The molecular structure of silicone oil lays the foundation for its softness. The main chain of silicone oil (polysiloxane) is composed of silicon-oxygen (Si-O) bonds. These bonds are relatively long and have large bond angles, giving the molecular chain excellent flexibility. Simultaneously, the side chain groups (such as methyl and amino groups) in the silicone oil molecule can rotate freely, making the molecular chain highly flexible in space. When silicone oil adheres to the fiber surface, its molecular chains can freely adjust their conformation according to the bending and friction of the fiber, forming a smooth lubricating film. This significantly reduces the coefficient of friction between fibers, providing a soft touch to the fabric at a microscopic level.

The interaction between silicone oil and fibers enhances the softness effect. The side chain groups (such as amino groups) in the silicone oil molecule can combine with functional groups such as hydroxyl and carboxyl groups on the fiber surface through hydrogen bonds or chemical bonds, forming a directional adsorption layer. This adsorption not only allows the silicone oil to adhere firmly to the fiber surface but also fills the tiny pits on the fiber surface through the arrangement of the molecular chains, making the fiber surface smoother. For example, cotton fabrics treated with amino-modified silicone oil can have their bending stiffness reduced by 40%-60% and their coefficient of friction lowered to below 0.1, achieving a silk-like softness.

The multifunctionality of silicone oil expands the application scenarios of fabric softeners. Silicone oil not only provides softness but can also impart other functions to fabrics through chemical modification. For example, polyether-modified silicone oil can improve the moisture absorption of fabrics, epoxy-modified silicone oil can enhance the wrinkle resistance of fabrics, and fluorinated silicone oil can impart waterproof and stain-resistant properties to fabrics. This "one agent, multiple effects" characteristic makes silicone oil a core auxiliary agent in the finishing of high-end textiles, widely used in sportswear, infant clothing, and other fields.