Dec. 23, 2024
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.
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The classification of surfactants is based on the charge they possess when dissociated, and they are differentiated into anionic, cationic, amphoteric and non-ionic.
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.
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:
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 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.
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.
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Foam is an important property when choosing a surfactant for your cleaning formulation or processing application.
For example, in manual hard surface cleaning applications, such as vehicle care products or liquid hand dish wash, generating high foam levels is usually a desirable feature.
This is because the presence of high and stable foam indicates that the surfactant is activated and performing its cleaning functions.
Conversely, for many industrial cleaning and processing applications, foaming can interfere with certain mechanical cleaning actions and inhibit overall performance.
In these cases, formulators need to use low foam surfactants to deliver the desired cleaning performance while also controlling foam levels.
The purpose of this article is to introduce low foaming surfactants and provide a starting point for surfactant selection in low foam cleaning applications.
Foam is caused by agitation at the air-surface interface.
As such, cleaning actions with high agitation, high shear mixing or mechanical spraying often require appropriate foam control surfactant chemistry.
Examples of such applications include:
Selecting a surfactant or combination of surfactants for foam control begins with analyzing foam measurements.
Foam measurements are provided by surfactant producers in their technical product literature. For reliable foam measurements, the data sets should be based on well-recognized foam testing standards.
Two of the most common and reliable foam tests are the Ross Miles Foam Test and the High Shear Foam Test.
The Ross-Miles Foam Test evaluates surfactant initial foam generation (flash foam) and foam stability at low agitation in water.
This test may include readings of an initial foam level, and then foam level after 2 minutes. It can also be conducted at different surfactant concentrations (i.e. 0.1% and 1%) and pH levels.
Most formulators seeking low foam control place the emphasis on initial foam measurements.
Using the Ross Miles test, low foam surfactants are defined as producing less than 5 cm initial foam height, or a break to less than 5 cm in 2 minutes.
The Ross Miles standard can be found in ASTM D.
General Foam Classifications Using the Ross-Miles Foam Test
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The Ross Miles test is often favored by formulators due to its sensitivity to surfactant structure, active surfactant concentration and changes in composition.
For high agitation mechanical processes, such as those processes where low foam surfactants are usually required, the high shear foam test can provide a very useful system of foam measurement.
The High Shear method measures the ability of a surfactant to produce foam in simulated agitation environments (i.e. the &#;blender&#; test).
General classifications of foaming using this method include:
The High Shear Test Method can be found in ASTM D-88.
This test compares foam measurements with and without the presence of soils. The High Shear test also compares initial foam height to foam height after 5 minutes.
Based on either of the above test methods, there are several surfactants available on the market that qualify as low foaming ingredients.
However, regardless of the chosen foam test method, a low foam surfactant must also possess other important physical and performance properties.
Depending on the application and cleaning environment, additional properties that are critical to surfactant selection may include:
It is important for formulators to balance these properties with the degree of foam control required in their application.
To strike this balance, it is often necessary to combine different surfactants, thereby targeting both foam and performance needs, or select a low to moderately foaming surfactant with broad functionality.
Low foaming surfactants include several nonionic and amphoteric compounds with a broad range of performance properties and application possibilities.
It is important to note that these surfactants are not zero foamers.
Instead, in addition to other properties, these surfactants provide a method to control the amount of foam generated in certain applications.
Low foam surfactants are also not the same as defoamers or antifoams, which are additives designed solely for the purpose of minimizing or eliminating foam. Surfactants deliver many other essential features to a formulation, including cleaning, wetting, emulsification, dispersing and more.
The following general surfactant categories are examples; but this list only scratches the surface of low foam surfactant technology.
Specific product recommendations within each category will depend on factors that are unique your application.
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Amphoteric surfactants with very low foam profiles are used as hydrotopes in many cleaning formulations. These ingredients provide coupling, stability, cleaning and wetting properties
New multi-functional amphoteric surfactants (i.e. Amphoteric 12), with very low foam profiles, deliver cleaning performance along with excellent environmental and safety profiles and compatibility with other nonionic, cationic, and anionic surfactants.
Low foaming alkoxylates, with ethylene oxide (EO) and propylene oxide (PO) content, can provide excellent rinsing and spray cleaning performance for several high agitation and mechanical cleaning applications.
Examples include: rinse aids for automated detergent applications, dairy and food cleaners, pulp and paper processing applications, textile chemistries, and more.
Moreover, alkoxylates that are based on linear alcohols exhibit very low foam profiles and can be combined with other low foaming components, such as biodegradable hydrotropes, to formulate safe and economical cleaners.
EO/PO block copolymers are known for excellent wetting and dispersing properties.
Low foaming recommendations within this category can serve as highly effective emulsifiers for several industrial and institutional cleaning applications.
Amine oxides with very low foam measurements are also known for detergent performance in cleaners and degreasers.
When combined with low foaming amphoteric hydrotropes, amine oxides can be the surfactant backbone for many formulations in low foam hard surface cleaners and metal cleaning applications.
Certain linear alcohol ethoxylates offer moderate to low foam profiles and can be used in a wide range of hard surface cleaning applications.
These surfactants provide excellent detergency, wetting properties, along with the benefits of preferable environmental, health and safety profiles.
Low HLB alcohol ethoxylates, in particular, are low-to-moderate foamers and can be used in combination with higher HLB alcohol ethoxylates to control foam and enhance oil solubility in many industrial cleaning formulations
Certain fatty amine ethoxylates are low foaming and can be used to deliver emulsification, wetting and dispersing properties in agricultural applications and thickened cleaning or wax based formulations.
If you need to control the amount of foam in your cleaning application, we hope the suggestions in this article can provide a foundation for choosing a surfactant to test in your formulation.
For foam data and compatibility information on specific surfactant compounds, we recommend consulting with the surfactant producer&#;s technical service department.
And if there are any questions we can help with, please feel free to send us a note.
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