Contact angle is a quantitative measure of the wetting of a solid by a liquid. The contact angle is defined geometrically as the angle formed by the liquid at the three-phase boundary where the liquid, gas and solid intersect. There are three different forces acting on this three-phase contact point between solid, liquid and gas or in some cases solid, liquid and liquid. Contact angles can be divided into static, dynamic and roughness corrected contact angle.
Contact angle measurement is used in a wide variety of industries and research areas such as chemicals, pharmaceuticals, electronics, food, energy, paper and packaging.
Static contact angles are measured while the droplet is at the surface and the three-phase boundary is not moving. Static contact angles are by far the most measured wettability values. Most suitable for relatively smooth and homogeneous surfaces. Static contact angles are also used to describe the surface free energy of the substrate, i.e. the surface tension of the solid.
The dynamic contact angle can be measured as the three-phase boundary moves, and these are called advancing and receding angles. The advancing contact angle is measured as the droplet front advances and the droplet front recedes. On an ideal surface, these two values are close to each other. However, often the measured contact angle depends on the direction in which the contact line is moving. The difference between advancing and receding contact angles is mostly due to chemical and topographic heterogeneity of the surface, solution impurities absorbed at the surface, or swelling, rearrangement or alteration of the surface by the solvent.
Contact angles are affected by roughness. Surfaces with the same chemical composition but different roughness have different contact angles. Roughness corrected contact angles are contact angle values at which the effect of roughness is eliminated. Roughness corrected contact angles are used especially when determining surface free energies.
Optical tensiometers are used to measure static, dynamic and roughness corrected contact angles. The main components of the optical tensiometer are a camera, a diffuser to disperse a drop, the sample tray and the light source to illuminate the droplet on the sample tray.
Our organization also provides contact angle measurement testing services with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.
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