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The registration substance is a reaction mass of two constituents, Constituent 1: 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane (CAS 17704-22-2; Vi5-D5)and Constituent 2: 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (CAS 2554-06-5; Vi4-D4).

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

Reaction Mass of 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane is a liquid at ambient temperature and pressure, with a melting point of <-80°C at 1013 hPa (OECD 102), a boiling point range of 216.6 -226.5°C at 1009 ± 1 hPa (OECD 103) and a density of 0.988 g/cm3 at 20°C (OECD 109). The substance has a flash point value of 87.5°C at 1013 hPa and an auto-ignition temperature of 259.0°C; it is not explosive and not oxidising on the basis of structural examination. The substance is not surface active based on structural examination.

No measured data are available for the substance as a whole for vapour pressure, water solubility or log Kow. Constituent 2 of the registration substance (Vi4-D4) has a measured vapour pressure of 93.5 Pa at 25°C, a measured log Kow of 6.47 at 20 -25°C and a measured water solubility of 0.0073 – 0.0088 mg/l (7.3 – 8.8 ppb) at 23°C. Constituent 1 (Vi5-D5) has a predicted vapour pressure of 67 Pa at 25°C, a predicted log Kow of 9.0 at 20 -25°C and a predicted water solubility of 9.1E-06 mg/l at 20°C. Constituent 1 is not manufactured as an isolated product and it is therefore not possible to obtain measured values for this Constituent.

In contact with water, the registration substance will hydrolyse moderately quickly with a predicted hydrolysis half-life of >63 h at pH 7 and 20 - 25°C. The half-life is for degradation by ring-opening; full hydrolysis will take longer. The ultimate hydrolysis product of both constituents of the registration substance is methylvinylsilanediol.

The registration substance is not classified as flammable according to EC Regulation 1272/2008, on the basis of a measured flash point of 87.5°C and a measured boiling range of 216.6 - 226.5°C at 1009 ± 1 hPa. The registration substance has a measured auto-ignition temperature of 259.0°C. It is not explosive and not oxidising on the basis of structural examination.