Registration Dossier

Physical & Chemical properties

Auto flammability

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
auto-flammability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study is not to current guidelines or conducted under GLP, however the data obtained is undeniably conclusive.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The test material is heated in a closed cell and the temperature and pressure within the cell monitored.
GLP compliance:
no
Remarks on result:
other: An onset temp of 84oC was detected. A runaway reaction was triggered with a maximum temp recorded of 269.5oC and a pressure of 49.4 bar after which point the cell failed.

 

Exothermic activity was detected at 84°C at a rate of 0.06°C/min. It accelerated to a violent and rapid exotherm producing a significant pressure rise. The rate of pressure rise was > 100 bar/min as the PHI-TEC cells pressure compensation system was unable to compensate, resulting in the failure of the cell. The point of cell failure is clearly visible in Figure 3 attached. The change in the slope just prior to cell failure is typical as the cell balloons and deforms beyond its elastic limit.

 The temperature and pressure profile is attached as Figure 2. 

The measured self-heat rate and rate of pressure rise are illustrated in Figures 4 and 5 attached. The measured values are a gross under estimation of the actual rates that would have been experienced if the cell had remained intact. Further interpretation of the data suggests non-condensable gas generation from the detected onset of thermal activity (around 85°C).

 

The reported enthalpy of reaction was calculated from the detected onset to the point of cell failure, this was calculated to be -400J g reactants-1, this is considered to be an underestimation as the reaction could not be tracked to completion.

 

Exotherm Onset temperature (°C)

84.3

Exotherm Onset Rate (°C/min)

0.06

Onset Pressure (bar)

1.81

Final Temperature (°C)

269.5*

Final Pressure (bar)

49.4 *

Maximum Self-Heat Rate(°C)

298*

Maximum Rate of Pressure Rise (bar /min)

202*

*Maximum values recorded prior to cell failure.

 

 

 

Conclusions:
The test substance undergoes a rapid and violent thermal decomposition when heated adiabatically, the onset temperature being around 84°C.
Executive summary:

The thermal runaway potential of a sample of 4-Oxo Tempo concentrate was measured at Hazard Evaluation Laboratories Limited using the technique of adiabatic calorimetry. The sample was placed in an adapted calorimeter with the potential to control the temperature and pressure of the equipment to mirror that inside the calorimeter. Data on the temperature of the sample and the pressure inside the calorimeter was collated.

The test sample was charged to the test cell, the initial temperature of the test cell was 40°C. The cell was heated in 10°C steps with a waiting period of 17 minutes between increments. This was continued up to a maximum temperature of 230°C. The resulting exotherm was tracked adiabatically within the limits of the apparatus.

 

Exothermic activity was detected at 84°C at a rate of 0.06°C min. This accelerated to a violent and rapid exotherm producing a significant pressure rise. The pressure compensation system of the apparatus was insufficient to compensate for the pressure rise and the cell failed.

 The maximum temperature and pressure recorded prior to the cell failure were 269.5°C and 49.4 bar.

 The enthalpy of reaction was calculated to be -400 J g reactants-1, however this was considered to be an underestimation of that likely to be observed due to the cell failure.

In conclusion, the test substance undergoes a rapid and violent thermal decomposition when heated adiabatically, the onset temperature being around 84°C.

Endpoint:
auto-flammability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
June 1999
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No appropriate guideline is available for the work nor was it performed to GLP, however it was carried out at a reputable laboratory.
Qualifier:
no guideline available
Principles of method if other than guideline:
DSC analysis performed on various samples of 4-Oxo Tempo and 4-Oxo Tempo Hydroxylamine as manufactured or in solution in ethyl benzene.
GLP compliance:
no

The heat outputs from the individual DSC traces are summarised in the following tables. The traces are generally similar, the first activity being a double exotherm, with some further exothermic activity at higher temperatures. There are no obvious baselines from which to take comparative data therefore interpretation of the traces at the higher temperatures is difficult. Integration of these sections of the DSC trace has been performed in two ways, firstly by taking a horizontal baseline from the onset of exothermic activity and secondly from this point to the end of the experiment (400°C).

The horizontal baseline appears to be the worst case, however it was noted that baselines can fall during reaction. As a result of the difficulties in defining a baseline, the data should be treated with caution.

Two samples gave traces which were slightly different, samples 3 and 6.

Sample 3, 4-oxo tempo hydroxylamine is a solid; the trace showed an endotherm at 85°C which is consistent with the solid melting. Unlike the other samples, only a single isotherm is observed as the first exothermic activity however the remainder of the trace is in line with other samples.

