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Flammability

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Endpoint:
flammable solids
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Carbide
Target: Fused tungsten carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
UN Manual of Tests and Criteria: Test N.1 (Test method for readily combustible solids)
Version / remarks:
The tests were performed per UN Manual of Tests and Criteria for Transportation of Dangerous Goods, Section 33, Classification Procedures, Test Methods and Criteria Relating to Class 4, Test N.1: Test Method for Readily Combustible Solids.
Principles of method if other than guideline:
The sixth revised edition of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria clarifies that the “whole length of the sample” is to be taken as 100 mm: “Powders of metals or metal alloys should be classified when they can be ignited and the reaction spreads over the whole length (100 mm) of the sample in 10 minutes or less.”
GLP compliance:
not specified
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Several manufacturers submitted samples for testing with Fisher particulate size between 0.21 to 1.43 µm
Key result
Test procedure:
burning rate test over 100 mm length
Remarks:
Avg= 471 sec; FSSS: 0.52 microns
Burning time:
>= 392 - <= 605 s
Key result
Test procedure:
burning rate test over 100 mm length
Remarks:
Avg= 643 sec; FSSS= 1.02 microns
Burning time:
>= 509 - <= 838 s
Interpretation of results:
study cannot be used for classification
Conclusions:
The situation with powders with particles sizes equal to or less than 0.52 µm is less clear as two samples with particles sizes of approximately 0.5 µm met the CLP Cat 2 criteria while two sample of particles sizes less than 0.5 µm did not. Therefore, this dataset is insufficient to draw firm conclusions regarding the flammability classification on tungsten carbide powders with particles size less than 0.58 µm.
Executive summary:

No flammability data of sufficient quality are available for fused tungsten carbide (target substance). However, flammability data are available for tungsten carbide (source substance), which will be used for read-across. Due to the similar chemical constituency and structure between the source substance (tungsten carbide) and the target substance (fused tungsten carbide), the physico-chemical properties would be expected to be the same or sufficiently similar such that application of this read-across is appropriate for this endpoint. For more details, refer to the attached read-across approach document.

Endpoint:
flammable solids
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Carbide
Target: Fused tungsten carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
UN Manual of Tests and Criteria: Test N.1 (Test method for readily combustible solids)
Version / remarks:
The tests were performed per UN Manual of Tests and Criteria for Transportation of Dangerous Goods, Section 33, Classification Procedures, Test Methods and Criteria Relating to Class 4, Test N.1: Test Method for Readily Combustible Solids.
Principles of method if other than guideline:
The sixth revised edition of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria clarifies that the “whole length of the sample” is to be taken as 100 mm: “Powders of metals or metal alloys should be classified when they can be ignited and the reaction spreads over the whole length (100 mm) of the sample in 10 minutes or less.”
GLP compliance:
not specified
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Several manufacturers submitted samples for testing with Fisher particulate size between 0.5 - 1.43 µm.
Key result
Test procedure:
burning rate test: preliminary screening test
Remarks:
Avg= 783.5 sec; FSSS= 0.58 microns
Burning time:
>= 696 - <= 871 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test: preliminary screening test
Remarks:
Avg= 655 sec; FSSS= 0.62 microns
Burning time:
>= 632 - <= 678 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test: preliminary screening test
Remarks:
Avg= 1428 sec; FSSS= 0.64 microns
Burning time:
>= 1 205 - <= 1 651 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test: preliminary screening test
Remarks:
Avg=964.5 sec; FSSS=0.8 microns
Burning time:
>= 846 - <= 1 083 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test over 100 mm length
Remarks:
Avg=643 s; FSSS=1.02 microns, CLP Cat 2
Burning time:
> 509 - < 838 s
Key result
Test procedure:
burning rate test: preliminary screening test
Remarks:
Avg=726.5; FSS=1.04 microns
Burning time:
>= 634 - <= 819 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test: preliminary screening test
Remarks:
Avg=720.5;FSSS=1.22 microns
Burning time:
>= 653 - <= 788 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test over 100 mm length
Remarks:
Avg=952; FSSS=1.31 microns
Burning time:
>= 945 - <= 959 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Key result
Test procedure:
burning rate test over 100 mm length
Remarks:
Avg=1457; FSSS 1.43 microns
Burning time:
>= 1 391 - <= 1 523 s
Remarks on result:
other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.
Interpretation of results:
not classified based on GHS criteria
Conclusions:
Although one sample with a reported particle size of 1.02 µm met the CLP Category 2, the weight of evidence indicates that tungsten carbide powders greater or equal to 0.58 µm in size are not Flammable Solids.
Executive summary:

No flammability data of sufficient quality are available for fused tungsten carbide (target substance). However, flammability data are available for tungsten carbide (source substance), which will be used for read-across. Due to the similar chemical constituency and structure between the source substance (tungsten carbide) and the target substance (fused tungsten carbide), the physico-chemical properties would be expected to be the same or sufficiently similar such that application of this read-across is appropriate for this endpoint. For more details, refer to the attached read-across approach document.

Description of key information

No flammability data of sufficient quality are available for fused tungsten carbide (target substance). However, flammability data are available for tungsten carbide (source substance), which will be used for read-across. Due to the similar chemical constituency and structure between the source substance (tungsten carbide) and the target substance (fused tungsten carbide), the physico-chemical properties would be expected to be the same or sufficiently similar such that application of this read-across is appropriate for this endpoint. For more details, refer to the attached read-across approach document.

Several tungsten carbide powders were tested using the new recommended 100 mm testing train. A total of 15 tungsten carbide powder samples with a Fisher Sub Sieve Size (FSSS) ranging from 0.21 um to 1.43 um. The flammability tests were performed per UN Manual of Tests and Criteria for Transportation of Dangerous Goods, Section 33, Classification Procedures, Test Methods and Criteria Relating to Class 4,Test N.1: Test Method for Readily Combustible Solids.The scope of the laboratory’s accreditation (ISO/IEC 17025:2017) includes DOT 4.1 Ignitability and Burn Rate. Although one sample with a reported particle size of 1.02 microns met the CLP Category 2 criteria, the weight of evidence indicates that tungsten carbide powders greater or equal to 0.58 microns in size are not Category 2 Flammable Solids. The flammability classification for powders with particle sizes equal to or less than 0.52 microns was inconclusive.

Key value for chemical safety assessment

Flammability:
not classified

Additional information

Due to the similar chemical constituency and structure between the source substance (tungsten carbide) and the target substance (fused tungsten carbide), the physico-chemical properties would be expected to be the same or sufficiently similar such that application of this read-across is appropriate for this endpoint. For more details, refer to the attached read-across approach document.

Justification for classification or non-classification

No flammability data of sufficient quality are available for fused tungsten carbide (target substance). However, flammability data are available for tungsten carbide (source substance), which will be used for read-across.

Although one sample with a reported particle size of 1.02 microns met the CLP Category 2 criteria, the weight of evidence indicates that tungsten carbide powders greater or equal to 0.58 microns in size are not Flammable Solids.

The flammability classification for powders with particle sizes equal to or less than 0.52 microns was inconclusive.