < 20°C. The test item was also observed to flow as a liquid at temperatures between -20°C and up to 25°C. Therefore for hazard assessment purposes the substance should be considered a liquid at temperatures in excess of -20°C and/or at environmentally relevant conditions.

Conclusions:
The melting temperature (glass transition temperature) was observed at between -49.2 and -53.8°C (or 219 to 224K). The mean glass transition (n = 3) temperature was -52.1°C (or 221K). At this temperature the substance is considered to be liquid.
Executive summary:

The melting/freezing temperature was determined using OECD TG 102 and EU Method A.1 - Differential Scanning Calorimetry under GLP. The guideline defines the melting temperature as: the temperature at which the phase transition from solid to liquid state occurs at atmospheric pressure and this temperature ideally corresponds to the freezing temperature. The glass transition was determined as the average glass transition temperature obtained from Experiment 1 (-49.18°C) and Experiment 2 (-53.79°C) and Experiment 3 (-53.44°C) and the mean was determined to be -52.1°C (or 221K) by using DSC. Applicant assessment indicates the substance should be considered a liquid at temperatures in excess of -20°C and/or at environmentally relevant conditions.

Description of key information

Mp: Glass transition temperature – 52.1°C (or 221 K) at 1 atm, substance is liquid, OECD TG 102 - Thermal Analysis Method, 2018

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
-52.1 °C

Additional information

Key study : OECD TG 102, 2018 : The melting/freezing temperature was determined using OECD TG 102 and EU Method A.1 - Differential Scanning Calorimetry under GLP. The guideline defines the melting temperature as: the temperature at which the phase transition from solid to liquid state occurs at atmospheric pressure and this temperature ideally corresponds to the freezing temperature. The glass transition was determined as the average glass transition temperature obtained from Experiment 1 (-49.18°C) and Experiment 2 (-53.79°C) and Experiment 3 (-53.44°C) and the mean was determined to be -52.1°C (or 221K) by using DSC. Applicant assessment of the DSC curve indicates: the substance appears to have constituents that possess amorphous solid properties at low temperatures (< 20 °C) and possesses a Glass Transition Temperature (Tg) analogous to the conventional ‘melting point’ as defined under the OECD TG 102 guideline. This is a temperature point where the substance possesses glass form as opposed to possessing super-cooled liquid form. For hazard assessment the substance should be treated as a liquid. This is based on the bulk properties of the test item being clearly ‘liquid’ as defined in Regulation (EC) 1272/2008: Annex I, section 1.0. In that the substance is not gaseous and has a vapour pressure < 300 kPa at 50°C and/or has an ‘initial melting point’ at < 20°C. The test item was also observed to flow as a liquid at temperatures between -20°C and up to 25°C. Therefore for hazard assessment purposes the substance should be considered a liquid at temperatures in excess of -20°C and/or at environmentally relevant conditions.