Sample 6, 5% solution of 4-Oxo Tempo hydroxylamine in ethyl benzene, showed a large exotherm at ~360°C. This is thought to be due to failure of the test cell and vaporisation of the ethyl benzene. The test cells are rated to 20 bar at 220°C, the vapour pressure of ethyl benzene at 350°C is in excess of 36 bar. Integration of this peak is difficult, the overall enthalpy for this sample (628 Jg-1) is higher than the less dilute samples, this is not expected and is due to defining the baseline and the apparent leak. The first double peak has a lower enthalpy and this is consistent with the stronger solutions.

The DSC traces for all samples and integrations are attached for reference under ‘background information’.

Sample 1: 40% 4-Oxo tempo in ethyl benzene (EP/306/73/5)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

101

211

211

Peak max at°C

197

365

307

End set,°C

211

400

400

Heat output, Jg-1

469

1149

366

Total heat output, Jg-1

-

1618

835

 

Sample 2: 4-Oxo tempo concentrate (EP/306/77/7)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

98

191

191

Peak max at°C

185

400

201

End set,°C

191

400

380

Heat output, Jg-1

854

1764

567

Total heat output, Jg-1

-

2618

1421

 

Sample 3: 4-Oxo tempo hydroxylamine (DER/344/3/1)

 

Endotherm

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

73

144

196

196

Peak max at°C

87

191

323

212

End set,°C

90

196

400

371

Heat output, Jg-1

-90

708

3101

1200

Total heat output, Jg-1

-

-

3899

1908

 

Sample 4: 4-Oxo tempo hydroxylamine (DER/344/3/3)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

97

211

211

Peak max at°C

199

326

309

End set,°C

208

400

391

Heat output, Jg-1

359

1117

378

Total heat output, Jg-1

 

1476

737

 

Sample 5: 4-Oxo tempo hydroxylamine (DER/344/3/2)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

109

210

210

Peak max at°C

198

300

300

End set,°C

210

400

398

Heat output, Jg-1

393

892

385

Total heat output, Jg-1

-

1285

778

 

Sample 6: 5% 4-Oxo tempo in ethyl benzene (DER/344/4/1)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

148

280

N/A

Peak max at°C

200

400

N/A

End set,°C

241

400

N/A

Heat output, Jg-1

73

555

N/A

Total heat output, Jg-1

-

628

N/A

 

Sample 7: 10% 4-Oxo tempo in ethyl benzene (DER/344/4/2)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

131

271

271

Peak max at°C

210

317

317

End set,°C

261

400

398

Heat output, Jg-1

128

348

103

Total heat output, Jg-1

-

476

231

 

Sample 8: 15% 4-Oxo tempo in ethyl benzene (DER/344/4/3)

 

Double Peak

2ndPeak, Integration 1

2ndPeak, Integration 2

Onset,°C

112

247

260

Peak max at°C

205

386

304

End set,°C

232

400

400

Heat output, Jg-1

179

444

149

Total heat output, Jg-1

-

623

328

 

 

Conclusions:
Four different strengths of 4-Oxo Tempo solutions were tested. The results show that the stronger solutions have higher decomposition energies. Due to problems defining the baselines, is it difficult to make recommendations regarding decomposition energy and dilutions required to reduce this to below the 300 Jg-1 threshold.
Executive summary:

Samples of 4-Oxo Tempo and solutions of 4-Oxo Tempo at various concentrations in ethyl benzene, in addition to samples of 4-Oxo Tempo hydroxylamine were analysed by DSC. All samples, with the exception of one sample of 4-Oxo Tempo hydroxylamine showed initial exothermic activity as a doublet followed by further exothermic activity at higher temperatures. A sample of 5% Oxo Tempo in ethyl benzene showed a large endotherm at 360°C, this is thought to be a result of the test cell failing and ethyl benzene evaporation.

Integration of the peaks at the higher temperatures was difficult due to the inconsistent baselines. As a result multiple integrations were performed and reported. The results proved difficult to report accurately.

The results did show that stronger solutions gave higher decomposition energies.

Endpoint:
auto-flammability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
July 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The data was generated by the Health & Safety Laboratory, Buxton, UK, which is an agency of the Health and Safety Executive. The data was generated in order to determine a safe concentration for transport of solution of 4-Oxo Tempo in Ethyl Benzene and was performed in accordance with ‘United Nations Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria. The source is considered to be reliable although the data was no generated to GLP.
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
other: Detonation Test: Test series A - Test A.5 UN GAP Test
Qualifier:
according to
Guideline:
other: Deflagration Test: Test series C- Test C.2 TNO Deflagration Test
Qualifier:
according to
Guideline:
other: Heating under Confinement: Test series E – Test E.2 Dutch Pressure vessel Test
Qualifier:
according to
Guideline:
other: Explosive Power: Test series F - Test F.1 Ballistic Mortar IIId
Qualifier:
according to
Guideline:
other: Thermal Stability test: Test series H – Test H.4 Heat Accumulation Storage Test

Detonation Test: Test series A - Test A.5 UN GAP Test

Sample

Fragmentation

Result

Length (mm)

Type

Trial 1

Trial 2

Average

40% 4-Oxo Tempo in EB

225

190

208

Petalling

Negative

Reference (water)

 

250

 

Petalling

-

 

Under then test conditions, a 40% solution of 4-Oxo tempo in ethyl benzene generates tube damage no worse than the inert reference substance and does not propagate a detonation.

