Tween T-81 (Polysorbate 81, CAS No.: 9005-65-6) is a high molecular weight compound produced from sorbitol, oleic acid, and ethylene oxide through a series of chemical reactions. Its molecular structure is based on a sorbitan core, with a monooleate hydrophobic chain introduced via esterification, followed by ethoxylation to graft approximately 5 polyoxyethylene (EO) hydrophilic units, forming an amphiphilic "hydrophilic head - lipophilic tail" molecular structure. This structure endows Tween T-81 with excellent surface activity, allowing it to align at the oil-water interface and significantly reduce interfacial tension.
As a nonionic surfactant, Tween T-81 does not ionize in aqueous solutions, thus exhibiting excellent chemical stability — it remains active over a wide pH range, tolerates acids, alkalis, and hard water, and does not readily react with other electrolytes. Its appearance is amber oily liquid, classified as a water-in-oil (W/O) type emulsifier, performing multiple functions such as emulsification, solubilization, wetting, and dispersion in various industries including cosmetics, food, pharmaceuticals, pesticides, and coatings.
| Item | Parameter Information |
|---|---|
| Chemical Name | Polyoxyethylene (5) Sorbitan Monooleate |
| INCI Name | PEG-5 Sorbitan Monooleate |
| Synonyms | Polysorbate 81, Tween 81, POE (5) Sorbitan Monooleate |
| CAS No. | 9005-65-6 |
| Product Type | Nonionic Surfactant |
| Appearance | Amber Oily Liquid |
| EO Moles | Approximately 5 moles |
| Emulsion Type | Water-in-Oil (W/O) Type |
| Molecular Structure Components | Sorbitol (core) + Oleic Acid (hydrophobic chain) + Polyoxyethylene chain (hydrophilic group) |
Tween T-81 is often used in combination with Span series (e.g., Span 80, Span 85). By adjusting their ratio, the hydrophilic-lipophilic balance (HLB) value of the system can be flexibly controlled to achieve more precise emulsification effects. It is used as an emulsion stabilizer in the food industry for products like ice cream and margarine; in cosmetics for creams, lotions, and makeup remover formulations; and in pesticide formulations for preparing emulsifiable concentrates, microemulsions, and emulsion concentrates.