Surfactants:Research and Development

Research and Development of Surfactants

Best instrument for this application:

Laboratory use of the SITA science line t60 in Research and Development

Problem:

Surfactants are used to improve the quality of products in various industrial branches. Hence, it is necessary to investigate and analyze the properties and effects of surfactants. Being surface active is one of the surfactant's most important qualities. Surfactants attach to newly built surfaces. In this way they affect surface tension. The resulting change of surface tension depends on the temperature of the liquid and the concentration of the surfactants. For many applications it is interesting to know how fast the surfactants attach to newly built surfaces and how much the surface tension decreases after a short time. All these effects are the objectives of the investigations into the dynamic behavior of surfactants.

1. Investigating the Effects of Temperature:

The surface tension of liquids depends on their temperature: The surface tension decreases with increasing temperature. As well, the effect of the surfactant on the surface tension is dependent upon temperature. The effect of temperature on the so called "surfactant kinetics" is shown in the following figure.

diagram 1

Surfactants Depending on Temperature

2. Investigating the Effects of the Surfactant's Concentration

The concentration of a surfactant influences its dynamic behavior. For example: one task could be to find out how much surfactant is to be added in order to achieve a defined surface tension at a certain bubble lifetime (age of the surface).

diagram 2

Effects of the Surfactant's Concentration on Dynamic Behavior

3. Investigating the Dynamic Behavior of Various Surfactants

The diagram shows the surface tension of different surfactants against the bubble lifetime. That means how long a surfactant needs to attach to a new generating surface (bubble) and how strong it is lowering the surface tension. The reference graph from water is used as comparison, because water has a constant surface tension by constant temperature at all bubble lifetimes.
A surfactant which has a fast effectivity can lower the surface tension already at short bubble lifetimes very strong. This behaviour could be seen at Surfactant B and D. This is the reason to use them preferred in dynamic processes. With increasing bubble lifetime the surface tension of the surfactants lowers different strong until they reach a nearly constant value. (Surfactant B, D) This value is called the saturation state. The bubble surface is completely coatet with surfactant an a further lowering of the surface tension is not possible.
On the other hand the surfactants A and C are lowering the surface tension primal at highter bubble lifetimes, that means these surfactants are especialy suited for static processes.

diagram 3

Comparison of Different Surfactants in Reference to their Dynamic Behavior

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