Mobile Surface Tension Measurement

Surfactants as wetting or cleaning agents change the surface tension. Measurement of the dynamic surface tension with the hand-held device BP50 reveals directly on site whether sufficient surfactant is dissolved.

Concentrations above the critical micelle concentration (CMC), as is characteristic for cleaning baths, cannot be distinguished with static measurements of the surface tension. However, the dynamic bubble pressure method of the BP50 reacts sensitively to changes in concentration even above the CMC.

For high-speed processes such as printing, spraying or coating, it is the dynamic surface tension in the short-term that is decisive. The dynamic bubble pressure technique of the instrument detects the surface tension which occurs just after surface formation at surface ages between 15 and 16,000 ms.

The measuring system, consisting of capillary, compressor, pressure sensor and a temperature sensor, is contained in a mobile hand-held instrument – for on-site measurements. Disposable plastic capillaries do away with the hydrophobizing process necessary for glass capillaries. The instrument works almost independently of the capillary immersion depth – a clear advantage for rapid tests. Water or other solvents can be used for calibration at different temperatures.

The measurement is defined and the instrument controlled by the BP50 add-in for LabDesk, the well-proven universal platform for Krüss tensiometers. Various measuring programmes record the time-dependent surface tension or the measured value curve for a constant surface age – or they evaluate a measured value as being valid or invalid in the rapid quality test. The database is comfortable and flexible; well-laid-out reports are quickly produced.