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Physical & Chemical properties

Endpoint summary

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Additional information

Physicochemical properties

 

Methyl-N-[3-(trimethoxysilyl)propyl]carbamate is a liquid at standard temperature and pressure. The melting point is <-50°C and the boiling point is 258°C. It has a predicted density of 1.03 g/cm3 at 20°C, a predicted vapour pressure of 0.06 Pa at 20°C and a viscosity of 2.9  mm2/s.

 

The substance is classified as a non-flammable liquid on the basis of the boiling point and a measured flash point of 99°C. It is not pyrophoric or flammable in contact with water. It has a measured self-ignition temperature of 385°C, and is not explosive and not oxidising on the basis of chemical structure. It is not surface active.

 

The substance has a two-step hydrolysis. The rate of formation of the first hydrolysis product, methyl-N-[3-(trihydroxysilyl)propyl]carbamate is relatively fast (half-life 3hours at room temperature and pH 7. However, the rate of formation of the ultimate hydrolysis products, (3-aminopropyl)silanetriol plus methanol and CO2, is extremely slow. Hydrolysis rates (half-life, 25°C, pH 7) of carbamates is reported to vary from a few seconds to 105 years. Therefore only the properties of the first hydrolysis product are described in this summary.

 

(CH3O)3SiCH2CH2CH2N(C=O)OCH3 + 3H2O   (HO)3SiCH2CH2CH2N(C=O)OCH3   + 3CH3OH

 

The silanol hydrolysis product is predicted to be very soluble in water at 20-25°C (1E+06 mg/l) and has a predicted log Kow of -2.3. It is less volatile than the parent substance with a vapour pressure of 9.94E-06 at 25°C (predicted).

 

Methanol is miscible with water, has low log Kow (-0.82 to -0.64) and high vapour pressure, 12.790 Pa at 20°C.

 

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:

 

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.  

The nature of the R group

The number of Si-OH groups; silanetriols condense more rapidly than silanediols.