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Melting point / freezing point

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Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
April - May 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
differential scanning calorimetry
Specific details on test material used for the study:
- Description: pale yellow crystalline solid
- Batch number: 7X18A
- Storage conditions: approximately 4°C in the dark over silica gel
Key result
Melting / freezing pt.:
286 °C
Decomposition:
no
Sublimation:
no
Remarks on result:
other: atmospheric pressure not measured

The following endothermic effects were observed:

- 221°C (494 K): loss of impurity/solvent

- 286°C (559 K): melting of sample

After melting, a yellow residue was seen around the periphere of the crucible.

Conclusions:
The test item has a melting point of 286°C (559 K) under the conditions of this study.
Executive summary:

The study was performed accorrding to OECD no. 102 using the Differential Scanning Calorimetry method and performing two measurements. Two endothermic peaks were noted: at 221°C indicating loss of impurity/solvent and at 286°C indicating melting of the test item. In conclusion, the melting point was found to be 286°C (559 K) (mean of two runs).

Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
March - May 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Pyromellitic dianhydride is not stable under certain conditions (e.g. in water). Therefore, a read-across is done to the corresponding decomposition product Pyromellitic acid for several endpoints. The present supporting test with PMA serves as bridging study.
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
differential scanning calorimetry
Specific details on test material used for the study:
- Description: white powder
- Batch number: 8M30N
- Storage conditions: room temperature in the dark upto 04 April 2008, thereafter at approximately 4 °C, over silica gel, in the dark
Key result
Melting / freezing pt.:
286 °C
Decomposition:
yes
Decomp. temp.:
210 °C
Sublimation:
no
Remarks on result:
other: atmospheric pressure not measured

As a result of the low rate of enthalpy change during decomposition, the onset temperature could only be approximated. From information supplied by the Sponsor, the test material decomposed at temperatures above 200°C, resulting in the formation of the anhydride. This is consistent with the broad endotherm observed from approximately 210°C (483 K) which may be attributed to the loss of water liberated from this reaction. Additionally the observed melting temperature of 286°C (559 K) was consistent with an available literature value for the anhydride (melting range 283°C to 286°C). Although no residues remained on completion of each determination, an assessment performed using a metal block apparatus confirmed that the test material melted to a liquid phase. It was suspected that during the DSC analysis at a lower heating rate, the anhydride its-self was volatile or it degraded further to volatile products as heating continued.

Therefore, the overall conclusion was that the test material melted at 286°C (559 K), although it had possibly decomposed from approximately 210°C (483 K). The data generated during the determination supported the Sponsor's information that the test material decomposed on heating to generate the anhydride. Similar thermographic profiles were obtained using air and nitrogen atmospheres; this indicated that the observed decomposition in both determinations was probably thermal and not oxidative.

Conclusions:
The test item has a melting point of 286°C (559 K) under the conditions of this study.
Executive summary:

Melting Point/Melting Range = 286°C (559 K), by differential scanning calorimetry, using ASTM E537-86, OECD Guidelines no. 102, although the test material had possibly decomposed from approximately 210°C (483 K). The data generated during the determination supported the Sponsor's information that the test material decomposed on heating to generate the anhydride.

Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
GLP compliance:
not specified
Melting / freezing pt.:
286 °C
Atm. press.:
other: pressure not available
Decomposition:
no
Sublimation:
no
Conclusions:
The melting point was determined to be 286°C.
Executive summary:

A study similar or equivalent to OECD Guideline 102 (melting point) revealed a melting point of 286°C.

Description of key information

Pyromellitic dianhydride is not stable under certain conditions (e.g. in water). Therefore, a read-across is done to the corresponding decomposition product Pyromellitic acid for several endpoints. The present supporting test with PMA serves as bridging study.

Melting point Pyromellitic dianhydride (PMDA)

The study was performed accorrding to OECD no. 102 using the Differential Scanning Calorimetry method and performing two measurements. Two endothermic peaks were noted: at 221°C indicating loss of impurity/solvent and at 286°C indicating melting of the test item. In conclusion, the melting point was found to be 286°C (559 K) (mean of two runs). In a supporting study similar or equivalent to OECD no. 102, the melting point was determined 286°C.

Melting point Pyromellitic acid (PMA / read-across)

Melting Point/Melting Range = 286°C (559 K), by differential scanning calorimetry, using ASTM E537-86, Method 102 of the OECD Guidelines for Testing of Chemicals, 27 July 1995, although the test material had possibly decomposed from approximately 210°C (483 K). The data generated during the determination supported the Sponsor's information that the test material decomposed on heating to generate the anhydride.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
286 °C

Additional information

Source: GLP-report