Trichlorosilane

Flammability

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

flammable liquids: obsolete as covered by section 'Flash point'

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is a liquid

Reference 2

Endpoint:

substances / mixtures which in contact with water emit flammable gases

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

UN Manual of Tests and Criteria: Test N.5 (Test method for substances which in contact with water emit flammable gases)

Version / remarks:

Test UN N.5: test method for substances which in contact of water emit flammable gases (according to the UN "Recommendations on the Transport of Dangerous Goods, Manual of Tests & Criteria", ST/SG/AC.10/11, 5th revised edition, 2009, test N.5, page 367-36

Deviations:

no

GLP compliance:

yes

Key result

Test procedure:

step 1

Max. rate of gas release:

58.4 L/kg min

Identity of evolved gas:

as specified:

Remarks on result:

vigorous reaction with water and spontaneous ignition of the evolved gas

Key result

Test procedure:

step 2

Max. rate of gas release:

67.6 L/kg min

Identity of evolved gas:

as specified:

Remarks on result:

vigorous reaction with water and spontaneous ignition of the evolved gas

Key result

Test procedure:

step 3

Max. rate of gas release:

68 L/kg min

Identity of evolved gas:

as specified:

Remarks on result:

vigorous reaction with water and spontaneous ignition of the evolved gas

Table 1: Rate of gas emission

Trial	Sample mass (g)/water (ml)	Maximum rate of gas emission [l/(kg min)]
Trial 1	10.29	58.4
Trial 2	10.13	67.6
Trial 3	9.93	68.0

 

The composition of the evolved gas in the UN Test N.5 was not analysed by BAM.

Flammability testing of evolved gas when mixed with water: first trial

The pressure quickly increased first to 4.2 bar and then to 6.4 bar, the temperature increased up to 68°C. The outlet valve was opened and the gas released. The exhaust gas could not be ignited at first. After about 600 seconds, the outlet valve was closed. The data acquisition was stopped after about 650 seconds. After about 900 seconds, the valve was re-opened and the gas released again. The exhaust gas could now be ignited with a matches.

Flammability testing of evolved gas when mixed with water: second trial

Again the temperature and pressure increased during the reaction reaching values of about 60°C and 4.0 bar. After reaching these highest levels, the temperature and pressure were declining to almost constant values of 26°C and 2.6 bar. The whole autoclave and the outlet valve were cooled down to a temperature of about 0°C before opening the outlet valve. The gas could be ignited just as in the first experiment.

Flammability testing of evolved gas without water: third trial

The outlet valve was opened and again the test could be ignited. The flame could not be differentiated visually from the flames observed in the tests described above.

Interpretation of results:

Category 1 (substances or mixtures which in contact with water release flammable gases which may ignite spontaneously) based on GHS criteria

Conclusions:

Trichlorosilane fulfils the criteria of Division 4.3 "Substance which in contact with water emit flammable gases" packing group I of the UN Recommendation on the Transport of Dangerous Good and the Hazard Class "Substance or Mixtures which in contact with water, emit flammable gases", Category 1 of the Regulatory EC 1272/2008 (CLP/GHS Regulations) because the maximum rate of gas of more than 10 l/(kg min) was determined.

Executive summary:

Trichlorosilane fulfils the criteria of Division 4.3 "Substance which in contact with water emit flammable gases" packing group I of the UN Recommendation on the Transport of Dangerous Good and Hazard Class "Substance or Mixtures which in contact with water, emit flammable gases", Category 1 of the Regulatory EC 1272/2008 (CLP/GHS Regulations) because the maximum rate of gas of more than 10 l/(kg min) was determined.

Reference 3

Endpoint:

substances / mixtures which in contact with water emit flammable gases

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014-11-13

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

The formation of hydrogen during reaction of Trichlorosilane with deionized water was investigated under confinement using a glass apparatus. Assessment criterion was the result of gas chromatographic analysis for hydrogen of gas samples, taken during the testing time

GLP compliance:

no

Key result

Test procedure:

other: The study was performed to confirm the formation of hydrogen

Max. rate of gas release:

1.6 other: Vol%

Identity of evolved gas:

as specified:

Remarks on result:

other: Formation of hydrogen confirmed

Test results:

Test 1: 200 g deionized water and dosing of trichlorosilane in steps of 5.3 g and 4.7 g

A mass of about 200 g deionized water was filled into the reactor which had been previously flushed with argon. Start temperature of the liquid phase was room temperature. A syringe filled with 10 g the test substance (at room temperature) was connected to the reactor.

