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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.:
208 - 280 °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 C8 -18 AAPB was investigated using differential scanning calorimetry (DSC). A melting point was not identifyable due to decomposition in the range between 208 and 280°C.
Executive summary:

In a study conducted according to OECD Guideline 102, the melting point of C8 -18 AAPB was investigated using differential scanning calorimetry (DSC). The DSC-curve showed in the first heating run an elongated endothermic signal in the range between 20 and 130°C. This process could be drying of the betaine (loss of residual water and glycerol). A further peak was observed in the range from 209 to 280°C. The heat flow, proportional to the peak area was determined as ca. 136 J/g. This is within the typical range for melting processes of an organic material. So an apparent melting point was identified as the temperature where the observed signal was peaking (244°C). However, both in the cooling run and the following second heating run no peak was observed in the range of 244°C as is expected for a typical, reversible melting process. Hence the signal observed at 244°C during the first heating run does not reflect a typical melting process, but a process when C8 -18 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.