Sodium azide

Explosiveness

Link to relevant study record(s)

Reference

Endpoint:

explosive properties of explosives

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-01-06 - 2010-01-12

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

EU Method A.14 (Explosive properties)

Deviations:

yes

Remarks:

: thermal sensitivity was additionally tested using a 1.5 mm orifice plate.

GLP compliance:

no

Specific details on test material used for the study:

Chemical Name: sodium azide, NaN3
CAS No.: 26628-22-8
Molar mass: 65.01 g/mol
Molecular formula: N3Na
Physical state: solid
Purity: 99.3%
Bulk density: 0.86 g/ml
Origin of the sample(s): Island Veer Chemie Private Ltd.
Lot. No. of vendor: SA0801149
Raw material code: R1024
Lot No.: R1024-0077

Key result

Parameter:

sensitiveness to impact: impact energy (J)

Remarks on result:

not sensitive to impact using an impact energy of 40 J

Remarks:

With an impact energy of 40 J the sample showed no reaction in 6 trials. The average sound pressure level measured with an audio analyzer is an additional criterion for a positive result. The apparatus itself has a level of 97 dB. The measured sound pressure level was maximum 97.5 dB. The limiting impact energy is > 40 J. The substance is not sensitive to impact.

Key result

Parameter:

sensitiveness to friction: friction load (N)

Remarks on result:

not sensitive to friction using a friction load of 360 N

Remarks:

With a load of 360 N the sample showed no reaction in 6 trials. The limiting load is > 360 N. The substance is not sensitive to friction.

Key result

Parameter:

thermal sensitivity - Koenen test: diameter of the orifice plate

Number of fragments:

0

Remarks on result:

other: With an orifice diameter of 2.0 mm the tube was unaffected or the bottom of the tube was bulged (fragmentation pattern “0” or “A”).

Key result

Parameter:

thermal sensitivity - Koenen test: diameter of the orifice plate

Number of fragments:

0

Remarks on result:

other: With an orifice diameter of 1.5 mm the bottom of the tube was bulged (fragmentation pattern “A”).

Key result

Parameter:

thermal sensitivity - Koenen test: diameter of the orifice plate

Number of fragments:

2

Remarks on result:

other: With an orifice diameter of 1.0 the substance explodes in the first trial resulting in a fragmentation of the tube into two pieces (fragmentation pattern “E”).

Key result

Parameter:

thermal sensitivity - Koenen test: limiting diameter (mm)

Value:

1.5

Koenen test:

In all trials the reaction starts within 14 – 17 sec, resulting in a hissing flame of 0.3 m in height. With an orifice diameter of 2.0 mm and 1.5 mm the tube was unaffected or the bottom of the tube

was bulged (fragmentation pattern “0” or “A”). With an orifice diameter of 1.0 the substance explodes in the first trial resulting in a fragmentation of the tube into two pieces (fragmentation pattern “E”).

Additional trials with an orifice diameter of 6.0 mm are not necessary and have been skipped.

The substance shows no violent effect on heating under confinement with an orifice diameter of 2 mm. The limiting diameter is less than 1.5 mm.

Sample / Lot no.	orifice diameter	amount	start of reaction	fragmentation
R1024-0077	2.0 mm	28.5 g	16 sec	0
	2.0 mm	28.5 g	14 sec	0
	2.0 mm	28.5 g	14 sec	A
	1.5 mm	28.4 g	15 sec	A
	1.5 mm	28.5 g	17 sec	A
	1.5 mm	28.4 g	16 sec	A
	1.0 mm	28.4 g	15 sec	E
	1.0 mm	-	-	-
	1.0 mm	-	-	-

Impact sensitiveness

With an impact‐energy of 40 J the sample showed no reaction in 6 trials. The average sound pressure level measured with an audio analyzer is an additional criterion for a positive result. The apparatus itself has a level of 97 dB. The measured sound pressure level was maximum 97.5 dB.

The limiting impact energy is > 40 J.

The substance is not sensitive to impact.

Friction sensitiveness

With a load of 360 N the sample showed no reaction in 6 trials.

The limiting load is > 360 N.

The substance is not sensitive to friction.

Additional information

A differential scanning calorimetry (DSC) was performed with a heating rate of 10 K/min. The results show an exothermic response of 758 J/g with the onset of exothermic decomposition being at 378 °C.

Interpretation of results:

GHS criteria not met

Conclusions:

Sodium azide has no explosive properties towards friction, shock or heat.

Executive summary:

The explosivity of sodium azide was tested according to the EU guideline A.14 (Explosive Properties). This includes testing on explosive behavior towards friction, shock, and heating. The only deviation from the guideline comprises the additional testing on thermal explosivity using an 1.5 mm orifice plate, which is not part of the guideline. Moreover, a differential scanning calorimetry (DSC) was conducted to serve as preliminary test on explosive properties.

The DSC showed an exothermic response of 758 J/g with the onset of exothermic decomposition at 378 °C. According to the guidance on information requirements and chemical safety assessment R.7a (Endpoint specific guidance), the benchmark for further testing on explosive properties is an exothermic response of >500 J/g and an onset at <500 °C which is fulfilled in this case.

The further testing according to EU guideline A.14 exhibited no explosivity after exposure of sodium azide to friction or shock. Thermal sensitivity testing resulted in ignition and burning of sodium azide when heated in a steel tube with an orifice of either 1.5 or 2.0 mm diameter. Ignition started at 14 -17 seconds, took 100 - 118 seconds and the flame never exceeded 30 cm of height. Using the 1.5 mm orifice, the steel tube wasn't altered in three of three tests. Using the 2.0 mm orifice, the steel tube was unaffected in two of three tests, in the third test, the bottom of the tube plunged out, which cannot be regarded as explosion according to the guideline.

Taken together, sodium azide is not sensitive towards friction, shock, or heat.

Description of key information

The explosivity of sodium azide was tested according to the EU guideline A.14 (Explosive Properties). This includes testing on explosive behaviour towards friction, shock, and heating. The only deviation from the guideline comprises the additional testing on thermal explosivity using an 1.5 mm orifice plate, which is not part of the guideline. Moreover, a differential scanning calorimetry (DSC) was conducted to serve as preliminary test on explosive properties.

The DSC showed an exothermic response of 758 J/g with the onset of exothermic decomposition at 378 °C. According to the guidance on information requirements and chemical safety assessment R.7a (Endpoint specific guidance), the benchmark for further testing on explosive properties is an exothermic response of >500 J/g and an onset at <500 °C which is fulfilled in this case.

The further testing according to EU guideline A.14 exhibited no explosivity after exposure of sodium azide to friction or shock. Thermal sensitivity testing resulted in ignition and burning of sodium azide when heated in a steel tube with an orifice of either 1.5 or 2.0 mm diameter. Ignition started at 14 -17 seconds, took 100 - 118 seconds and the flame never exceeded 30 cm of height. Using the 1.5 mm orifice, the steel tube wasn't altered in three of three tests. Using the 2.0 mm orifice, the steel tube was unaffected in two of three tests, in the third test, the bottom of the tube plunged out, which cannot be regarded as explosion according to the guideline.

Taken together, sodium azide is not sensitive towards friction, shock, or heat.

Key value for chemical safety assessment

Explosiveness:

non explosive