Tween (polysorbate series) is typically an amber to yellow viscous liquid, paste, or waxy solid at room temperature (the specific form depends on the fatty acid type and the degree of ethoxylation). It is readily soluble in water and various organic solvents. As a non-ionic surfactant obtained by ethoxylation modification of Span, its chemical properties are stable, with resistance to acids, alkalis, and hard water. However, due to the presence of ester bonds, hydrolysis may still occur under strong acidic, strongly alkaline, or high-temperature conditions. The introduction of a large number of hydrophilic polyoxyethylene chains into its molecule results in extremely strong hydrophilicity, classifying it as a water-soluble emulsifier with a high Hydrophile-Lipophile Balance (HLB) value. Based on its excellent emulsifying, dispersing, solubilizing, and stabilizing properties, the primary application of Tween is as a hydrophilic base emulsifier and solubilizer. It is widely used in food (e.g., beverages, ice cream), cosmetics (e.g., lotions, creams), pharmaceuticals (e.g., vaccine adjuvants, oral solutions), and industrial fields (e.g., pesticide emulsification, textile finishing). It is particularly commonly used in combination with the lipophilic Span series in specific ratios to construct emulsification systems with optimal stability.