Heptamethyltrisiloxane

Understanding the Physical Properties of Heptamethyltrisiloxane: A Comprehensive Overview​

Heptamethyltrisiloxane (CAS 1873-88-7), a foundational organosilicon compound, is widely recognized for its unique physicochemical characteristics. This article delves into its key physical properties, supported by experimental data and industrial insights, to provide a holistic understanding of its behavior and applications.

​1. Molecular Composition and Basic Parameters​

Heptamethyltrisiloxane features a molecular formula of ​C₇H₂₂O₂Si₃, with a molecular weight of ​222.5 g/mol​ . Its structure comprises three silicon atoms linked by oxygen bridges and terminated with methyl groups, creating a compact yet flexible framework. This arrangement contributes to its exceptional stability and compatibility with diverse chemical systems.

​2. Physical State and Appearance​

At room temperature, heptamethyltrisiloxane exists as a ​colorless to nearly colorless transparent liquid​ . Its viscosity is relatively low, enabling easy handling in industrial and laboratory settings.

​3. Thermal and Stability Characteristics​

• ​Boiling Point: 142°C (287.6°F) at atmospheric pressure .
• ​Melting Point: Below 0°C, ensuring liquidity across a broad temperature range .
• ​Thermal Decomposition: Thermogravimetric analysis (TGA) reveals initial decomposition at ~523 K (250°C), primarily due to solvent or water loss. The siloxane backbone remains stable up to ~685 K (412°C) .
• ​Hydrolytic Sensitivity: Reacts with aqueous bases but exhibits moderate stability under neutral or acidic conditions .

​4. Solubility and Miscibility​

• ​Organic Solvents: Miscible with chloroform, ethanol, and diethyl ether .
• ​Water: Insoluble, making it ideal for applications requiring phase separation or surface activity .

​5. Surface Tension and Wettability​

Heptamethyltrisiloxane’s hydrophobic siloxane backbone and methyl groups confer ​ultra-low surface tension​ (~20 mN/m), enabling superior wetting and spreading on hydrophobic surfaces . This property is critical in agricultural adjuvants and coatings, where rapid coverage enhances efficacy .

​6. Refractive Index and Optical Properties​

With a refractive index of ​1.382 (at 20°C)​, it is often used in optical applications requiring precise light refraction .

​7. Vapor Pressure and Flammability​

• ​Vapor Pressure: 8.5 hPa (0.085 kPa) at 25°C, indicating moderate volatility .
• ​Flammability: Classified as a flammable liquid (flash point: 27.8°C), necessitating cautious storage .

​8. Industrial Applications Highlighting Physical Traits​

• ​Surface Active Agents: Its low surface tension makes it a key precursor for silicone surfactants, improving emulsification in pesticides and cosmetics .
• ​Polymer Modifications: Acts as a crosslinking agent in silicone-polyether hybrids, enhancing durability in coatings and adhesives .
• ​Analytical Chemistry: Utilized in gas chromatography as a stationary phase for separating high-boiling compounds .

​Why Choose Biyuan for Heptamethyltrisiloxane?​​

Biyuan Chemicals stands out as a trusted supplier of ​high-purity heptamethyltrisiloxane​ (≥99% GC), ensuring consistent performance in critical applications. Our product adheres to stringent quality standards, with rigorous testing for thermal stability, solubility, and reactivity. Whether you’re formulating agricultural additives or advanced coatings, Biyuan’s heptamethyltrisiloxane delivers reliability and efficiency.

Explore our product catalog to learn more about our heptamethyltrisiloxane offerings.

​Conclusion​

Heptamethyltrisiloxane’s unique blend of thermal resilience, surface activity, and chemical versatility makes it indispensable in modern industries. By understanding its physical properties, professionals can optimize formulations for enhanced performance and sustainability. For tailored solutions, partner with Biyuan—a leader in silicon-based chemical innovation.

Note: All data cited are derived from peer-reviewed studies and supplier specifications .