Lithiumbis(trimethylsilyl)amide

Flammability

Description of key information

Flammability (solids): Lithium hexamethyldisilazide is classified as highly flammable.
Substances which in contract with water emit flammable gases: Lithium hexamethyldisilazide showed an evolution of gas in contact with water, but no spontaneous ignition was observed.
Pyrophoric properties: No ignition occured and lithium hexamethyldisilazide does not have to be classified as "pyrophoric substance".
Self-heating Substance: Due to a positive result at 140 °C (2.5 cm cube) the lithium hexamethyldisilazide has to be assigned to Packing Group (PG) II.

Key value for chemical safety assessment

Flammability:

highly flammable

Additional information

Flammability (solids):
Lithium hexamethyldisilazide was tested for flammability according to EU method A.10. Due to the fact that the burning time was faster than 45 seconds, lithium hexamethyldisilazide is classified as highly flammable (CM/RL 20100631.01, 2010).

Substances which in contract with water emit flammable gases:
In two differend studies lithium hexamethyldisilazide was tested for flammability upon contact with water according to UN test method N.5 (FMC 02186, 2002 and RL 20130154.03, 2013). In both studies the test item showed an evolution of gas in contact with water, but no spontaneous ignition was observed. However, for precautionary reasons, the pure substance is classified EU H014 (self-classification by the lead registrant).

Pyrophoric properties:
The pyrophoric properties of lithium hexamethyldisilazide were determined in a study according to UN Recommendations on the transport of dangerous goods – Manual of test and criteria, N.2 Pyrophoric properties (solids; RL 20140176.01, 2014).No ignition was observed within 5 min after the powdery test item was poured from approximately 1 m height onto a non-combustible surface. The test was repeated five times. In none of the six tests an ignition was observed. Due to the results the test item does not have to be classified as "pyrophoric substance", class 4.2, of the Recommendations on the Transport of Dangerous Goods/ Manual of Tests and Criteria and according to chapter 2.10 of the GHS (CLP) regulations.

Self-heating substances:
Lithium hexamethyldisilazide was tested according to the Guideline VDI 2263, sheet 1 (Grewer-oven) which serves as a screening for the classification as "self-heating substance" (RL 20130154.05, 2013). The temperature of the test item showed an exothermic effect starting at 50 °C. From this point on until approximately 400 °C the sample temperature remained slightly above the oven temperature. After the test, the wire-basket was filled to 50%. Due to these results further tests were necessary to classify (or exclude) the test item as "self-heating substance".

Lithium hexamethyldisilazide was tested in two differend studies according to the UN test N.4. In the first study (FMC 02186, 2002) the sample temperature steadily climbed for 7 hours after insertion, from ambient to the oven temperature (140°C), were it stayed for the remainder of the 24 hour test. The sample temperature did not exceed 200°C (60°C above the oven temperature), so no further testing was required. The test substance did not show any auto ignition in this study.
In a second study (RL 20140176.02, 2014) the exothermic effect started at approximately 60°C. The exothermic effect showed a very fast self-ignition of the test item. The maximum temperature of the test item was 553 °C. After the measurement the mesh wire basket contained approximately 84 wt.% less test item than at the start. The temperature of the test item exceeded 200 °C. Due to this positive result at 140 °C (2.5 cm cube) the test item has to be assigned to Packing Group (PG) II.

Based on the latest test, the substance was classified "self-heating".

Justification for classification or non-classification

Classification, Labelling and Packing Regulation (EC) No 1272/2008

Based on data available and taking into account the provisions laid down in Regulation (EC) No 1272/2008, as amended for sixth time in Regulation (EC) No 605/2014, the substance was classified
- flammable cat. 1, H228 (Flammable Solid)
- self-heating substances and mixtures cat. 1, H251 (Self-heating; may catch fire).
The substance is not considered to be classified as flammable in contact with water or pyrophoric.
For precautionary reasons, the lead registrant classified the pure substance  EU H014 (Reacts violently with water).

 

Dangerous Substance Directive (67/548/EEC)

The available studies were considered reliable and suitable for classification purposes under 67/548/EEC as amended for the 31st time in Directive 2009/2/EC. As a result the substance needsed to be classified and labelled as
- F; R11 highly flammable
For precautionary reasons, the lead registrant classified the pure substance R14; Reacts violently with water.