Sodium dibutyl naphthalene sulfonate (SDNS) is an anionic surfactant with the molecular formula C18H23NaO3S and a molecular weight of approximately 342.43 g/mol. It is characterized by a hydrophobic dibutyl naphthalene tail and a hydrophilic sulfonate head, making it amphiphilic and effective in reducing surface tension.

Below are its key surfactant properties:

• Wetting Ability: SDNS significantly lowers water’s surface tension, enabling better spreading and penetration on surfaces. This makes it ideal for applications like textile processing, leather tanning, and agricultural formulations where uniform coverage is critical.
• Dispersing Power: It prevents particle aggregation in suspensions, enhancing stability in products like concrete (as a superplasticizer), paints, and pigments.
• Emulsifying Properties: SDNS stabilizes oil-in-water and water-in-oil emulsions, useful in cosmetics, creams, lotions, and industrial formulations.
• Hydrotropic Action: It enhances the solubility of other surfactants or hydrophobic compounds in water, beneficial for cleaning products and cosmetic formulations.
• Solubility: Highly soluble in water due to the sodium sulfonate group, with some solubility in organic solvents. The dibutyl derivative is less soluble than mono-butyl or di-isopropyl variants but offers superior wetting and emulsifying properties.
• Stability: Stable in acidic, alkaline, and hard water environments, with good tolerance to calcium and magnesium ions. It maintains efficacy at high temperatures (up to ~100°C) and is resistant to hydrolysis.
• Foaming: Exhibits moderate foaming, with higher foam production compared to lower molecular weight alkyl naphthalene sulfonates.

Applications:

• Textile Industry: Used as a penetrating and wetting agent in refining, bleaching, and dyeing, though it may cause textiles to feel hard and reduce dye vibrancy.
• Construction: Acts as a dispersant in concrete superplasticizers, improving workability and reducing water content by 20-25%.
• Agriculture: Enhances pesticide and herbicide spread and adhesion on plant surfaces.
• Cleaners and Detergents: Boosts wetting and soil removal in household and industrial formulations.
• Leather Tanning: Improves penetration and distribution of tanning agents.
• Emulsion Polymerization: Stabilizes latex and polymer emulsions during manufacturing.

Physical Properties:

• Appearance: White to beige powder or light yellow transparent liquid.
• pH (1% solution): 7.0–9.0.
• Density: 0.5–0.8 g/cm³ (powder); 1.075–1.12 kg/L (17-20% liquid).
• Stability: Flammable in solid form; moderate skin, eye, and respiratory irritation risk.

Synthesis: Produced by sulfonating dibutyl naphthalene with sulfuric acid or oleum, followed by neutralization with sodium hydroxide or sodium carbonate.

Limitations:

• May harden textiles and reduce dye brightness in textile applications.
• Less environmentally friendly than bio-based surfactants; biodegradability data is limited.
• In some applications (e.g., high-performance concrete), it may be outperformed by polycarboxylate ethers.

Safety:

Non-hazardous but requires personal protective equipment to avoid dust inhalation and skin/eye contact. Store in a cool, dry place away from sunlight.