The chemical structure of ethyl silicone oil (polydiethylsiloxane) is based on a silane-oxygen bond (—Si—O—) as the backbone, with ethyl (—C₂H₅) groups as side chains. Its molecular formula is C₄ₙ₊₁₂H₃₀₊₁₀nSiₙ₊₂Oₙ₊₁, and its CAS number is 63148-61-8.

Key Properties
Molecular Flexibility: The long silane-oxygen bond length (approximately 1.64 Å) and large bond angle (approximately 130°) impart high flexibility to the molecular chain, allowing it to maintain fluidity even at low temperatures (freezing point < -70°C).

Low Surface Tension: The hydrophobic nature of the ethyl side chains results in extremely low surface tension (approximately 20-21 mN/m), providing excellent lubricity and anti-adhesion properties.

Temperature Resistance: Long-term operating temperature range -70°C to 150°C, flash point >265°C (open cup), and superior high-temperature stability to methyl silicone oil.

Chemical Inertness: The ethyl substituent enhances compatibility with mineral oils while maintaining oxidation and corrosion resistance.

Molecular Rearrangement and Synthesis: Prepared by co-hydrolysis and condensation of diethyldiethoxysilane and triethylethoxysilane, followed by catalytic equilibrium, molecular rearrangement technology allows for controllable viscosity (8-1000 mm²/s). Its refractive index (1.438) and density (0.95-1.05 g/cm³) contrast well with phenyl silicone oils, making it suitable for precision lubrication and electrical insulation.