• Cleaning sprays

    Cleaning sprays

Application of surfactants

Interfacial chemistry measuring methods for the research and development of surfactants and their technical use 

Emulsifiers, wetting agents, foaming agents, collecting agents - there are a vast number of names for surfactants depending on the areas in which they are used. Surfactants reduce the surface tension or interfacial tension with respect to an adjacent phase and therefore lie at the heart of interfacial chemistry.

With decades of experience in tensiometry, contact angle measurement and foam analysis, we make an important contribution to surfactant research and development. Our measuring methods reflect process conditions such as temperature, pressure and speed or the type of wetting process. Our products enable the use of surfactants to be optimised for the particular application. 

Optimising the wetting of solid surfaces

With technical procedures, the quality of the process or of the end product frequently depends on the wetting of the solid material by an aqueous solution. However, the high surface tension of water often leads to wetting problems. The surface tension can be reduced and better wetting achieved by adding surfactants.

Our tensiometers measure the surface tension precisely and, depending on the requirement, with a high degree of automation. The contact angle, which can be determined by our stationary or mobile drop shape analysis instruments, provides information on the wetting of the solid.

In the case of fast technical processes, such as printing or bonding, the required reduction in surface tension must often take place in fractions of a second. We have designed our bubble pressure tensiometers for measuring dynamic surface tension at surface ages of a few milliseconds.

Connection between water and hydrophobic phases

The washing effect of surfactants is based, on the one hand, on the better wetting of the surface to be cleaned. On the other, surfactants mobilise hydrophobic substances by incorporating them in molecule clusters (micelles). Our fully automatic tensiometers measure the critical micelle concentration CMC, above which these micelles occur. The CMC is an important characteristic for the efficiency of surfactants and frequently determines the necessary dosage.

Emulsions, such as milk or creams, are mixtures which are stable in the medium term of two liquids which are not soluble in one another. They are produced and stabilised with the help of natural or synthetic surfactants as emulsifiers. The droplet size achieved when mixing and the tendency to segregate depend on the interfacial tension.

We have developed a range of tensiometer types for measuring the interfacial tension for different application areas. As well as static measurements with force sensor tensiometers, our drop volume tensiometers also characterise the behaviour of dynamic interface processes. Measurement using spinning drop technology is used for extremely low interfacial tensions, which occur, for example, in enhanced oil recovery (EOR).

Improvement of dispersibility of powders and pigments

In solid-liquid dispersions, interface processes between powder and liquid determine the degree of distribution. Here, surfactants help to improve the mixability and stability.

Our tensiometers measure the surface tension of the liquid which is definitive for the powder wetting. In addition, measurement of the powder contact angle characterises the solid constituents of the mixture. Both analyses lead to an overall picture of the interface behaviour and help with the separate optimisation of the constituents.

Improvement of sprayability

The dispersion of a volume of liquid into many small droplets goes hand-in-hand with an increase in the total surface area. This is easier to achieve the smaller the surface tension. Sprays therefore frequently contain surfactants in order to obtain a fine spray mist.

Spraying is a highly dynamic process in which the surfactants must produce their effect in a very short time. Dynamic surface tension measurements with our bubble pressure tensiometers contribute to the development and optimisation of sprays.

Foam formation and foam prevention

For deliberately produced foams, our foam analysis instruments provide extensive options for investigating the foamability and foam stability, the moisture content, and the bubble size distribution.

In many applications, foams are an undesirable side-effect of adding surfactants. For this reason, foam-inhibiting or foam-reducing agents are often used as well as low-foaming surfactants (low-foamers). Our methods for detecting the foam height measure the tendency to foam and the foam stability, even with foams which have short-term stability.

KRÜSS Application Reports

AR288: From an immiscible water-oil system to the ultralow interfacial tension of a microemulsion

When trying to synthesize microemulsions for applications such as enhanced oil recovery, pharmaceutics, or cosmetics, the interfacial tension can range from 50 mN/m to values as low as 10-5 mN/m. The application report shows how this broad measuring range can be covered using just one instrument.

AR285: Interfacial rheology of emulsifiers in food

The interfacial rheological behavior, i.e. the impact of the deformation of a phase boundary on the surface or interfacial tension, has a strong influence on the stability of emulsions of foams. The Application Report shows how the relevant parameters elastic modulus E’ and viscous modulus E’’ can easily be measured for surfactant solutions typically used in the food industry.

AR268: Kinetic investigations into the effectiveness of surfactants

Five surfactants are investigated with regard to their effectiveness and efficiency in reducing surface tension by means of static and dynamic measurements. The choice of the most suitable surfactant depends on the process speed.

AR267: Foam behavior and foam stability of aqueous surfactant solutions

The foaming and stability behavior of three surfactant low-foaming solutions are characterized. Comparative interfacial rheology measurements provide a good correlation between interfacial rheology parameters and the data from the foam measurements.

AR227: Phase boundaries under pressure

A high pressure cell is used to investigate the dependency of interfacial tension between oil and water and of their densities on pressure applied up to 300 bars (ca. 4000 Psi).

AR214: Analysis of Surfactants for Textile Refining using Static and Dynamic Surface Tension Apparatuses

Biocompatible alkyl polyglucosides are investigated with regard to their suitability for use in the industrial refinement of textiles. Good values of static and dynamic surface tension indicate that they are superior to conventional surfactants.

AR209: Evaluating the Efficacy of Lignosulphonates as Dispersing Agents

Loam suspensions are stabilized with solutions of different lignosulphonates. The quality of the samples as dispersing agents is investigated based on sedimentation measurements.