 

Deflagration Test: Test series C- Test C.2 TNO Deflagration Test

Sample

Result

Raw Data

(mm.s-1)

Average

By criteria

40% 4-Oxo Tempo in EB

< 0.25

<<0.25

< 0.25

No

 

A 40% solution of 4-Oxo Tempo in ethyl benzene does not propagate a deflagration under low confinement.

 

Heating under Confinement: Test series E – Test E.2 Dutch Pressure vessel Test

Sample

Mass (g)

t1a(s)

t2b(s)

Critical Orifice (mm)

Result

40% 4-Oxo Tempo in EB

10.0

60

60

1.0 < 3.5

Low

at1– time to reaction (jetting from orifice)

bt2– duration of reaction before rupture of the disk

A 10g sample of 40% 4-Oxo Tempo in ethyl benzene ruptures the bursting disk when a 1.0 mm orifice plate but no rupture occurs with a 3.5 mm orifice. By the criteria used for transport classification, the material exhibits a ‘low’ effect.

Explosive Power: Test series F - Test F.1 Ballistic Mortar IIId

Sample

Displacement (mm)

Explosive power

(% Picric Acid)

Result

40% 4-Oxo Tempo in EB

26.0a

0.05

No

Picric acid (Reference)

406.0b

-

-

Boric acid (Inert)

24.5

-

-

 

aAverage of 3 determinations (25,26 and 27 mm displacement)

bAverage of 10 determinations (standard deviation 12mm)

A 40% solution of 4-Oxo tempo in ethyl benzene exhibits ‘No’ explosive power by the criteria of UN Test Series F Test F.1.

 

Thermal Stability test: Test series H – Test H.4 Heat Accumulation Storage Test

The following test was performed on a sample of 4-Oxo Tempo 20% w/w solution in ethyl benzene.

Mass

Time (hours)

Temperatures

Initial (g)

Final (g)

Loss (%)

Tambto T(oven-2K)

Tambto Toven

Tovento Tmax

Tmax(°C)

ΔT (K)

356.1

347.7

2.4

34.7

42.4

19.7

77.2

1.6

 

During the course of the test, the test substance was exposed to a temperature averaging 75.5°C and never falling below 75°C. Over the seven day test period the sample temperature exhibited a maximum temperature of 1.6K above the oven temperature. The sample lost 2.4% of is mass during the test.

As the temperature rise of the test substance was < 6K at 75°C, the self-accelerating temperature of the 20% solution of 4-Oxo Tempo is greater than 75°C.

 

 

 

Conclusions:
The results from the studies performed show that a 40% w/w solution of 4-Oxo Tempo in ethyl benzene does not detonate, deflagrate or meet explosive criteria under the conditions of the tests. Using the criteria for transport classification, the risk of the substance heating under confinement in the Dutch Pressure Vessel Test is considered low.
Thermal stability testing on a 20%w/w/ solution of 4-Oxo Tempo in ethyl benzene showed that self-accelerating decomposition temperature to be greater than 75°C.
DSC performed by the Hazard Evaluation Laboratory on a 40% solution of Oxo Tempo in ethyl benzene showed an enthalpy of decomposition well in excess of 300Jg-1 (1). Heat accumulation storage test performed by Chilworth Technology Limited (see attached file J7993sr.R01/99, S.M. Rowe) showed the self accelerating decomposition temperature (SADT) for a 50kg package to be less than 75°C but greater than 55°C. A solution of this strength is a candidate for classification as a self reactive liquid UN Class 4 Division 4.1.
In order to define a self reactive ‘type’ for the transport classification, the results from this study and those performed by Chilworth(2) are combined.
As only one Series A detonation test is necessary, the results show that the 40% solution does not propagate a detonation.
The negative results in the deflagration test obtained in this study and the negative results obtained by Chilworth for the time/pressure test (2) conclude that a 40% solution of Oxo Tempo in ethyl benzene does not propagate deflagration.
Heating under confinement requires two results, the conclusion for transport being drawn from the more severe result. The Koenen test performed by Chilworth (2) gave a negative result, however the Dutch Pressure vessel test in this study gave a ‘Low’ result. Applying the classification flow chart for self reactive substance (UN format) a self-reactive liquid ‘Type F’ is assigned.
Transport of Type F self-reactive substances in bulk requires the permission of the Competent Authority in the country of origin.
The thermal stability testing of 20% 4-Oxo Tempo solution in ethyl benzene showed that when the concentration of Oxo tempo is reduced, the SADT for a 50 kg package does not meet the criteria for a self reactive substance of UN division 4.1. The primary hazard for the 20% solution is the flammability of the solvent (ethyl benzene).
Transport of 20% Oxo Tempo solution in ethyl benzene requires that the IBC’s/tanks used are capable of venting the decomposition products arising from any self-decomposition or fire engulfment.
Executive summary:

