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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Physico-chemical properties

[3-(trimethoxysilyl)propyl]urea is a liquid at standard temperature and pressure, with a measured melting point of -23 °C and a predicted boiling point of 284 °C. It has a predicted density of 1.04 g/cm³ at 20 °C and a predicted vapour pressure of 2.8E-02 Pa at 25 °C.

The substance is not classified as flammable on the basis of a measured flash point of 110 °C and the high boiling point. It has a measured auto-ignition temperature of 375°C, and is not explosive and not oxidising on the basis of chemical structure.

In contact with water [3-(trihydroxysilyl)propyl]urea is predicted to react (half-life 2.8 hours at RT and pH 7) to produce [3-(trimethoxysilyl)propyl]urea and methanol according to the following equation:


(CH3O)3SiCH2CH2CH2NHC(=O)NH2 + 3H2O ¿ (HO)3SiCH2CH2CH2NHC(=O)NH2 + 3CH3(OH)


Therefore the properties of the silanol hydrolysis product, [3-(trimethoxysilyl)propyl]urea are assessed instead. The hydrolysis product is very soluble in water, 1.0E+06 mg/l (predicted), with a log Kow of -3.3 (predicted). It is not considered to be surface active. The hydrolysis product is less volatile than the parent substance (vapour pressure = 4.1E-07 Pa at 25 °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

Additional information