The chemical name of Span S-40 is sorbitan monopalmitate (also known as sorbitan monopalmitate), CAS No. 26266-57-9, molecular formula C22H42O6, molecular weight about 402.6. This product is a nonionic surfactant obtained by the esterification of sorbitol (after dehydration to form sorbitan) with palmitic acid (hexadecanoic acid). It appears as a white to pale yellow waxy solid, melting point 45~47°C, insoluble in water, but soluble in hot oils and various organic solvents.
From the perspective of component composition, Span S-40 is not a single compound but a mixture of sorbitan palmitates. According to measured data from the Guoli Chemical Product Database, the monoester content (one molecule of sorbitan combined with one molecule of palmitic acid) is about 55%, the diester content is about 45%, free alcohol (unreacted polyol) ≤1%, and moisture ≤1.5%. This natural ratio of monoester to diester endows the product with excellent water-in-oil (W/O) emulsifying ability, with an HLB value of 6.7, making it especially suitable as an emulsifier for water-in-oil emulsions.
As a nonionic surfactant, Span S-40 has good chemical stability and wide compatibility. Its acid value ≤8 mg KOH/g, saponification value 140~150 mg KOH/g, hydroxyl value 255~290 mg KOH/g, iodine value ≤10, reflecting high saturation of fatty acid chains and good oxidative stability. The product complies with food additive standards such as FDA 21 CFR 172.842, and has extremely high safety (rat acute oral LD50 > 10 g/kg). It is widely used in food, cosmetics, pharmaceuticals, pesticides and other fields.
| Parameter | Specification |
|---|---|
| Active Ingredient Content | ≥99% |
| Monoester Content | about 55% |
| Diester Content | about 45% |
| Free Alcohol | ≤1% |
| Moisture | ≤1.5% |
| Acid Value | ≤8 mg KOH/g |
| Saponification Value | 140~150 mg KOH/g |
| Hydroxyl Value | 255~290 mg KOH/g |
| Iodine Value | ≤10 |
| HLB Value | 6.7 |
| Heavy Metals (as Pb) | ≤10 mg/kg |
| Arsenic (As) | ≤2 mg/kg |
Based on its main component characteristics (nonionic, HLB 6.7, W/O emulsifying tendency), Span S-40 performs outstandingly in the following scenarios: