Sorbitan esters, often referred to as Spans, are derived from the esterification of sorbitol with fatty acids. This process results in a range of molecules with varying degrees of esterification and HLB (Hydrophilic-Lipophilic Balance) values.

Low HLB Sorbitan Esters:
- Sorbitan monostearate (HLB 4.7): Ideal for stabilizing water-in-oil (W/O) emulsions due to its lipophilic nature.
High HLB Sorbitan Esters:
- Sorbitan monolaurate (HLB 8.6): Suitable for oil-in-water (O/W) emulsions.

Polysorbates (Tweens)

Polysorbates, or Tweens, are non-ionic surfactants derived from sorbitan esters through ethoxylation. This process increases their hydrophilicity, making them suitable for various applications.

Polysorbate 20: With an HLB of 16.7, it is highly hydrophilic and effective in stabilizing oil-in-water emulsions.
Polysorbate 60: An intermediate HLB of 14.9 makes it versatile for both O/W and W/O emulsions.
Polysorbate 65: With an HLB of 10.5, it is more lipophilic and suitable for W/O emulsions.
Polysorbate 80: With an HLB of 15, it is widely used as an emulsifier, solubilizer, and stabilizer in various industries.

Key Properties and Applications:

Emulsification: Both sorbitan esters and polysorbates are excellent emulsifiers, enabling the formation of stable dispersions of oil and water.
Solubilization: They can solubilize hydrophobic substances in aqueous solutions.
Surface Activity: They reduce surface tension, improving wetting and spreading properties.
Stabilization: They stabilize emulsions and suspensions, preventing phase separation.
Food Industry: Emulsifiers, stabilizers, and wetting agents.
Cosmetic Industry: Emulsifiers, solubilizers, and surfactants.
Pharmaceutical Industry: Excipients, solubilizers, and emulsifiers.
Industrial Applications: Detergents, cleaners, and textile processing.