Contact angle measurements are used to study the wettability of surfaces. This is especially useful in processes like coating and painting where good wettability is required to ensure good adhesion.
Wettability or wetting is the process that occurs when a liquid spreads and/or absorbs on a solid substrate or material. Wettability can be estimated by measuring the contact angle or by calculating the spreading coefficient.
https://youtu.be/Ea2iF2I3Q2M
The contact angle is the angle at which the liquid/solid/air interface meets the solid surface. When a liquid droplet is set onto a smooth homogeneous horizontal surface, it may spread out over substrate and the contact angle will approach zero if complete wetting takes place. Conversely, if wetting is partial, the resulting contact angle reaches equilibrium in the range of the material’s surface energy. The smaller the contact angle the greater the wettability or surface energy of the substrate is said to be. Contact angle is a good measure of surface wettability.
Wetting of a liquid on a solid surface depends on the solid surface properties as well as the liquid used. By manipulating the properties of surfaces (for example using plasma / corona surface treatment) the function or performance of a solid surface or material can be optimized for the purpose of interest.
Dyne Testing Ltd are the UK distributors for the Biolin Scientific Attension range of Optical and Force Tensiometers and will be demonstrating contact angle measurement during the Surface World Show taking place at the NEC, Birmingham at Stand 76 on Wednesday 23rd & Thursday 24th September 2015.