A series of tests were performed on a sample of 40% 4-Oxo Tempo in ethyl benzene in order to determine the required transport classification. The tests performed were the Detonation Test (Test series A.5, UN GAP Test), Deflagration Test (Test C.2 TNO Deflagration test), Explosive Power (Test F.1 Ballistic Mortar IIId) and Heating under Confinement (Test E.2 Dutch Pressure vessel Test). In addition a Thermal Stability Test, (Test H.4 heat accumulation Storage Test) was performed on a sample of 20% 4-Oxo Tempo in ethyl benzene.

In summary, the 40% solution of 4-Oxo Tempo in ethyl benzene did not propagate a detonation, deflagration or exhibit any explosive power. Test E.2, the Dutch Pressure Vessel Test, showed a ‘low’ effect when heated under confinement.

The results of ‘heating under confinement’ for the 20% solution of 4-Oxo Tempo in ethyl benzene, showed a temperature rise of <6K at 75°C, therefore the self-accelerating temperature of the sample is greater than 75°C.

The results from the study were considered in conjunction with Differential Scanning Calorimetry analysis performed at the Hazard Evaluation Laboratory (R McIntosh, D. Tee: Differential canning Calorimetry on Eight Samples containing 4-Oxo Tempo. Hazard Evaluation Laboratory Report, G:\H-Report\Marksoxo.dsc\H705.) and Explosivity Testing (I. Livingston, 4-Oxo Tempo in Ethyl Benzene, Explosivity Testing, J8035IL.r01/99).

Based on the results considered a 40% solution of 4-Oxo Tempo in ethyl benzene is classified as UN Class 4, Division 4.1, Type F for transport purposes.

When the concentration of 4-Oxo Tempo in the solution is reduced to 20%, the SADT of the solution does not meet the criteria for transport classification as a self reactive substance UN Division 4.1. It is considered that the primary hazard of solutions of this strength is the flammability of the solvent.

Description of key information

4-Oxo Tempo is susceptible to undergoing rapid and violent thermal decomposition when heated adiabatically. The onset temperature is around 84°C. 

Key value for chemical safety assessment

Autoflammability / Self-ignition temperature at 101 325 Pa:
84 °C

Additional information

The thermal runaway potential of a sample of 4-Oxo Tempo concentrate (as manufactured) was determined using adiabatic calorimetry by Hazard Evaluation Laboratories (HEL)(Tee, Waldram, 1999). Exothermic activity was detected at 84°C at a rate of 0.06oC/min, accelerating to a violent and rapid exotherm resulting in a significant pressure rise. Accurate information on the maximum temperature, pressure and enthalpy of reaction was not determined due to failure of the test cell, although the highest recorded were 269.5°C, 49.4 bar with a calculated enthalpy of reaction of -400 J/g reactants-1.

The substance is marketed in solution, in order to safely transport the product, the Health and Safety Laboratory (Brown, Fletcher, 1999) conducted a series of tests to determine a classification for transport. A 40% solution of 4-Oxo Tempo in ethyl benzene is classified as ‘self-reactive substance Type F.’ Further testing on 20% solution of 4-Oxo Tempo in ethyl benzene does not required classification as a self reactive substance. Therefore based on this supporting data, it is fair to assume that the self-reacting potential is due to the 4-Oxo Tempo and not the ethyl benzene, and that the potential will be greater for the pure substance than the 40% solution, as observed in the calorimetry work.

Supporting data is also presented in the form a Differential Scanning Calorimetry (McIntosh, Tee, 1999) performed on a number of samples of 4-Oxo Tempo in solution. The results illustrate the exotherm observed due to the thermal decomposition of the substance. 

In summary the experimental work performed in the key study (Tee, Waldram, 1999) illustrates conclusively the potential of the substance to decompose violently on heating. The classification derived from the work performed on the 40% solution by the Health and Safety Laboratory is considered appropriate for the pure substance.

4-Oxo Tempo is classified as ‘Self reactive substance Type F’.