Phenyltriethoxysilane, with the molecular formula C12H20O3Si and a molecular weight of about 240.38 g/mol, stands as a significant organosilicon compound used in a range of chemical manufacturing and industrial processes. Identified by the CAS number 780-69-8 and classified with the HS Code 2931.90.0090, this material carries a distinct combination of phenyl and triethoxysilyl functional groups, which introduces flexibility and adaptability in coatings, surface modifications, and crosslinking reactions. The structure contains a silicon atom bonded to a phenyl group and three ethoxy groups, which influence both its reactivity and solubility.
In practical terms, Phenyltriethoxysilane most frequently appears as a colorless to pale yellow liquid, though under certain environmental or storage conditions, one might notice a mild crystallization or precipitation, forming solid or flake-like material. The compound gives off a faint aromatic odor, a byproduct of its phenyl group. It possesses a specific gravity ranging from approximately 1.056 to 1.080 g/cm3 at 25°C. Thanks to the triethoxy end, the product dissolves well in most organic solvents, including alcohols, ethers, and aromatic hydrocarbons; however, it resists significant solubility in water, where it can undergo slow hydrolysis. The boiling point sits between 288°C and 292°C, and the material typically flows easily due to its low viscosity, making handling straightforward in large-scale processes or laboratory settings. No matter if it's stored in drum, IBC, or as small samples in glass, the bulk properties remain stable as long as the package stays sealed tightly and moisture remains out of the way.
The key aspect of Phenyltriethoxysilane chemistry comes from how its ethoxy groups react with water, acids, or basic catalysts. These reactions produce silanols, which then readily condense with themselves or with surface hydroxyls on materials like glass, metals, minerals, or ceramics. This makes the molecule an effective coupling agent or surface modifier, boosting adhesion between organic polymers and inorganic surfaces. The phenyl group provides heat resistance and unique compatibility with aromatic resins or matrix materials. At the bench, it stands up well to neutral conditions but will slowly break down in the presence of moisture, which makes humidity control in storage and handling a practical concern. Experienced users keep small volumes tightly capped or use nitrogen blanketing during larger transfers to minimize hydrolysis and maintain purity.
On a typical analysis, you will see purity listed above 98% (GC); sometimes, technical grades run slightly lower depending on use case or batch processing route. Residual ethanol content, acidity (as acetic acid), and water content get close attention since those control downstream reactivity. The material flows at ambient temperature, with a flash point usually measured above 120°C (open cup), minimizing immediate flammability risk in routine handling. In powder or pearl form—less common, but still present for specific applications—small, free-flowing white to off-white beads can appear, mostly resulting from controlled solidification techniques. Here, the density approaches that of the liquid, though application choices may shift as dissolving the solid for use can require extra energy input.
From personal experience in the specialty coatings industry, Phenyltriethoxysilane adds reliable performance as a silane coupling agent and adhesion promoter in silicon-based sealants, advanced hybrid adhesives, and filled plastics. Coating manufacturers use the raw material to treat glass beads or mineral fillers before their introduction into resin systems, where the phenyl group helps absorb stress and buffer thermal expansion. In high-performance paints and corrosion-resistant primers, it enhances weathering resistance, lifts gloss retention, and improves the physical interface between coatings and metal or ceramic surfaces. Users working on electronics or optics benefit from its low impurity profile, as even trace water or acidic content may lead to premature gelling or mistimed crosslinking. The molecular structure’s design gives formulators the ability to tune surface energy and hydrophobicity in treated substrates, which proves valuable in applications like anti-graffiti films and water-repellent building materials.
Phenyltriethoxysilane deserves close attention as a hazardous chemical, especially where skin contact, inhalation of vapors, or splashes to the eyes pose risks. Proper engineering controls—chemical fume hoods, splash-proof goggles, nitrile gloves, and closed handling systems—address these concerns head-on. The liquid can irritate respiratory mucosa, with the risk heightened under poorly ventilated storage or use. Short-term skin exposure rarely leads to systemic effects, but repeated unprotected handling can produce dermatitis or burning, particularly in the presence of moisture, given slow hydrolysis to acidic fragments like ethanol and silicic acid. Waste treatment relies on controlled incineration and separation from aqueous waste streams, since accidental release into the environment can harm aquatic life through organic solvent and hydrolysis byproducts.
Access to high-quality Phenyltriethoxysilane relies on most suppliers focusing on batch-to-batch consistency, technical documentation, and robust impurity control. Labs and factories, especially those pursuing ISO or REACH-compliant certifications, check each incoming drum for identity and quality on receipt, frequently confirming GC purity, organosilicon content, and storage temperature logs. As a niche specialty chemical, price and lead time can fluctuate, particularly when feedstock shortages or unexpected regulatory controls emerge in major producing regions. The raw material often ships from bulk chemical manufacturers in Asia, North America, and parts of Europe, each carrying region-specific labeling and transportation documentation to ensure legal transport and product traceability.
From years working alongside technical chemists and production managers, it becomes clear that the benefits Phenyltriethoxysilane delivers—durability, chemical compatibility, crosslinking strength—come with real responsibility. Every step in storage, handing, and disposal requires respect for its toxicological and environmental profile. Yet, through careful process control, full transparency on certificate of analysis, and direct user education, the chemical keeps finding new roles in sustainable coatings, safer plastics, and advanced material science. As a material linking organic and inorganic worlds, it rewards thoughtful stewardship with versatility that few specialty silanes can match.
