Octadecyltriethoxysilane

Product Overview of Octadecyltriethoxysilane

Chemical Identity

Octadecyltriethoxysilane, designated Siwin-91832, is a long-chain alkyl-functional silane with the molecular formula C24H52O3Si and a molecular weight of 416.75 g/mol. It carries the CAS number 7399-00-0 and the EINECS number 230-995-9. The compound features an 18-carbon straight alkyl chain bonded to a triethoxysilyl group, providing a hydrophobic organic tail with hydrolyzable ethoxy head groups.

Structural Features and Properties

The C18 long alkyl chain imparts significant hydrophobicity and low surface energy characteristics to treated surfaces. The three ethoxy groups hydrolyze in the presence of moisture to form silanol groups, which can condense with hydroxyl groups on inorganic surfaces or with each other to form siloxane bonds. The ethoxy groups hydrolyze at a slower rate than methoxy equivalents, providing longer working time in solution-based applications and more uniform film formation.

Technical Specifications of Octadecyltriethoxysilane

Typical Properties

Additional Technical Parameters

The product has a melting point of approximately 10-12°C and a flash point of approximately 195°C. It is soluble in common organic solvents including toluene, xylene, ethanol, and petroleum ethers, and exhibits low solubility in water. The compound is moisture-sensitive and hydrolyzes gradually under humid conditions. Purity is determined by gas chromatography (GC) analysis. Each batch is accompanied by a Certificate of Analysis detailing all test results.

Industrial Applications of Octadecyltriethoxysilane

Hydrophobic Surface Modification

Siwin-91832 is widely used for hydrophobic surface treatment of various inorganic substrates. When applied to glass, metal, ceramic, or mineral surfaces, it forms a self-assembled monolayer that imparts water-repellent properties. The long C18 alkyl chain creates a low-energy surface that reduces water contact angle hysteresis and provides durable hydrophobic performance. This application is particularly relevant for architectural glass, automotive components, and electronic device protection.

Filler and Pigment Treatment

In polymer composite formulations, Siwin-91832 serves as a surface modifier for inorganic fillers and pigments such as calcium carbonate, talc, silica, and titanium dioxide. The treatment improves hydrophobicity of the filler surface and enhances compatibility with non-polar polymer matrices, especially polyolefins. Better dispersion of treated fillers results in improved mechanical properties, reduced melt viscosity, and enhanced processing characteristics in filled polymer systems.

Chromatography Material Preparation

Siwin-91832 is used in the preparation of reversed-phase C18 chromatographic column packings. Silica gel particles treated with octadecyltriethoxysilane form bonded-phase materials with C18 alkyl chains attached to the silica surface. These C18 stationary phases are the most widely used media in reversed-phase high-performance liquid chromatography (RP-HPLC), providing separation based on hydrophobic interactions between analytes and the alkyl chains.

Protective Coatings

The product is used in the formulation of protective coatings for metal surfaces, including aluminum alloy surface treatment. When applied as a primer or additive, it forms a hydrophobic siloxane network that improves corrosion resistance and water repellency of the coated surface. It also finds use in textile finishing applications where durable water repellent properties are required.

Usage Guidelines for Octadecyltriethoxysilane

Application Methods

For surface treatment applications, Siwin-91832 is typically diluted to concentrations of 1% to 5% by weight in an appropriate solvent system, often with controlled addition of water to initiate hydrolysis. For filler treatment, it can be applied by dry blending or wet treatment methods, with typical dosage levels ranging from 0.3% to 1.5% by weight of the filler, depending on surface area and application requirements.

Handling Considerations

The product should be handled in well-ventilated areas with appropriate personal protective equipment. Containers should be kept tightly sealed when not in use to prevent moisture ingress. The material has a relatively high flash point, but standard precautions for handling flammable chemical liquids should be observed.

Packaging and Quality Assurance for Octadecyltriethoxysilane

Packaging and Storage

Siwin-91832 is available in 190 kg drums and 950 kg IBC containers, with custom packaging options available for commercial procurement orders. The product should be stored in tightly sealed containers at room temperature in a dry, shaded area, away from acids, alkalis, and sources of ignition. Under proper storage conditions, the shelf life is 12 months from the date of manufacture.

Quality Control

Each production batch undergoes standardized quality control testing including GC purity analysis, density measurement, refractive index determination, and visual inspection. The manufacturing process follows established protocols to ensure batch-to-batch consistency. Technical support personnel are available to assist enterprise customers with application development, process optimization, and technical inquiries.

FAQ About Octadecyltriethoxysilane

What is the primary function of octadecyltriethoxysilane in surface treatment?

Octadecyltriethoxysilane forms a hydrophobic siloxane layer on inorganic surfaces through hydrolysis and condensation of its ethoxy groups. The C18 alkyl chain provides low surface energy, resulting in water-repellent properties on treated substrates.

How does octadecyltriethoxysilane compare with octadecyltrimethoxysilane?

The primary difference is the hydrolyzable group: ethoxy vs methoxy. Triethoxy silanes hydrolyze at a slower rate than trimethoxy equivalents, providing longer working time in solution and potentially more uniform film formation. Methoxy versions react faster and may be preferred where rapid curing is required.

What is the recommended dosage for filler surface treatment?

Typical dosage ranges from 0.3% to 1.5% by weight of the filler, depending on the specific filler type, surface area, and application requirements. Optimal loading should be determined through systematic testing measuring dispersion quality and composite mechanical properties.

Can Siwin-91832 be used for C18 chromatography column preparation?

Yes, octadecyltriethoxysilane is used in the preparation of reversed-phase C18 chromatographic stationary phases. The silane bonds to silica gel surfaces, forming a hydrophobic C18 bonded phase suitable for reversed-phase HPLC separations.

What storage conditions are required to maintain product quality?

Store in original, tightly sealed containers in a cool, dry area away from direct sunlight and moisture. The product is moisture-sensitive, so minimizing exposure to humid air is critical. Once opened, use the contents promptly or maintain a dry inert gas blanket in the container.