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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
GLP compliance:
not specified
Type of method:
differential scanning calorimetry
Key result
Atm. press.:
1 013 hPa
Decomposition:
yes
Decomp. temp.:
60 - 260 °C
Remarks on result:
not determinable
Remarks:
melting point not identifyable due to decomposition
Conclusions:
In a study conducted according to OECD Guideline 102, the melting point of C12 AAPB was investigated using differential scanning calorimetry (DSC). A melting point was not identifyable due to decomposition in the range between 60 and 260°C.
Executive summary:

In a study conducted according to OECD Guideline 102, the melting point of C12 AAPB was investigated using differential scanning calorimetry (DSC). The DSC-curve showed in the first heating run a defined endothermic signal in the range between 30 and 100°C.

The peak at ca. 76°C with an offset temperature of 66°C has a heat flow of approx. 113 J/g. This is within the typical range for melting processes of an organic material. Further DSC tests in the temperature range -70 to 130°C with three heating cycles were done. However, in the cooling runs and the following second and third heating runs no peak was observed in the range of 76°C. A further big peak was observed in the range from 190 to 260°C. The heat flow, proportional to the peak area was determined as ca. 128 J/g. This is also within the typical range for melting processes of an organic material. However, both in the cooling run and the following second heating run no peak was observed in the range of 238°C as is expected for a typical, reversible melting process. Hence the signal observed at 76 and 238°C during the first heating run does not reflect typical melting processes, but processes when C12 AAPB decomposes, possibly associated with a melting process. In summary, a melting point was not identifyable due to decomposition of the test material.

Description of key information

Coco AAPB: fraction C8/C18: m.p.: 208°C; fraction C8/C10: m.p.: 55-60°C; fraction C12/C14: m.p.: 69-187°C
C8-18 AAPB: not identifyable due to decomposition of the test substance in the range between 208 and 280°C
C12 AAPB: not identifyable due to decomposition of the test substance in the range between 60 and 260°C

Key value for chemical safety assessment

Additional information

In studies conducted according to OECD Guideline 102, the melting points of C8 -18 AAPB and C12 AAPB were investigated using differential scanning calorimetry (DSC). Melting points were not identifyable due to decomposition at temperature ranging from 208 to 280 (C8 -18 AAPB) and 60 and 260°C (C12 AAPB). Based on these results it can be assumed that a weak chemical bond is present in the molecule which is unstable towards elevated temperatures. All AAPBs are similar in structure, contain all the same zwitterionic structure. They differ, however, by their carbon chain length distribution and the degree of unsaturation (<=20%) in the fatty acid moiety. The content of minor constituents in all products are comparable and differ to an irrelevant amount. Based on the available data, it can be assumed that chain length distribution and degree of unsaturation of the fatty acid chain have no or at the most a minor impact on this endpoint.

The melting points of the different fractions of Coco AAPB determined via the capillary method are judged as not reliable as the method does not distinguish between a real melting process and a reaction/decomposition process and as comparable temperatures were found as decompostion temperature in the DSC measurements.