For procurement managers, R&D scientists, and formulation chemists in industries requiring high-vacuum environments, a thorough understanding of material specifications is critical. Pentaphenyl Trimethyl Trisiloxane, a pivotal phenyl silicone fluid often utilized in diffusion pumps and vacuum coatings, possesses a unique set of technical properties that dictate its performance. This deep dive explores these specifications, helping professionals make informed purchasing decisions.

The chemical name, 1,1,3,5,5-pentaphenyl-1,3,5-trimethyltrisiloxane, and its CAS number 3390-61-2, uniquely identify this compound. Its molecular formula, C33H34O2Si3, corresponds to a molecular weight of approximately 546.88 g/mol, indicating a complex structure that contributes to its specialized characteristics.

Key Physical and Chemical Properties:

• Appearance: Typically described as colorless to straw-colored liquid. This visual consistency is an initial indicator of product purity.
• Density: Approximately 1.09 g/cm³ at 25°C. This value is important for volume-to-mass calculations and system design where fluid weight is a consideration.
• Melting Point: Around -25°C, indicating it remains liquid in most operational temperatures. Some sources note a congealing point between -14°C to -18°C.
• Boiling Point: At 0.06 torr, the boiling point is approximately 242°C. This highlights its low volatility, a crucial trait for vacuum applications.
• Flash Point: A significant safety parameter, the flash point (open cup) is typically ≥243°C. This high flash point ensures operational safety by minimizing the risk of ignition at elevated temperatures.
• Viscosity: This property is critical for flow dynamics within pumps. At 25°C, the kinematic viscosity is commonly in the range of 160-190 cSt (or mm²/s), with values around 170-175 cSt frequently cited. Viscosity at 40°C is typically around 61-64 cSt.
• Refractive Index: Measured at 25°C, it is usually between 1.5765 and 1.5785. This property can be useful for quality control and identification.
• Ultimate Vacuum: When used in diffusion pumps, it can achieve ultimate vacuum levels of 5x(10-9 ~ 10-10) torr (untrapped), demonstrating its effectiveness in creating ultra-high vacuum environments.
• Saturated Vapor Pressure: Exceptionally low, often cited as 5x10-10 torr, which is fundamental to its performance in vacuum systems.

For professionals looking to buy Pentaphenyl Trimethyl Trisiloxane, these specifications are not just data points but crucial indicators of a product's suitability for specific tasks. Manufacturers in China are adept at providing this information, along with certifications that attest to the purity (≥99.0%) and consistency of their product. When sourcing, always request a Certificate of Analysis (CoA) that details these key parameters. Understanding these technical aspects empowers you to select the most appropriate supplier and ensure optimal performance from your vacuum equipment.