Speciality Chemicals Magazine NOV / DEC 2025 | Page 32

Alkyl ether sulfates, for example sodium laureth-2 sulfate( SLES) are commonly used in cosmetics, household, such as dish detergents and industrial cleaning applications. Ethoxylation of the alkyl group improves water solubility and increases mildness on the skin, though they can still be drying and interfere with skin barrier function. Higher amounts of ethoxylation can reduce foamability compared to the non-ethoxylated AS counterparts.

Sodium dodecylbenzene sulfonate( SBDS) is used in household cleaning products where it provides a strong, lasting foam. Particularly stable in alkaline conditions, sodium C14-16 olefin sulfonate can offer good hard water stability and biodegradability. High foaming and cleansing ability lend it to household and personal care applications, where it is often used in shampoo formulations.

Sulfosuccinates like sodium laureth sulfosuccinate offer exceptional mildness but with a lower cleaning power than SLES. They are typically used in personal care products aimed at sensitive skin or baby products. Better foaming characteristics are observed at neutral to alkaline pH.

The charge on amphoterics, for example cocamidopropyl betaine( CAPB) or lauryl betaine, is pHdependant. In acidic solutions, the basic amine group protonates, creating a net positive charge and cationic behaviour. In neutral pH, they become zwitterionic, while at alkaline pH they behave as an anionic.

This flexibility enables them to be used in combination with anionic, cationic and nonionic surfactants where they can boost foam and enhance the mildness of a formulation. A commonly used amphoteric surfactant, cocamidopropyl betaine( CAPB) is commonly used in personal care applications where it can boost foam, synergistically alter rheology with alkyl ether sulfates and reduce irritation.

Nonionics like lauramine oxide have lower foaming efficacy than anionics but as a secondary surfactant it provides excellent foam boosting properties utilised in personal care and household cleaning.

Alkyl glucosides like lauryl glucoside exhibit the lowest skin irritation profile. These are widely used in‘ mild’ personal care applications and laundry cleaning products, especially for sensitive skin. They offer mild cleansing and good biodegradability but lower flash foam generation than the alkyl sulfates.

Typically used in combination with other surfactants in personal care products aimed at delicate skin. polyoxyalkylene glycol fatty alcohol ethers( AEOs) are low-foaming surfactants with great cleaning benefits and the ability to‘ wet out’ contaminants. Typically used in household surface cleaning sprays where they offer high pH tolerance. In our testing an AEO was included to demonstrate a surfactant with a lower foam and foam stability characteristic.

Gentle glycolic foam cleanser

Material % Active Surfactant % INCI DI water To 100 % Aqua CorFactant CAPB LS 35 8.57 3 Cocamidopropyl Betaine CorFactant LAO 5 1.5 Lauramine Oxide Pationic ISL 0.5 0.5 Isostearoyl Lactylate Glycolic acid 70 % 4.29 Glycolic Acid Glycerin 3 Glycerin

NaOH 10 % solution qs to pH 3.5 – 4

Spray power foam / kitchen degreaser

Material % Function DI water To 100 %

Figure 3 – Formulations with surfactant blends

Sodium Hydroxide

CorFactant CAPB 30 % 2 Amphoteric foam booster

Butyoxyethanol 3 Solvent Sodium citrate 0.8 Chelator

Quantifying foam performance

To compare surfactant volume and stability two test were conducted, a laboratory sparge and foamer pack dispenser test. 4 For both tests, 1 % active surfactant solutions were prepared in deionised water. The solutions pH was adjusted to pH 3.5 for acidic testing and pH 8.5 for alkaline. This is a much lower inclusion of surfactant than typical of a cleaning product, but was chosen to highlight variations in the surfactants’ foam creation and stabilisation ability.

In the sparge test, ten seconds of aeration from a bubble stone was applied to a 100 ml test solution. Foam volume and stability were quantified over time, revealing distinct differences in foam strength, persistence, and collapse rates( Figures 1 & 2). The same 1 % solutions were then filled into cosmetic type foamer packs and five pumps were dispensed onto a tile for foam observation.

Citric acid / NaOH qs to pH 8.0 – 9.0 pH adjustment

32 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981