Methyltriethoxysilane

Methyltriethoxysilane (MTES) is an alkoxysilane used in sol-gel systems, hydrophobization of mineral materials, surface modification, and adhesion improvement in composite and coating systems. The product is a clear, colorless liquid that is sensitive to moisture and capable of hydrolysis followed by the formation of siloxane bonds.

Description

Methyltriethoxysilane is a reactive alkoxysilane used in sol-gel technologies, for surface modification of inorganic materials, hydrophobization of fillers, pigments, and mineral surfaces, and also as an adhesion promoter in polymer and composite systems.

Chemically, the product contains three ethoxy groups capable of hydrolysis and subsequent condensation, resulting in the formation of Si–O–Si siloxane bonds. The methyl group attached to the silicon atom does not hydrolyze and provides treated materials with more pronounced hydrophobic properties.

Purpose

Methyltriethoxysilane is suitable for use in:

• sol-gel systems;
• surface modification of inorganic fillers;
• hydrophobization of mineral materials;
• improving adhesion of organic polymers to inorganic surfaces;
• composite materials;
• functional coatings;
• systems requiring the formation of an organic-inorganic network.

Applications

The product can be used in:

• production of sol-gel compositions;
• paint, coating, and protective systems;
• manufacturing of composites;
• treatment of pigments and fillers;
• materials where reduced water absorption is required;
• technologies where adhesion and hydrophobic properties are important.

Main Properties

• clear, colorless liquid;
• low viscosity;
• high reactivity;
• high hydrolytic sensitivity;
• good solubility in organic solvents;
• hydrolyzes upon contact with water.

How Methyltriethoxysilane Works

The three ethoxy groups in MTES can hydrolyze to form silanol groups, which then undergo condensation to form a three-dimensional siloxane structure. This is why methyltriethoxysilane is used as a functional silane component in sol-gel systems and in surface treatment applications.

The reaction rate depends on pH, temperature, catalyst, and process conditions.

Important Note on Water and Moisture

Methyltriethoxysilane is moisture-sensitive. Upon contact with water, it does not simply dissolve but undergoes hydrolysis. Therefore, when working with the product, the following are important:

• dry storage conditions;
• airtight containers;
• moisture control during use;
• proper selection of solvent and catalyst for the specific process.

Main Technical Characteristics

• Chemical formula: (CH3CH2O)3Si-CH3
• Empirical formula: C7H18O3Si
• CAS: 2031-67-6
• Molecular weight: 178.30 g/mol
• Appearance: clear, colorless liquid
• Density at 20°C: 0.895–0.90 g/cm³
• Boiling point: 140–143°C
• Melting point: below -40°C
• Refractive index nD20: 1.383
• Viscosity at 25°C: about 0.8 mm²/s
• Solubility in water: practically insoluble, hydrolyzes
• Solubility in organic solvents: good
• Purity: above 98–99%
• Hydrolytic sensitivity: high

Advantages

• suitable for sol-gel technologies;
• can be used for forming siloxane structures;
• provides hydrophobic properties to materials;
• useful for modifying the surface of fillers and pigments;
• can improve adhesion in organic-inorganic systems;
• combines alkoxysilane reactivity with a hydrophobic methyl group.

Precautions

Methyltriethoxysilane should not be described as a simple solvent or a neutral additive. It is a reactive silane that is sensitive to moisture. For proper use, the following should be taken into account:

• reaction with water and atmospheric moisture;
• possible change in properties if stored improperly;
• the need for process-specific selection of hydrolysis and condensation conditions;
• the need to follow proper handling rules for organosilane products.

Storage

The product should preferably be stored:

• in tightly closed containers;
• in a dry place;
• with minimal contact with moisture;
• away from conditions where the product or packaging may become wet.

Who This Product Is Suitable For

Methyltriethoxysilane is suitable for companies and technologists working with:

• sol-gel systems;
• hydrophobization of mineral surfaces;
• fillers and pigments;
• composite materials;
• coatings;
• silane surface modifiers;
• systems where improved adhesion between organic and inorganic phases is required.

Conclusion

Methyltriethoxysilane (MTES) is a reactive alkoxysilane for sol-gel technologies, surface modification, hydrophobization, and adhesion improvement in composite and coating systems. Its key features are three hydrolyzable ethoxy groups, a hydrophobic methyl group, and high sensitivity to moisture. These properties make the product suitable for forming siloxane structures and for functional modification of materials.