Surfactants and Cleansing Products

By: Eric Abrutyn, TPC2 Advisors Ltd., Inc.

Posted: June 30, 2009, from the July 2009 issue of Cosmetics & Toiletries.

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Fundamentals to formulating a successful cleanser construction include determining which part of the body is to be cleaned; foam size and structure; ease of foam building; feel during application and after rinse-off; viscosity during dispensing and use; and deposition of active ingredients. In addition it is necessary to development an aesthetically pleasing product that consumers will continue to use. Finally, since in-process foaming is a concern, consideration of the equipment to be used during formulation is of importance; and since surfactants need to dissolve quickly and fully, variables such as equipment, order of addition of ingredients (to include surfactants), mixing rate and temperature must be considered.

Ingredient Selection
Selecting a surfactant system is difficult due to the diversity of options available. To determine the appropriate system, formulators must consider the interaction of ingredients and how surfactant-based cleansing systems will be positioned in the marketplace. Also not to be forgotten is the purchase of ingredients from reliable suppliers. Since no two raw material manufacturers use the same process(es), some manufacturer variations exist that could impact the quality and performance of ingredients. Surfactant specifications are critical to ensure viscosity control and color, odor, pH, salt content and foaming/cleansing characteristics.

While constructing a cleanser, it is helpful for the formulator to divide the formula into its functional segments:

• Water
• Primary surfactant(s): workhorse ingredient(s) required to remove soil from a substrate
• Co-surfactant(s): to add structure or foam density to a formula; these materials, such as alkanolamide MEA and betaines, are conducive to forming a micellar structure that confers higher viscosity
• Rheology modifier(s): consisting of the two types—polymeric and high melting point wax. Polymeric thickeners include acrylate chemistries, cellulose and gums such as guar, xanthan and locust. High molecular weight/melting point waxes such as stearyl alcohol and PEG esters produce crystalline structures that provide suspension for insoluble components.

Performance properties of rheology modifiers include: controlling rheology and yielding stress, modifying the formula’s appearance, flow and texture to alter the pour and at-rest characteristics; stabilizing oils and suspended particles; thickening surfactants—i.e., those that do not thicken with the addition of salt; modifying aesthetics to impart a modified feel during application; and stabilizing viscosity—i.e., preventing viscosity drift during long-term and high-temperature conditions.

• Preservative(s): since cleansing products are generally based on aqueous systems at a relatively neutral pH, preservatives are critical to maintaining a system that is free from micro-organisms.
• pH Adjuster(s): alkaline and/or acidic (e.g., sodium hydroxide and citric acid)
• Miscellaneous functional ingredients: for conditioning, pearlizing, etc.
• Color and fragrance
• Commercial Products

Regarding cleansers, recent advances have been made in milder and softer-feeling surfactants. With the advent of naturalness as a desired attribute, change is continuing. Formulas 1-6 are commercial examples of various cleansing systems on the market. These formulas were taken from sources of public domain and are estimates of the ingredient percentages and procedures used, to provide readers with a starting point for their own formulation work. It is suggested that readers perform a patent search to ensure they are not infringing on any existing and protected technologies.