Dimethyl silicone oil, with the chemical name polydimethylsiloxane, is a colorless transparent, viscous liquid. It is formed by direct polymerization of monomers and has an extremely high purity. It possesses excellent hydrophobicity, high-temperature resistance, chemical inertness, and electrical insulation properties. It is a fundamental material for many high-performance applications and is commonly used in high-temperature lubricants, electronic component insulation, advanced cosmetic additives, and defoamer concentrate solutions, etc., where high-temperature stability, high insulation, precise lubrication, or as a chemical intermediate are required. 
The dimethyl silicone oil emulsion is a stable milky white liquid formed by uniformly dispersing silicone oil in water under the action of emulsifiers and mechanical force. Besides silicone oil, it also contains water, emulsifiers and other components. This transformation in form fundamentally changes its properties, turning it into an oil-in-water system, which can be directly diluted with water, making it convenient for handling and application. It is particularly suitable for water-based systems. It focuses on leveraging the soft, smooth and hydrophobic surface properties of silicone oil, while also endowing the system with hydrophilicity, facilitating its penetration and uniform adhesion to porous materials such as fibers and leather. It is widely used in the softening of textiles, the smooth treatment of leather, the conditioning agent for daily care products, the papermaking defoaming process, and the agricultural defoaming field. 
In summary, dimethyl silicone oil is the fundamental performance factor, and the dimethyl silicone oil emulsion is its practical and functional form adapted to the aqueous environment. The choice of form depends on the specific requirements of the final application for performance, process convenience, and cost balance.