Polysorbate 81 (Tween 81) – Low-EO Oleate Surfactant

Overview

Chemical Nature

Polyoxyethylene (5) Sorbitan Monooleate. Contains reduced Ethylene Oxide (5 moles) compared to Tween 80.
Appearance & Specs

Amber oily liquid | HLB Value: 10.0
★ Primary Application (Industrial)

Powerful Coupling Agent. Unique intermediate HLB bridges the gap between oil and water phases. Solves separation issues in difficult formulations.
Lubricity & Stability

Excellent lubricity and stability in mineral oils and solvents.
Key Functions

Coupling Agent & Emulsifier.

Molecular Structure

Structural Components

Hydrophilic Segment: Polyoxyethylene chain introduced by ethoxylation. Note the reduced chain length (5 moles as indicated by formula) compared to standard Tween 80.

Hydrophobic Moiety: Oleic acid residue derived from unsaturated fatty acid, providing significant oil solubility.

Backbone: Sorbitan backbone linking the hydrophilic and hydrophobic segments.
★ Mechanism of Action

Bridging Capability. The lower degree of ethoxylation creates a unique intermediate HLB. This allows the molecule to function as a powerful coupling agent, effectively bridging the gap between oil and water phases in formulations where standard high-HLB emulsifiers fail.

Specifications:

Polysorbate 81 usually appears as a viscous liquid with good water solubility. Due to its relatively high ethoxylation level, it exhibits superior hydrophilicity. In formulations, it significantly enhances the stability of oil-in-water emulsions. When combined with other emulsifiers such as sorbitan esters, it enables optimization of emulsification performance.

Test Parameter	Unit	Minimum	Maximum
HLB value	——	10.0
Saponification Value	mgKOH/g	95	105
Hydroxyl Value	mgKOH/g	135	165
Acid Value	mgKOH/g	-	2
Moisture Content	%	-	3
HLB	——	15.0

Download TDS

Applications:

Metalworking Fluids (Cutting Oils):Used to emulsify mineral oils in water for cooling and lubricating metal cutting machinery.
Textile & Leather Auxiliaries: Acts as an antistatic agent and fiber lubricant, helping threads pass through machines smoothly without breaking.
Industrial Cleaning Solvents: Emulsifies heavy greases and solvents, allowing them to be rinsed away with water.
Agrochemicals: Used in oil-based pesticide concentrates (EC formulations) to improve emulsion stability upon dilution.

Intermediate HLB (10.0) Balance

Perfectly positioned between lipophilic Spans and hydrophilic Tweens. It effectively stabilizes emulsions that are too oily for standard Tween 80 to handle.

Superior Mineral Oil Solubility

Due to its lower EO content (5 moles), it dissolves much more easily in mineral oils and solvents than Tween 80, making it ideal for oil-based concentrates.

High Lubricity (Oleic Source)

Derived from Oleic Acid, it provides excellent surface lubrication, reducing friction in metal processing and textile fiber manufacturing.

Low-Foaming Profile

Generates significantly less foam than high-EO surfactants (like Tween 20/80), suitable for high-speed industrial agitation processes.

Milky white metalworking cutting fluid emulsion stabilized by Polysorbate 81, cooling a metal lathe.

Textile fibers running smoothly through machinery, demonstrating the antistatic and lubricating properties of Tween 81

Laboratory demonstration of Polysorbate 81 acting as a coupling agent to successfully mix oil and water phases.

storage & package:

Storage:
Store in a cool, dry, and well-ventilated area, away from direct sunlight and sources of heat.
Avoid contact with harmful or incompatible substances. Handle with care during transportation to prevent leakage or contamination.

Transportation:
Transport as a general chemical product, following standard safety and handling procedures.

Package:
Polysorbate 81 is packed in high-quality PE drums with double-seal lids.
Standard packaging sizes include 25kg/drum, 200kg/drum, and 1000kg IBC tote to meet different usage needs.