Why we Measure Contact Angle
HITAS have also been getting to grips with our Contact Angle Geniometer to help gain knowledge of how our surfactant formulations aid in the spreadability of water and liquid products. Along with our Surface Tensiometer, this piece of equipment is very useful for the product development process, as it can give us a great idea of which raw materials will have the biggest influence on surface wetting and spreadability.
Measuring contact angle is useful as it can be used to predict how well a surfactant/wetting agent will allow a liquid to wet and spread on a surface, whether that be on soil or a leaf. We combine this with the various other tests we perform on all our new formulations, to determine which products are best suited to a given application. This method is particularly useful when investigating potential adjuvants and spreading agents.
How we Measure Contact Angle
The Contact Angle Geniometer can be used to determine surface free energy, by evaluating the interface of a liquid on a solid surface. When a drop of liquid is placed on a surface, it will form a dome shape. The angle that is formed between the surface and a line tangent drawn to the edge of the droplet is called the contact angle. The Geniometer can be used to capture a photo or video of the droplet, and the measurements can be taken from a still image or for a droplet as it spreads over time.
As a drop of liquid spreads across a surface, the dome shape will become flatter, resulting in a smaller contact angle. Water does not spread well because the attractive forces water has for itself are greater than the attractive forces between it and the surface. This means that a water droplet will form a shape as close to a sphere as it can, giving a high contact angle.
Chemicals, such as surfactants, can be added to water to reduce the attraction water molecules have for each other and allow them to spread out on a surface. By determining the contact angle produced when different chemicals are added to water, we can evaluate the effectiveness of different raw materials and formulations. Effects on spreadability over time can be used to determine how well a product will allow applied liquids to spread on a surface in the field.