Chlorothalonil

Oxidising properties

Link to relevant study record(s)

Reference

Endpoint:

oxidising solids

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 May 1994 to 15 Jul 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.17 (Oxidising Properties (Solids))

GLP compliance:

yes

Contact with:

powdered cellulose

Sample tested:

other: 1:4 test substance:cellulose ratio

Parameter:

mean burning time

Result:

417 s

Key result

Sample tested:

other: 1:9 test substance:cellulose ratio

Parameter:

mean burning time

Result:

423 s

Sample tested:

other: 7:3 barium nitrate:cellulose ratio

Parameter:

mean burning time

Result:

823 s

Sample tested:

other: 3:2 barium nitrate:cellulose ratio

Parameter:

mean burning time

Result:

573 s

Sample tested:

other: 1:1 barium nitrate:cellulose ratio

Parameter:

mean burning time

Result:

708 s

The three fastest reactions for the test substance:cellulose mixture, i.e., 3:7, 1:4, and 1:9, were determined two more times. The mean reaction time of the 1:9 mixture was 7 minutes 3 seconds for the three replicates. Note: The three reaction times (6:57, 7:03, 7:09, min.:sec) did not differ from the mean reaction time by more than 10 %. For replicates 2 and 3 of the 1:4 mixture, the flame sustained for 110 mm and 150 mm, respectively, and then extinguished. The 3:7 mixture extinguished after 20 mm and 30 mm for replicates 2 and 3. Clearly then, the fastest burn rate or reaction time for test substance: cellulose mixtures was achieved for 10 % test substance and 90 % cellulose by mass. The fastest reaction time for barium nitrate : cellulose mixtures was achieved for a 60 % barium nitrate/40% cellulose mixture as predicted in EEC Method A.17. However, this time (9:33) was slower than the mean fastest reaction time for test substance: cellulose mixtures. This was not an expected result. In fact, based on a consideration of the chemical structure of the test substance, and data collected earlier one would have expected observations indicating no oxidizing potential. In light of these observations, further experimentation with the barium nitrate : cellulose combinations was performed. Previously, the barium nitrate material was sieved through a #40 mesh sieve as opposed to a #120 mesh sieve. Therefore, to be consistent, three more mixtures of barium nitrate:cellulose, in the ratio 3:2, respectively, were prepared using barium nitrate that had been sieved through a #120 mesh sieve and dried to constant mass. The reaction times were 7:39, 8:00, and 7:53 (min.:sec) for each replicate and a mean reaction time of 7 minutes 51 seconds. Reducing the particle size of the oxidizer, barium nitrate, clearly reduced the mean reaction time for the mixture; however, it was still longer than the test substance:cellulose mean time. At this juncture, experimentation was ceased. The following discussion addresses the false positive results obtained above.

 

The EEC Method A.17, section 1.1, states that the test need not be performed if examination of the structural formula establishes beyond reasonable doubt that the test substance is incapable of reacting exothermically with a combustible material. As per the Explosive Properties, this theoretical route,supported with published data, was taken. Many of the points of discussion within the Explosive Properties section are relevant to the discussion below; hence, if the reader feels a strong case of deja vu, it is with good cause. At ambient laboratory temperatures, it was demonstrated within this report that the test substance did not ignite or propagate combustion, either by burning with flame or smouldering along 200 mm of a powder train within a 4-minute test period. Based on this observation, reproduced in duplicate, it was concluded that the test substance should not be considered a highly flammable substance.

