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Environmental fate & pathways

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2,4,6,8-Tetramethylcyclotetrasiloxane hydrolyses rapidly. The half-life for the initial ring-opening has been determined to be 2.2 min (0.037 h) at pH 7 and 22.5oC. This gives a half-life of ca. 0.085 h at pH 7 and 12oC using the conversion DT50 (XoC) = DT50 (t) x e(0.08(T-X))(ECHA Guidance R16). The rate constant, k, is then ln2 / 0.085 = 8.2 h-1.