Span S-40 (CAS No.: 26266-57-9), chemically known as sorbitan monopalmitate, with molecular formula C22H42O6 and molecular weight of approximately 402.6. The product appears as a white to pale yellow waxy solid with a melting point range of 45~47°C, low hygroscopicity, and good chemical stability. As a nonionic emulsifier, its HLB value is 6.7, making it a typical water-in-oil (W/O) emulsifier.
This product is insoluble in water (no cloud point), but soluble in hot oils and most organic solvents. The effective content is ≥99%, moisture ≤1.5%, free alcohol ≤1%, monoester content approximately 55%, and diester content approximately 45%. It is stable under normal storage conditions but should avoid contact with strong acids and alkalis. The flash point is greater than 200°C, and it is not classified as a flammable hazardous material.
| Basic Information | |
|---|---|
| Chemical Name | Sorbitan monopalmitate |
| CAS No. | 26266-57-9 |
| Molecular Formula | C22H42O6 |
| Molecular Weight | ~402.6 |
| Ionic Type | Nonionic |
| Physical Properties | |
| Appearance | White to pale yellow waxy solid |
| Melting Point | 45~47°C |
| Density | ~1.0 g/cm³ |
| Flash Point | >200°C |
| Hygroscopicity | Low |
| Solubility | Insoluble in water, soluble in hot oils and organic solvents |
| Chemical Indicators | |
| HLB Value | 6.7 |
| Effective Content | ≥99% |
| 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 g I2/100g |
| pH Value (1% Dispersion) | 5.0~7.0 |
| pH Value (5% Dispersion) | 5.0~7.0 |
| Surface Tension (0.1%, 25°C) | ~30 mN/m |
| Critical Micelle Concentration (CMC) | ~2.5×10⁻⁵ mol/L |
| Composition Indicators | |
| Monoester Content | Approximately 55% |
| Diester Content | Approximately 45% |
| Free Alcohol | ≤1% |
| Safety and Limits | |
| Heavy Metals (as Pb) | ≤10 mg/kg |
| Arsenic (As) | ≤2 mg/kg |
| Chemical Stability | Stable at room temperature, avoid strong acids and alkalis |
Span S-40 has an HLB value of 6.7, making it a classic low-HLB emulsifier. It is recommended to be used in combination with high-HLB Tween series (e.g., Tween-60, Tween-80) to achieve a wider range of emulsification effects. As a W/O emulsifier, the recommended dosage is generally 1%~5% of the oil phase weight. In cosmetic creams, it is often paired with Tween series in different ratios to adjust the HLB value from 4 to 14, meeting the needs of various O/W or W/O emulsion systems. In the food industry, when used in baking fats and whipped creams, refer to the usage limits specified in GB 2760.