title: Hydrolysis of polydimethylsiloxane fluids in controlled aqueous solutions.
abstract: Accelerated degradation tests were performed on polydimethylsiloxane (PDMS) fluids in aqueous solutions and in extreme chemical conditions (pH 2-4 and 9-12). Results confirmed that silicones can be degraded by hydrolysis. Higher degradation levels were achieved in very acidic and alkaline conditions. Degradation products are probably polar siloxanols. In alkaline conditions, the counter-ion was found to have a strong influence on degradation level. Degradation kinetic studies (46 days) were also performed at different pH values. Supposing zeroth-order kinetics, degradation rate constants at 24 °C were estimated to 0.28 mgSi L(-1) day(-1) in NaOH solution (pH 12), 0.07 mgSi L(-1) day(-1) in HCl solution (pH 2) and 0.002 mgSi L(-1) day(-1) in demineralised water (pH 6). From these results, the following hypothesis was drawn: PDMS hydrolysis could occur in wastewater treatment plants and in landfill cells. It may be a first step in the formation of volatile organic silicon compounds (VOSiCs, including siloxanes) in biogas: coupled to biodegradation and (self-) condensation of degradation products, it could finally lead to VOSiCs.
authors.affiliation: Université de Lyon, INSA-Lyon, Laboratoire de Génie Civil et d'Ingénierie Environnementale LGCIE, 20 avenue Albert Einstein, F-69621 Villeurbanne, France E-mail: gaelle.ducom@insa-lyon.fr.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Ducom
authors.forename: Baptiste
authors.initials: B
authors.lastname: Laubie
authors.forename: Aurélie
authors.initials: A
authors.lastname: Ohannessian
authors.forename: Claire
authors.initials: C
authors.lastname: Chottier
authors.forename: Patrick
authors.initials: P
authors.lastname: Germain
authors.forename: Vincent
authors.initials: V
authors.lastname: Chatain
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D014867:Water / Q000737:chemistry*
chemical_list: D004129:Dimethylpolysiloxanes; D014867:Water; C013830:baysilon