Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

The registration substance has an average purity of >80% 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (Vi4-D4), with <15% 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane Vi5-D5 (CAS 17704-22-2; Impurity 1) and <10% 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane Vi3-D3 (CAS 3901-77-7; Impurity 2) present as impurities. For relevant endpoints, the 3 components are considered separately. The key data relate to the main constituent (Vi4-D4), and may be for this substance or an appropriate read-across. These key data are supported by data relating to the two impurities, Vi5-D5 and Vi3-D3.

This substance has theoretically four geometric isomers. It has not been possible to separate these isomers and no differences in physicochemical properties have been observed.

Vi4-D4is a liquid at ambient temperature and pressure, with a measured melting point of -55.6°C and a predicted boiling point of 220°C. It has a measured density of 0.9875 g/cm3at 20°C, a predicted kinematic viscosity of 6.3 mm2/s at 20°C, and a measured vapour pressure of 93.5 Pa at 25°C. It has a measured auto-ignition temperature of 236°C, and is not explosive and not oxidising on the basis of structural examination.

The substance has a measured log Kowof 6.47 at 20°C and a measured water solubility of 0.0073 – 0.0088 mg/l (7.3 – 8.8 ppb) at 23°C. The substance is not surface active based on structural examination.

In contact with water,Vi4-D4 will hydrolyse moderately quickly with a predicted hydrolysis half-life of approximately 63 h at pH 7 and 20 - 25°C. The half-life is for degradation of the parent substance by ring-opening; full hydrolysis will take longer.The ultimate hydrolysis product is methylvinylsilanediol according to the following equation:

[Si(CH3)(CH=CH2)O]4+ 4H2O→ 4[(CH3)(CH=CH2)Si(OH)2]

The registration substance has an average purity of >80% Vi4-D4, with <15% 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane (Vi5-D5; CAS 17704-22-2; Impurity 1) and <10% 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane (Vi3-D3; CAS 3901-77-7; Impurity 2) present as impurities. The presence of these impurities is not expected to affect the overall hazard profile of the substance based on the available evidence. Predicted vapour pressures of 0.6 Pa and 67 Pa at 25°C, water solubilities of 9.1E-06 mg/l and 1.3E-01 mg/l at 20°C, and log Kowvalues of 9.0 and 6.7 at 20°C were determined for Vi5-D5 and Vi3-D3, respectively. The impurities hydrolyse in a similar manner to Vi4-D4 giving the same ultimate hydrolysis product, methylvinylsilanediol. The half-lives are approximately 1600 h for Vi5-D5 and 0.5 h for Vi3-D3.

The registration substance is not classified as flammable according to EC Regulation 1272/2008, on the basis of a measured flash point (for the registration substance itself) of 88°C and predicted boiling points for Vi4-D4, Vi5-D5 and Vi3-D3 of 220°C, 270°C and 170°C, respectively. The registration substance has a measured auto-ignition temperature of 236°C. It is not explosive and not oxidising on the basis of structural examination.