Ethyl silicone oil (ethyl siloxane fluid), chemically known as polydiethylsiloxane, is an important organosilicon material with unique physicochemical properties. Its volatility and vapor pressure characteristics will be analyzed in detail below from multiple aspects.

Basic Chemical Properties of Ethyl Silicone Oil
Ethyl silicone oil, CAS number 63148-61-8, with the molecular formula C4n+12H3O+10nSin+2On+1, is a pale yellow liquid. Its main physical properties include:

Melting point: <-40°C
Boiling point: >205°C
Density: 0.96 g/cm³
Flash point: 80°C
Refractive index: 1.438
Form: Liquid

Ethyl silicone oil is characterized by low viscosity change with temperature, low freezing point, high temperature resistance, oxidation resistance, water resistance, good dielectric properties, and good lubrication.

Volatility Characteristics of Ethyl Silicone Oil
Ethyl silicone oil exhibits low volatility, specifically characterized by:
Low vapor pressure and low volatility
Volatile content (150℃, 3h) ≤ 1.0 wt%
High compressibility and low surface tension

Non-corrosive to metals
These properties make ethyl silicone oil excellent for applications requiring stability, such as high-temperature environments or long-term use.

Vapor Pressure Data of Ethyl Silicone Oil
The vapor pressure characteristics of ethyl silicone oil are as follows:
Vapor pressure: < 5 mmHg
Vapor pressure at 25℃: 15.5 ± 0.2 mmHg (for ethyltrimethoxysilane)

The low vapor pressure is one of the main reasons for the low volatility of ethyl silicone oil, giving it an advantage in applications requiring low volatility.

The volatility and vapor pressure of ethyl silicone oil are affected by several factors:
Molecular structure: Silicone oils with stronger intermolecular forces have lower saturated vapor pressures. The stability of the silicon-oxygen bond and the length of the ethyl side chain in ethyl silicone oil molecules both affect its intermolecular forces.

Temperature: As temperature increases, the average kinetic energy of silicone oil molecules increases, leading to a rise in saturated vapor pressure. This explains the increased volatility of ethyl silicone oil at high temperatures.

Purity: The presence of impurities affects the saturated vapor pressure of silicone oil; higher purity results in more stable vapor pressure.

External Pressure: Pressure changes also have a certain impact on saturated vapor pressure.
Molecular Weight: The larger the molecular weight, the lower the vinyl content, and generally, the lower the volatility.
Applications and Precautions
Due to its low volatility and vapor pressure, ethyl silicone oil is widely used in the following fields:

Lubricants for high-temperature environments
Insulating materials for electronic components
Stabilizers in cosmetics
Coating materials for medical devices

Precautions for use:
Although it has low volatility, potential volatilization loss should still be considered at high temperatures.
Avoid high temperatures and direct sunlight during storage.

The volatility characteristics of ethyl silicone oils with different molecular weights may vary; the appropriate specification should be selected based on the specific application.

In summary, ethyl silicone oil's low volatility and vapor pressure make it excellent in a variety of industrial applications, especially where stability and high-temperature resistance are required.