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The measurement of contact angle of liquids with a range of surfaces can provide a wealth of information. When used with reference liquids it can be used the calculate the surface free energy of the material. It can also be used to assess the wettability of a liquid on a given surface. For example water on water proof materials. Contact angle measurement data is particularly important in relation to surfactants, inks and paints.

LPD Lab Services Ltd uses state of art equipment for the measurement of contact angles of liquids on surfaces supplied by Dataphysics Optical Contact Angle (OCA35).

The equipment uses a high quality imaging system to capture images of a liquid drop as it is placed on a test surface. This allows the drop to measured in real time. The data can then be analysed to monitor the change of contact angle versus time. The volume of the drop can also be calculated understand if the surface is absorbing the liquid. Dynamic contact angles can be measured by monitoring the advancing and receeding contact anagle as the drop volume on the surface is dynamically changed.
 

OCA Instrument

The Data Physics OCA (Optical Contact Angle) measurement device assure the most precise surface/interfacial measurements, through state-of-the-art optics, highly-precise mechanical systems, fast electronic controllers, and high speed/resolution video cameras.

The OCA measurement system provides the following functions:

• Measurement of static and dynamic contact angles on plane, convex, and concave surfaces.
• Measurement of the contact angle hysteresis.
• Calculation of the surface free energy of solids, as well as their contributions (polar/disperse) according to nine different theories.
• Representation of wetting envelopes and work of adhesion/contact angle diagrams.
• Measurement of surface and interfacial tensions, based on the analysis of the drop shape of pendant drops or lamella.
• Determination of absorption properties.
• Analysis of the real and imaginary part of the interfacial dilatational modulus based on the oscillating or relaxing contour of pendant drops.
   

DCAT Instrument

Alternatively LPD can use a Dataphysics Dynamic Contact Angle Tensiometer (DCAT21) for the measurement of contact angles using the Wilhemy plate method. Test surfaces are lowered into reference liquids and the weight changes measured translated into contact angle data. By dynamically raising and lowering the surface in the liquid the dynamic contact angle can also be measured.

In addition by combining the contact angle measurements with other surface analysis techniques available at LPD Lab Services such as XPS, SIMS and AES, a deeper understanding of the surface chemistry can be obtained.
The physical behaviour can also be examined by using scanning electron microscopy (SEM) as surface roughness affect microscopic wetting and localised contact angles.
The combination of contact angle and surface tension measurements, surface texture / roughness and surface chemical analysis is a powerful tool to unambiguously assess manufacturing processes, product performance or reliability.

Typical applications of contact angle measurements include:

• Surface free energy
• Fibre wetting
• Dynamic contact angle data ( Advancing and Receeding Contact Angle)

Industrial applications of surface tension data include:

• Petrochemicals
• Paints and Coatings
• Printing and Inks
• Paper and Coatings
• Polymer Wetting
• Agrochemicals
• Cosmetics and Healthcare
• Microelectronics Wafer Surface Cleanliness

If you would like to discuss your measurement requirements in more detail call us now.

Document Title	View
Determination of Surface Tension and Wettability of Liquid on Solid Surfaces