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Explosiveness

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Description of key information

Based on eleven valid available tests, azodicarbonamide is not explosive.

Key value for chemical safety assessment

Explosiveness:
non explosive

Additional information

Eleven different tests are available; all studies have been realised according to the EU method for the evaluation of the explosive properties of a substance A.14 and in compliance to GLP gave negative results in friction sensitivity, in impact sensitivity and in thermal sensitivity:

  • BAM report GLP/II23/040998/01, 1998;
  • BAM report GLP/II23/270897/02, 1997;
  • BAM report GLP/II23/270897/01, 1997;
  • HLS report LBA0003, 2010;
  • BAM report GLP/II23/260695/01, 1995;
  • BAM report GLP/II23/260695/02, 1995;
  • BAM report GLP/II23/260695/03, 1995;
  • BAM report GLP/II23/260695/04, 1995;
  • BAM report GLP/II23/260695/05, 1995;
  • BAM report GLP/II23/260695/06, 1995;
  • BAM report GLP/II23/260695/07, 1995.

No reaction occurred during the friction test, the drop hammer test and the steel tube test. ADCA was therefore not explosive.   Furthermore, in the BAM report on explosivity (1995), different granulometry were evaluated (from 2.2 to 7µ). No reaction occurred during the friction test, the drop hammer test and the steel tube test. ADCA was found negative in friction sensitivity, in impact sensitivity and in thermal sensitivity and therefore not explosive within the range of particle size tested.

ADCA is therefore considered as non-explosive.

Justification for classification or non-classification

1-Classification according to DSD:

Azodicarbonamide is currently classified as E; R2 in the DSD regulation (Directive 67/548/CE, 31st amendment, 2009/2/CEE).

2-Classification according to CLP:

Screening procedure and waiving of the test:

a)     Chemical structure

ADCA contains an azo group (N-N), which are chemical groups associated with explosive properties.

b)     Oxygen balance

The oxygen balance has therefore to be calculated according to the formula:

Oxygen balance = - 1 600 [2x + (y/2)-z]/molecular weight;

[Calculated for the chemical reaction: CxHyOz+ [x+ (y/4)-(z/2)] O2 → x CO2 + (y/2) H2O]

 

In the case of ADCA, x=2, y=4, z=2, and molecular weight=116.08.

The Oxygen balance is -55.13, which is above the -200 threshold.

 

This is confirmed by the Endpoint specific guidance chapter R7A, p 131, as Azodicarbonamide has been used as example for the explosive properties section.This passage hasbeen copied from "7.1.11.5 Integrated testing strategy for explosive properties":

ADCA“…contains an azo group; one of the alert groups for explosive properties. Thus, following the screening procedure, one continues to calculate the oxygen balance. The molecular formula is C2H4N4O2 and the molecular weight is 116.08. These give an oxygen balance of -55.13. This is more than the -200 threshold.

 

c)     Exothermic decomposition energy

According the Amendment to Special Provision 215 on UN 3242 (ST/SG/AC.10/C.3/2001/2, 23 March 2001), by the Committee of Experts on the Transport of Dangerous Goods and on the GHS, Sub-Committee of Experts on the Transport of Dangerous Goods (19thsession, 2-6 July 2001, agenda item 8(d)), transmitted by the International Council of Chemical Associations (ICCA),“AC formulations containing not more than 40% by weight of azodicarbonamide with at least 60% inert have an energy of decomposition of less than 500 J/g”.

 

Mixtures with such low energies of decomposition are not required to be considered as candidates for Class 1 (Manual of Tests and Criteria,Appendix 6: "Screening procedures for substances that may have explosive properties", paragraph 3.3(c)). Paragraph 3.3(c) of Appendix 6 states:

"When the organic substance or a homogenous mixture of organic substances contains chemical groups associated with explosive properties but the exothermic decomposition energy is less than 500 J/g and the onset of exothermic decomposition is below 500 ºC (…).".

 

Above this concentration (40% of ADCA in mixtures), the exothermic Decomposition Energy is above the threshold 500J/g.

 

d)    Mixtures of inorganic substances with organic material

Does not apply for ADCA.

