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Physical & Chemical properties

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:
2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
GLP compliance:
not specified
Type of method:
thermal analysis
Key result
Melting / freezing pt.:
4 °C
Atm. press.:
1 atm
Decomposition:
no
Sublimation:
no
Remarks on result:
other: OECD 102 suggests that melting should be reported as a range marked by onset and endset of melting peak. Hence the melting range of TMXDI is 4-12 °C. However the ASTM method and SOP used states to report the onset as the melt. So the reported m.p. is 4°C.

The attached DSC curve shows that TMXDI initially undergoes a glass transition at -69°C. As TMXDI is heated further, molecules tend to form a more ordered package which is confirmed by the crystallization peak at -24°C. The crystallization takes place in between the glass transition and the melting point. After which, the melting point is observed at 4°C.  However, when TMXDI is cooled from ambient to lower temperatures, only a crystallization peak is observed at -8°C. This occurrence does not coincide with observations in constant temperature bath or cold-stage microscopy. In fact, a sample beginning at ambient left in constant temperature bath overnight a -20°C was still a liquid after 24 hours. It is only after cooling under liquid nitrogen initially (~-100°C) that a melt is observed at 4°C in the bath and by optical microscopy.

Conclusions:
The observed melting point of the test material was found to be 4°C and the corresponding melting range was 4-12°C.
Executive summary:

A study was performed to determine the melting point of the test material using differential scanning calorimetry (DSC) and cold-stage optical microscopy techniques. The study was conducted according to OECD Guideline 102.

Duplicate runs were performed to determine the melting point of the test material using indium as the reference material to calibrate the instrument (Mettler 821e DSC). Both the reference standard and the test material was scanned at 10°C/min. The melting point observed through DSC was confirmed by cold-stage optical microscopy and observing the test material at constant temperature bath.

 

Under the test conditions, the melting point of the test material was determined to be 4°C and the melting range was found to be 4 -12°C.

Description of key information

The melting point was determined according to OECD Guideline 102 (Rivera, 2010).

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
4 °C

Additional information