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An Easy Guide to Understanding Surfactants and how they Work.

So What is a Surfactant? Surfactants are the primary component of cleaning detergents, and they do their best work when they're in a solution.

Surfactants act to reduce tension at the surface or interface between two different phases or substances. By stirring up activity on the surface, they help to trap dirt and remove it. They are able to act in this way because they contain both a hydrophilic (water loving) group, such as an acid anion, and a hydrophobic (water hating) group, such as an alkyl chain.

So How do Surfactants work? When there is a sufficient concentration of surfactant molecules in a solution, these molecules combine together to form structures called micelles. As micelles form, the surfactant heads position themselves so that they are exposed to water, while the tails are positioned in the center of the structure where they are protected from water. The micelles work as a unit to remove soils and debris. The hydrophobic tails are attracted to soils and surround them, while the hydrophilic heads pull the now surrounded soils off of the surface and into the solution. The micelles then reform with the tails suspending the soil in the center of the structure.

The hydrophilic head of each surfactant is electrically charged. The charge can be negative, positive, or neutral, and based on the charge a surfactant can be anionic, nonionic, cationic, or amphoteric. These four categories are summarized as follows:

  • Anionic: negative charge at the hydrophilic head

  • Nonionic: no charge at the hydrophilic head

  • Cationic: positive charge at the hydrophilic head

  • Amphoteric: both positive and negative charges at the hydrophilic head

Anionic surfactants are frequently used in soaps and detergents because they are able to attack a broad range of soils. They create a lot of foam when mixed, and are excellent at lifting and suspending particulate soils, but are not as good at emulsifying oily soils. Sulfates, sulfonates, and gluconates are all examples of anionic surfactants. Anionic substances and solutions do not ionize in aqueous solutions; as such, they are effectively used to create corrosion-inhibiting surfactants.

Nonionic surfactants are very good at emulsifying oils and are better than anionic surfactants at removing organic soils. Nonionic and anionic surfactants are sometimes used together in order to create dual-action multipurpose cleaners. Certain nonionic surfactants are non-foaming or low-foaming, making them a good choice for low-foaming detergents. Ethoxylates, alkoxylates, and co-amides are examples of nonionic surfactants. Some examples would be Tide and Wisk.

Cationic surfactants are useful in anti-static products such as fabric softeners, and can also serve as antimicrobial agents in disinfectants. They are not compatible with anionic surfactants since mixing positively charged with negatively charged surfactants will cause them to fall out of solution and no longer be effective. Cationic and nonionic surfactants are compatible. Alkyl ammonium chlorides are anionic surfactants.

Amphoteric surfactants’ dual charges cancel each other out creating a net zero charge, referred to as zwitterionic. In acidic solutions, amphoteric surfactants become positively charged and behave similarly to cationic surfactants, while in alkaline solutions they become negatively charged and behave similarly to anionic surfactants. Amphoteric surfactants are often used in shampoos and cosmetics. Betaines and amino oxides are examples of amphoteric surfactants.

How does this relate to Automotive cleaning? Using Formulated Cleaners - Formulated cleaners usually contain four basic elements: surfactants, hydrotropes, builders and carriers. Hydrotropes are chemicals that keep the otherwise incompatible surfactants and builders stable in a solution. The carrier is either water or a solvent. These elements work together to create mechanical actions to remove soils. The end result is a product that can attack dirt on surface of the vehicle with a variety of cleaning mechanisms including emulsifying, lifting, dispersing, sequestering, suspending and decomposing soils of various types. Using the correct surfactants is what is key in AG Products Car Care Cleaners and Detailers.

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