Span 80, also known as sorbitan monooleate, is a nonionic surfactant and emulsifier. It belongs to the family of sorbitan esters. This ingredient is produced by esterifying sorbitan with oleic acid, a fatty acid in many vegetable oils. Span 80 emulsifier presents as a light yellow, viscous, oily liquid. Its solubility characteristics include insolubility in water and solubility in organic solvents. Span 80 is an emulsifier, stabilizer, and dispersant used in the food, pharmaceutical, and cosmetics industries.

Tween 80, also known as Polysorbate 80, is derived from the reaction of sorbitol with ethylene oxide, resulting in a polyethoxylated sorbitan ester. It is a water-soluble, hydrophilic surfactant. Polysorbate 80 for sale is used as a solubilizer, emulsifier, and stabilizer in food, pharmaceuticals, and cosmetics.

While both Span 80 and Tween 80 have emulsifying properties, their chemical structures, solubility characteristics, and applications differ. Span 80 is primarily used in oil-based formulations, whereas Tween 80 is water-soluble and commonly used in water-based or aqueous formulations.

Span 80 and Tween 80 are biodegradable surfactants that can be added to blended fuels, such as hydrated bioethanol–gasoline and methanol–gasoline. They increase the fuels' water tolerance and reduce their corrosive properties without altering their fuel characteristics.

In many studies, a mixture of Tween 80, which is a hydrophilic surfactant, and Span 80, a hydrophobic surfactant, was employed. First, this reduces corrosion because surfactants adhere strongly to metal surfaces, forming a barrier to water ingress[1]. The Span 80 and Tween 80 surfactants have hetero oxygen atoms and good anti-corrosive activity in a hydrocarbon medium. Second, the mixture acts as an emulsifier and improves the water tolerance of the methanol/ethanol–gasoline blend. Span 80 has an HLB value of 4.3, which falls within the usual HLB 4–6 range for water-in-oil (W/O) emulsifiers. Tween 80 has an HLB value of 15, within the range of HLB 8–18 for oil-in-water (O/W) emulsifiers.

[1] Mohamed G.A. Kassem. “Use of Span 80 and Tween 80 for blending gasoline and alcohol in spark ignition engines.” Energy Reports 5 (2019): Pages 221-230.