In a first step dosing the valve was opened and a trichlorosilane mass of 5.3 g was added. The valve was closed afterwards. The first gas sample was taken after about 13 min after starting the test using an evacuated glass sample container which was connected to the glass reactor. Up to this time the reaction gas was in contact exclusively with glass. The pressure transducer was still separated by the Teflon valve.

The sample container could be filled with gas up to normal pressure (no dilution with argon necessary). The GC-analysis showed a hydrogen concentration of only 0.06 Vol.%.

- The gas chromatographic analysis of the reaction gas provides evidence for the formation of hydrogen. The result of the analysis was 0.06 % hydrogen, but is only slight above the detection limit of 0,02 Vol%.

Directly after taking the gas sample, the residual pressure was checked in the glass reactor (P=1.14 bar). For that purpose it was necessary to open the Teflon valve leading to the metal membrane of the

connected pressure transducer during a short time (a few seconds). Within this time period the reaction gas had been in contact with metal.

The second gas sample was taken 3 h after starting test. During filling the evacuated sample container, the pressure of the glass reactor reached the underpressure range due to the available amount of gas.

- The GC-analysis showed a hydrogen concentration of 1.6 Vol.%.

Interpretation of results:

Category 1 (substances or mixtures which in contact with water release flammable gases which may ignite spontaneously) based on GHS criteria

Conclusions:

The formation of hydrogen was confirmed in a reliable study conducted using a relevant test method.

Reference 4

Endpoint:

substances / mixtures which in contact with water emit flammable gases

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014-11-13

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Reason / purpose for cross-reference:

reference to other study

Principles of method if other than guideline:

Quantification of Hydrogen by Gaschromatography in Volume Percent with external Standard, Thermal Conductivity Detector, using a Molecular sieve 5A column, carrier gas argon, oven temperature 35 ºC (isothermal); Syringe injection

GLP compliance:

no

Key result

Test procedure:

other: The study was performed to confirm the formation of hydrogen

Max. rate of gas release:

1.14 other: Vol%

Identity of evolved gas:

as specified:

Remarks on result:

other: Formation of hydrogen confirmed

In all three tests formation of hydrogen was confirmed.

Sample number	Sample name	Number of injections	Concentration Hydrogen	Rel. Standard Aviation
1	142-14-4A	3	0,06 Vol.%	7.44%
2	142-14-4B	3	1,14 Vol.%	0.41%

 

Interpretation of results:

Category 1 (substances or mixtures which in contact with water release flammable gases which may ignite spontaneously) based on GHS criteria

Conclusions:

The formation of hydrogen was confirmed in a reliable study conducted using a relevant test method.

Reference 5

Endpoint:

pyrophoric liquids

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.13 (Pyrophoric Properties of Solids and Liquids)

Version / remarks:

Test UN N.3 on pyrophoric properties (According to the UN "Recommendations on the Transport of Dangerous Goods, Manual of Tests & Criteria", ST/SG/AC.10/11, 5th revised edition, 2009, test N.3, page 363).

Deviations:

no

GLP compliance:

yes

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Key result

Test procedure:

ignition time on contact with air

Remarks on result:

no ignition within 5 minutes

Key result

Test procedure:

effect on filter paper

Temp.:

23 °C

Relative air humidity (%):

51

Remarks on result:

no ignition within 5 minutes

Six tests were performed with the sample, using a prepared porcelain cup (filled with diatomaceous earth, height about 5 mm). Within the prescribed testing time of 5 minutes no ignition of the sample was observed. Afterwards, based on the negative results observed in part one of the test, part two was conducted. Three tests using filter paper were performed at a temperature of 23 °C (measurement using Quat 100 reference thermometer) and a relative humidity of 51 % (measured using Lambrecht hygrometer). Each of the tests showed no ignition or charring of the filter paper within the prescribed testing time of 5 minutes.

Final assessment:

The tested sample indicated no pyrophoric properties.

Interpretation of results:

GHS criteria not met

Conclusions:

The tested sample indicated no pyrophoric properties.

Executive summary:

Trichlorosilane does not fulfil the criteria of Division 4.2 "Pyrophoric liquids" of according to Test UN N.3 on pyrophoric properties (UN "Recommendations on the Transport of Dangerous Goods, Manual of Tests & Criteria", ST/SG/AC.10/11, 5th revised edition, 2009, test N.3, page 363) .

