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The major and minor linear constituents of the substance are hydrolytically unstable with half-lives for siloxane degradation of 630 – >63 000 h at pH 7 and 20-25°C. The minor cyclic constituents of the substance are also expected to be hydrolytically unstable. Hydrolysis half-lives for the ring-opening step are read-across from the structurally analogous methyl-substituted cyclic siloxane, and range from 0.4 - >10,000 h. Subsequent hydrolysis half-lives of the ring-opened structure are predicted to be of ≥10,000 h at pH 7 and 20-25°C. The ultimate hydrolysis products of the reaction are phenylsilanetriol and trimethylsilanol. Therefore, the environmental hazard assessment is based on the properties of the parent substance in accordance with REACH guidance for Chemical Safety Assessment (Chapter R.16; ECHA, 2016).

Trimethylsilanol and phenylsilanetriol are the final products of hydrolysis reactions under the normal range of conditions of pH and temperature. However, other biotic or abiotic reactions may proceed over longer time-scales in the environment.