For formulation engineers in the food, cosmetic, and industrial sectors, the stability of an emulsion relies heavily on the precise selection of surfactants. Sorbitan esters, commercially known as the Span series, are the cornerstone of non-ionic surfactant chemistry.
Their dominance stems from a unique combination of tunable Hydrophilic-Lipophilic Balance (HLB), chemical stability, and cost-effectiveness. This guide provides a comprehensive technical breakdown—from HLB calculations and solubility profiles to real-world industrial applications—to help you optimize your formulations.
1. The HLB Scale: The Science of Selection
At the core of surfactant selection is the HLB scale (Hydrophile-Lipophile Balance). While modern science has evolved, the HLB system remains the industry standard for predicting whether a surfactant will stabilize a Water-in-Oil (W/O) or Oil-in-Water (O/W) emulsion.
Understanding Span HLB Values
Sorbitan esters are lipophilic (oil-loving) by nature, generally occupying the lower end of the HLB scale (1.8 – 8.6).
| Product | Nom chimique | Valeur HLB | Fonction principale |
| Span 20 | Monolaurate de sorbitane | 8.6 | Wetting agent, O/W co-emulsifier |
| Span 40 | Monopalmitate de sorbitane | 6.7 | Structure builder, W/O emulsifier |
| Span 60 | Monostéarate de sorbitane | 4.7 | Aeration agent, primary W/O emulsifier |
| Portée 80 | Monooléate de sorbitane | 4.3 | Liquid W/O emulsifier, pigment dispersant |
| Span 85 | trioléate de sorbitane | 1.8 | Auxillary emulsifier for high-oil systems |
- Low HLB (3–6): Soluble in oil; stabilizes W/O (water-in-oil) emulsions.
- Intermediate HLB (7–9): Excellent wetting agents.
Calculating Required HLB for Stability
To achieve maximum stability, the HLB of your emulsifier blend must match the “Required HLB” of the oil phase. Since a single surfactant rarely hits this exact number, formulators blend a low HLB Span with a high HLB Polysorbate (Tween).
The Calculation Formula:
% Surfactant A = (Required HLB - HLB B) / (HLB A - HLB B) * 100
By using this calculation, engineers can precisely tune the emulsifier system to the oil phase, preventing creaming or coalescence.
📚 Need the Big Picture?
You are reading a detailed chapter on a specific topic. To understand the complete chemistry, manufacturing process, and full application range of the Span Series, check out our central guide.
2. Physical Properties: Solubility & Viscosity
Beyond HLB, the functional performance of a sorbitan ester is dictated by its physical state and solubility profile.
Solubility Profiles
- Oil Solubility: Most Span esters (especially Span 80 and Span 85) are highly soluble in oils and organic solvents. This makes them ideal for agrochemical concentrates and industrial lubricants.
- Water Solubility: Generally insoluble. They disperse in water rather than dissolving. Span 20 is an exception; due to its shorter lauric acid chain, it is dispersible in water and can form cloudy solutions, making it a versatile co-solubilizer.
Viscosity and Texture Control
The rheological impact is critical for processing:
- Liquid Spans (20, 80, 85): Low viscosity at room temperature. Ideal for sprayable formulations, cutting fluids, and pumpable lotions. Portée 80 is particularly valued for its fluidity despite its long C18 chain (due to unsaturation).
- Solid Spans (40, 60): Waxy solids or beads. Span 60 (mp: 52-57°C) is used to build structure. When melted and crystallized, it forms a network that thickens creams and stabilizes whipped toppings against collapse.
3. Industrial Applications and Formulation Strategies
The versatility of Sorbitan Esters allows them to solve multiple formulation challenges with a single additive.
A. Textile Industry: Lubrication & Static Control
Processing synthetic fibers generates friction and static.
- Lubrication: Portée 80 forms a thin, uniform film on fiber surfaces, reducing fiber-to-metal friction and minimizing breakage during high-speed spinning.
- Antistatic: Spans with higher HLB values attract a microscopic layer of moisture to the fiber surface, dissipating electrical charge. This prevents fibers from clinging to machinery.
B. Agrochemicals: Pesticide Efficacy
In Emulsifiable Concentrates (ECs) and Suspension Concentrates (SCs), uniformity is key.
- Emulsification: Spans (often paired with Tweens) ensure the pesticide concentrate emulsifies spontaneously when diluted in the farmer’s tank.
- Penetration: They act as wetting agents, helping the active ingredient penetrate the waxy cuticle of plant leaves.
C. Paints & Coatings: Pigment Dispersion
- Dispersant: Sorbitan esters adsorb onto pigment particles. The lipophilic tail extends into the solvent phase, creating a steric barrier that prevents re-agglomeration (flocculation). This results in higher color strength and gloss in solvent-based paints.
D. Polymer Processing: Antifogging
- Antifogging: Span 60 is used as an additive in food packaging films. It migrates to the film surface and modifies surface tension, preventing moisture from forming droplets (fog) and ensuring the film remains transparent.
Summary Selection Guide
Choosing the optimal sorbitan ester is a function of the required HLB and the physical nature of your application.
| Industry Challenge | Recommended Grade | Key Mechanism |
| W/O Emulsion (Liquid) | Portée 80 | Low HLB, high oil solubility |
| W/O Emulsion (Cream/Paste) | Span 60 / Span 40 | Structure building via crystallization |
| Pigment Wetting | Span 20 / Span 80 | Surface adsorption |
| Fiber Lubrication | Span 80 / Span 85 | Film formation, friction reduction |
| Aeration (Whipped Goods) | Span 60 | Air bubble stabilization |
Ready to optimize your formulation?
À FoodEmul.com, we provide high-purity Sorbitan Esters tailored to your specific industrial needs. Contact us today for technical data sheets, samples, or formulation advice.