Description of key information

The substance, trichlorosilane:

•       Is extremely flammable (based on a measured flash point of <-19.5°C and boiling point 31.5-33°C)

•       In contact with water emits a flammable gas (UN Test Method N.5).

•       Is not pyrophoric (UN Test Method N.3).

Key value for chemical safety assessment

Flammability:

substances and mixtures which in contact with water emit flammable gases

Additional information

Trichlorosilane is a liquid, so its flammability is assessed on the basis of flash point.

Trichlorosilane produces a flammable gas (hydrogen) in contact with water at a maximum rate of gas of more than 10 l/(kg min), determined by UN Test Method N.5 ( Michael-Schulz 2014). It was not possible to determine the relative amounts of hydrogen and hydrogen chloride gas produced. 

Trichlorosilane was demonstrated to be not pyrophoric in a study performed in accordance with UN Test Method N.3 because it could not be ignited in the first part of the test, and did not ignite or char the filter paper in the second part of the test (Michael-Schulz 2014).

Flammability additional key value for CSA: extremely flammable

Justification for classification or non-classification

Trichlorosilane has a harmonised classification of Flammable Liquid Category 1 (H224: Extremely flammable liquid and vapour) in Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). Trichlorosilane is a liquid, so its flammability is assessed on the basis of flash point. Measured flash point value of <-19.5°C at 101.3 kPa and boiling point values of 31.5 to 33°C at 101.3 kPa are consistent with the harmonised classification for this endpoint.

Trichlorosilane produces a flammable gas in contact with water at a maximum rate of gas of more than 10 l/(kg min), determined by UN Test Method N.5 ( Michael-Schulz 2014). It was not possible to determine the relative amounts of hydrogen and hydrogen chloride gas produced, but it was shown in the additionally performed autoclave experiments, that the gas which was evolved during the reaction of “trichlorosilane” with water is flammable.

It is the opinion of BAM to classify the substance as Water React. Flam. Gas Category 1 independent from the chemical identity of the evolved gas as a worst case scenario. Trichlorosilane is therefore self–classified by the registrants as Water React. Flam. Gas Category 1 (H260: In contact with water releases flammable gases which may ignite spontaneously) according to the criteria of Regulation (EC) No. 1272/2008 (CLP Regulation).

Trichlorosilane has a harmonised classification of Pyr. Liquid Category 1 (H250: Catches fire spontaneously if exposed to air.) in Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). However, in a recently conducted study, performed in accordance with UN Test Method N.3, trichlorosilane was demonstrated to be not pyrophoric because it could not be ignited in the first part of the test, and did not ignite or char the filter paper in the second part of the test ( Michael-Schulz 2014). Therefore, the self-classification proposed by the registrants does not include the Pyr. Liquid Category 1 classification.

In addition, primary alcohols react with chlorosilanes almost as rapidly as water, forming hydrogen chloride; secondary and tertiary alcohols react less rapidly (CES 2003). Ammonia and the aliphatic amines react rapidly with chlorosilanes, generating heat and solids (ammonium and amine salts). Bases react violently with chlorosilanes, generating heat.

Therefore, it is important to keep the substance strictly free of water during manufacture and storage and also prevent contact with other incompatible materials.

     

Reactivity hazards:

The substance reacts vigorously in the presence of water, including moisture in the air. This may present a physical hazard and is reflected in the classification of ‘Reacts violently with water’. One of the products of the reaction is hydrochloric acid, which is classified as corrosive. The reaction includes the formation of hydrogen gas, which is flammable.

Classification and Labelling according to Regulation (EC) No 1272/2008:EUH014: Reacts violently with water.

In addition, primary alcohols react with chlorosilanes almost as rapidly as water, forming hydrochloric acid; secondary and tertiary alcohols react less rapidly (CES, 2003). Ammonia and the aliphatic amines react rapidly with chlorosilanes, generating heat and solids (ammonium and amine salts). Bases react violently with chlorosilanes, generating heat.

Therefore, it is important to keep the substance strictly free of water during manufacture and storage and also prevent contact with other incompatible materials.

Reference:

CES (2003). Centre Européen des Silicones Safe Handling of Chlorosilanes available online @ http://www.silicones.eu/uploads/Modules/Resources/chlorosilanes-manual-22082003.pdf