Registration Dossier
Registration Dossier
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EC number: 219-842-7 | CAS number: 2550-02-9
Endpoint summary
Administrative data
Description of key information
Additional information
- Concentration of the silanol; the greater the initial concentration, the greater the degree of condensation. Significant condensation is not expected at concentrations less than approximately 100 mg/l, but is dependent on specific conditions
- pH; the condensation reaction may be either acid or base catalysed
- Temperature
- Other species present
- Timescale
- The nature of the R group
- The number of Si-OH groups; silanetriols condense more rapidly than silanediols
Physico-chemical properties
Triethoxypropylsilane is a liquid at ambient temperature and pressure, with a measured melting point of < -100°C and a measured boiling point of 175°C. It has a measured density of 0.89 g/cm³ at 20°C, a predicted viscosity of 1.3 mm²/s at 20°C and a predicted vapour pressure of 13 Pa at 25°C. The substance is moderately soluble in water based on a predicted water solubility of 280 mg/l; it has a measured log Kow of 3.1.
The substance is classified as flammable on the basis of a measured flash point of 58.5 °C. It has a measured auto-ignition temperature of 225°C at 1022.1 hPa and is not explosive and not oxidising on the basis of chemical structure.
In contact with water triethoxypropylsilane reacts (measured half-life of 1.4 days at pH 7 and 20°C) to produce propylsilanetriol and ethanol according to the following equation:
C3H7Si(OC2H5)3 + 3 H2O → C3H7Si(OH)3 + 3 C2H5OH
Ethanol is miscible with water, has low log Kow (-0.3) and high vapour pressure (7910 Pa at 25°C). The hydrolysis product, propylsilanetriol is predicted to be very soluble with water at 20oC and has low log Kow (-1.4, predicted) and is less volatile than the parent substance (vapour pressure = 4.6 x 10-3 Pa at 25°C, predicted). It is not expected to undergo significant dissociation in an environmentally-relevant range.
Silanetriols may undergo condensation reactions to give siloxane dimers, oligomers and polymers, according to the scheme:
RSi(OH)3 ⇄ RSi(OH)2OSi(OH)2R ⇄ RSi(OH)2O[Si(R)(OH)O]nSi(OH)2R
(where R is an alkyl or aryl side-chain)
A highly cross-linked gel may form. The degree of condensation that will occur may vary with:
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