Sodium Lauryl Ether Sulfate

Uses

Sodium lauryl ether sulfate (SLES) is the world's most widely used anionic surfactant in personal care formulations, valued for its combination of excellent cleansing, foaming, and skin compatibility.

In shampoos, SLES is the primary surfactant at concentrations of 8–15% actives, providing the backbone cleansing and foaming performance. It is typically combined with cocamidopropyl betaine (CAPB) as a mild secondary surfactant and foam booster, sodium chloride as a viscosity builder, and conditioning agents (silicones, cationic polymers) to create balanced shampoo formulations for different hair types.

Body washes, shower gels, and liquid hand soaps use SLES at 8–20% actives, with mild secondary surfactants, moisturizers (glycerine, glycols), and emollients to deliver cleansing performance with good skin feel and mildness. Baby care products (baby shampoos, baby washes) use ultra-mild SLES variants (higher EO degree, e.g., SLES-3) for enhanced eye and skin mildness.

Household and industrial cleaning applications include dishwashing liquids (SLES at 15–30% actives with non-ionic co-surfactants), multi-purpose cleaners, laundry detergents (in combination with LAS and non-ionics), and hard surface disinfectants. In industrial applications, SLES is used in textile wet processing, leather degreasing, car wash concentrates, and oilfield production chemicals.

In construction and building materials, SLES is used as a foaming agent in foam concrete production, and as a wetting agent in cement and concrete admixtures. In fire fighting, SLES-based formulations are components of aqueous film-forming foam (AFFF) concentrates.

Methods of Manufacturing

SLES is produced in a two-step process: ethoxylation of fatty alcohol followed by sulfation and neutralization.

Step 1 — Ethoxylation: Lauryl alcohol (or C12–C14 lauryl/myristyl alcohol blend) reacts with ethylene oxide (1–3 moles per mole of alcohol) in the presence of KOH catalyst at 140–180 °C and 2–5 bar pressure in a closed reactor (loop or tubular reactor). The degree of ethoxylation (average EO units, n) determines the mildness and performance: SLES-2 (n=2) is standard, SLES-3 (n=3) is milder for baby care.

Step 2 — Sulfation and Neutralization: The ethoxylated fatty alcohol (laureth-2 or -3) reacts with gaseous SO₃ in a falling film reactor at 40–60 °C. The resulting lauryl ether sulfuric acid is immediately neutralized with aqueous NaOH solution to pH 7–8, yielding the sodium salt (SLES) as an aqueous solution of 28–70% active content.

Quality control parameters include active matter content (MBAS titration), unsulfated material, pH, color (APHA), viscosity, dioxane content (formed as trace byproduct in ethoxylation, regulated in personal care products), sodium sulfate, and odor.

Hazard Summary

Mild to moderate skin and eye irritant. Lower irritation potential than SLS. May cause sensitization in some individuals.

Fire Hazard

Non-flammable aqueous solution under normal conditions.

Skin, Eye & Respiratory Irritations

Milder skin and eye irritant than SLS; still may cause irritation on prolonged contact or at high concentrations.

Physical Dangers

Non-flammable aqueous solution.

Skin First Aid

Wash with soap and water thoroughly.

Eye First Aid

Flush immediately with water for 15 minutes. Seek medical attention.

Ingestion First Aid

Rinse mouth with water. Seek medical attention.

Fire Fighting Procedures

Use water spray, CO₂, or foam.

Nonfire Spill Response

Small spill: Absorb with inert absorbent material or dilute with large amounts of water. Collect in labeled containers. Prevent foamy material from entering drains and waterways.

Large spill: Contain with bunds to prevent spreading. Do not use water hose — foaming will worsen the spill. Pump concentrated material into recovery containers. Dilute residual with large volumes of water before draining (high foaming, high BOD). Notify environmental authorities for significant spills.

Safe Storage

Store in original, tightly closed containers in a cool, dry, well-ventilated area. Do not store in galvanized or unlined carbon steel containers — use HDPE or stainless steel. Protect from frost (freezing causes product separation/instability). Keep away from strong acids (cause hydrolysis and loss of active matter). Do not store near strong oxidizing agents or foods.

Storage Conditions

Recommended storage temperature: 10–30 °C. Do not allow to freeze (protect from frost). Avoid storage above 40 °C for extended periods (thermal degradation). Shelf life: 12 months in original sealed containers at recommended temperature. Suitable containers: HDPE tanks, stainless steel 304/316. Protect from direct sunlight. Recirculate or rehomogenize before use if stored for a long time.