Surfactants are organic molecules that modify the surface forces, i.e., the attraction between molecules of a liquid on its surface. They are used in detergents as they help to dissolve or emulsify water-insoluble substances. Surfactants have emulsifying, wetting, detergent and foaming properties.
When surfactants dispersed in water are subjected to shaking, they usually create foam. A detergent is often expected to produce abundant and persistent foam, and consumers associate it with good product quality. Only a small proportion of the foam is formed by surfactants, but they are essential for its formation and stabilisation.
However, in some applications, foaming is not desirable, whether because it reduces the effectiveness of the detergent or because it hinders the use of the product. In cleaning processes where there is strong mechanical energy, such as in automatic dishwashers, CIP (Clean-in-place) additives or industrial detergents (I&I) for surface washing, foaming impedes the proper functioning of the equipment. In other applications, such as industrial laundry, the detergents that form unstable and rapidly collapsing foams are appreciated. In these cases, foam fills tanks, hinders the normal operation of sprayers or prevents rinsing of detergents, and low-foaming surfactants are then the solution.
What are low-foaming surfactants?
Low-foaming surfactants are characterised by a reduced foam volume, and this is especially useful in cleaning processes with high mechanical energy.
Some examples of applications where low-foaming surfactants are used are:
- Automatic dishwashing detergents and household rinse aids.
- CIP detergents in the food and dairy industry.
- In metal processing or metal cleaning.
- In the paper industry.
- In textile processing.
- In pigment dispersions.
Foaming can compromise effectiveness
In all these uses, foaming compromises detergent performance, and high-performance products with excellent detergency and wetting properties are required, but also doing so without foaming or even as defoamers.
Ethoxylated and propoxylated surfactants
Ethoxylated and propoxylated surfactants are the most interesting low-foaming ingredients. These non-ionic alkoxylates, containing ethylene oxide (EO) and propylene oxide (PO), provide excellent spray cleaning performance in addition to easy rinsing. They are very useful in mechanical cleaning processes with high shaking.
These surfactants can be combined with other low foaming components, such as hydrotropes, to formulate safe and cost-effective cleaners.
The properties of each product depend on the length and type of the fatty alcohol forming the surfactant, but also on the degree of ethoxylation and propoxylation and its configuration in the molecule. The many possibilities for variation in these aspects provide an extensive range of products, allowing the best solution to be found for each application.
Other low-foaming surfactants
There are medium to low foaming amine oxides,
used for their detergent performance in cleaners and degreasers. When combined with low-foaming hydrotopes, amine oxides are key in hard surface cleaners and metal cleaning.
Some fatty alcohol-derived ethoxylates can also offer moderate to low foam profiles and are used in a wide range of hard surface cleaning or laundry applications. These surfactants provide excellent detergent and wetting properties, along with the benefits of environmental, health and safety profiles.
Short-chain alkyl polyglycosides are also used in applications where moderate to low foaming is required.