At temperatures above ambient laboratory temperature, 140 °C, it was demonstrated for Auto-Flammability, that the test substance did not spontaneously ignite over a 24-hour test period. These reported findings, i.e., at ambient laboratory temperature and at 140 °C, support the statements made within the Explosive Properties section where it is stated that the combustion of the test substance cannot be sustained outside a high temperature environment. Further, for a reasonable degree of combustion, the test substance must be placed inside a quartz tube and the latter heated to 700 °C in a furnace and exposed to air flow. The air flow is essential to provide the necessary oxygen for combustion. This test substance has no oxygen of its own to support combustion. From a purely structural standpoint, these findings (Flammability and Auto-Flammability) are not surprising. The test substance comprises molecular species with about half of the under chlorinated homologs. It is well known that some halogen containing compounds, particularly perchlorinated aromatic species, are known to make combustion difficult. A major molecular species of the test substance is comprised of perchlorinated aromatic species. Based on the above described agreement between chemical structural theory and observed flammability properties (Flammability and Auto-Flammability), the oxidizing properties data presents an anomaly , i.e., a false positive, that can only be explained in terms of some physical phenomenon. Cellulose alone was observed to burn only part way, 100 mm, across the 200-mm train. The test substance alone did not burn at all. Hence, by adding a material that does not burn and has no oxygen donation capacity (the test substance) to something that does burn weakly (the cellulose), one would expect the burning rate of the mixture to reduce with respect to cellulose alone and burn out before 100 mm. In essence, it would be akin to mixing sand, a known noncombustible material, to cellulose and comparing the burn rate and propagation distance of the mix to that obtained by cellulose alone. If, however, the packing density of the mix of test substance and cellulose is reduced somewhat during the process of burning relative to the packing density of cellulose alone, it apparently is possible that the burn rate and propagation distance may increase for the mixture. Taking an extreme hypothetical example, one could envisage burning a log of wood 100 mm long of the same mass and degree of moisture as a pile of wood shavings 100 mm long. Clearly, the latter pile, which has a much lower density, would burn and propagate at a much faster rate than the log. The reason for this is clear. The lower density allows air to penetrate to the combustion front more efficiently and the higher effective surface area allows a hotter flame. It is well known that pure test substance sublimes around 150 °C and that a typical laboratory burner can reach temperatures as high as 800 °C . Hence, the subsequent sublimation of some of the test substance in the 1:9 mixture, which releases gaseous test substance, will alter the packing density of the mixture, i.e., reduce it from its original density prior to burning. This physical effect, however small, must provide an explanation for the anomaly reported above. Based on a consideration of all of the pertinent experimental data within this report, i.e Flammability, Auto-Flammability, and sound theoretical discussions within Explosives, we conclude that the test substance is not an oxidizer.

Table 1 Time of Reaction for Barium Nitrate:Cellulose Mixtures

Mixture Barium Nitrate:Cellulose	Time (min:sec)	Observations
9:1	NR	*
4:1	NR	*
7:3	13:43	**
3:2	09:33	**
1:1	11:48	**
2:3	NR	*
3:7	NR	*
1:4	NR	*
1:9	NR	*

NR = Not Reacted, i.e., a flame that did not self sustain and propagate 200 mm across the train.

*   Flame did not sustain and propagate 200 mm.

**  Flame sustained for 10 mm and extinguished.

*** Flame sustained and propagated 200 mm.

Table 2 Time of Reaction for Test substance:Cellulose Mixture

Mixture Test Substance:Cellulose	Time (min:sec)	Observations
9:1	NR	*
4:1	NR	*
7:3	NR	*
3:2	NR	*
1:1	NR	*
2:3	NR	*
3:7	NR	**
1:4	10:50	***
1:9	6:57	***

NR = Not Reacted, i.e., a flame that did not self sustain and propagate 200 mm across the train.

*   Flame did not sustain and propagate 200 mm.

**  Flame sustained for 10 mm and extinguished.

*** Flame sustained and propagated 200 mm.

Table 3 Time of Reaction for Barium Nitrate and Cellulose Only 

Material	Time	Observations
Barium Nitrate	NR	*
Cellulose	NR	*

NR = Not Reacted, i.e., a flame that did not self sustain and propagate 200 mm across the train.

*   Flame did not sustain and propagate 200 mm.

**  Flame sustained for 10 mm and extinguished.

*** Flame sustained and propagated 200 mm.

Interpretation of results:

GHS criteria not met

Conclusions:

The test substance was not considered to be an oxidising solid based on this experimental study and further examination of the physico-chemical data of test substance.

Executive summary:

To determine the oxidizing properties of the substance, a study was performed according to EC Test A.17 and in compliance with GLP. In this study the mean burning times of the 10 % test substance and 90 % cellulose showed that, in combination with further examination of it's physico-chemical data, the test substance does not have oxidising properties.

Description of key information

The fastest burn rate or reaction time for test substance: cellulose mixtures was achieved for 10 % test substance and 90% cellulose by mass. EU Method A.17, Gallacher 1994.

Key value for chemical safety assessment

Oxidising properties:

non oxidising

Justification for classification or non-classification

Based on the available information, classification on oxidising properties is not warranted in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation No. (EC) 1272/2008.