 

 

In summary,ADCA cannot to be exempted from preliminary criteria of GHS/CLP.

According to the screening procedure, ADCA may possess explosive properties and has therefore to be tested for evaluation of the explosive properties based on the test series described in the UN Recommendation on the Transport of Dangerous Goods (Manual of Test of Criteria).



Acceptance procedure

a)     Official data

Relevant data on Azodicarbonamide have already been published in the official text: “UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria (part II)”; those information are as follows:

 

Test 

 Result 

 Additional remarks 

Equivalence

 A.1 

 "no" 

 15 cm fragmented length, apparent density 627 kg/m3

comparable to the UN-Qap test 2(a)

 C.1 

 "yes, slowly" 

 63 ms 

Time taken to pressure rise from 670 kPa to 2070 kPa is more than 30 msàcomparable to 2(c)

 C.2 

 "yes, slowly" 

 0.35 mm 

 

 E.1 

 "medium" 

 Limiting diameter 1.5 mm 

Limiting diameter is less than 2,0 mmàcomparable to 2(b)

 E.2 

"low"

 Limiting diameter 1.5 mm 

 

 F.3 

 "no" 

 9ml/10g 

 

 H.4

 > 75 °C 

 SADT 

 

 

b)     Unpublished data

Eleven unpublished tests realised according to the EU A.14 method and in compliance to GLP assessed the sensitivities to heat, friction and impact of ADCA:

  1. BAM report GLP/II23/040998/01, 1998;
  2. BAM report GLP/II23/270897/02, 1997;
  3. BAM report GLP/II23/270897/01, 1997;
  4. HLS report LBA0003, 2010;
  5. BAM report GLP/II23/260695/01, 1995;
  6. BAM report GLP/II23/260695/02, 1995;
  7. BAM report GLP/II23/260695/03, 1995;
  8. BAM report GLP/II23/260695/04, 1995;
  9. BAM report GLP/II23/260695/05, 1995;
  10. BAM report GLP/II23/260695/06, 1995;
  11. BAM report GLP/II23/260695/07, 1995.

 

Method A.14 evaluates:

  • Friction sensitivity: as recommended by the Tests series 3(b) Sensitiveness to Friction (BAM friction apparatus),
  • Impact sensitivity: as recommended by the Tests series 3(a) Sensitiveness to Impact (BAM Fallhammer),
  • Thermal sensitivity: equivalent to the Koenen test, as recommended by the Tests series 2(b) Sensitiveness to Heat (BAM thermal sensitivity).

 

No reaction occurred during the friction test, the drop hammer test and the steel tube test. All of the 11 tests were negative for each of the sensitivities tested.

 

c)     Additional information

a.      Granulometry

Furthermore, in these 11 tests, different granulometry were evaluated (from 2.2 to 7µ). No reaction occurred during the friction test, the drop hammer test and the steel tube test. ADCA was found negative in friction sensitivity, in impact sensitivity and in thermal sensitivity and therefore not explosive within the range of particle size tested.

b.     Selfreactive substance

Furthermore, ADCA cannot be classified as a self-reactive substance (CLP-GHS), according to the classification criteria (part 2.8.2.1 – point (e)) of CLP-GHS regulation:“Any self-reactive substance or mixture shall be considered for classification in this class as a self-reactive substance or mixture unless:

(e) their self-accelerating decomposition temperature (SADT) is greater than 75ºC for a 50 kg package (UN Recommendation on the Transport of Dangerous Goods, Manual of Test of Criteria, table 28.4.4.5)”

 

The SADT (self-accelerating decomposition temperature) of a 50 kg package is higher than 75°C (UN Recommendation on the Transport of Dangerous Goods, Manual of Test of Criteria, table 28.4.4.5) for ADCA.

 

 

Summary

According to the available data, either official or unpublished, ADCA is negative in test series 2(a), (b) and (c).

 

Based on these test results and in relation with the criteria of test series 2 and 3, ADCA is too insensitive for acceptance into class 1 (transport) or as an explosive (GHS).  

Nevertheless, violent and dangerous reactions (e.g. explosion) under strong confinement cannot be excluded.