ADHESIVES, GLUES AND SEALANTS
What is the surface energy and surface tension?
The surface energy is defined as the sum of all intermolecular forces that are on the surface of a material, the degree of attraction or repulsion force of a material surface exerts on another material.
In the case of liquids this same definition is applied to define the surface tension as a result of this surface tension liquid with low surface tends to contract and form droplets.
Surface tension can be defined as the resistance of a fluid to deform or break, such resistance is defined directly by the intermolecular forces that are on the liquid surface.
When the substrate has a high surface energy, ie it tends to attract, and the adhesive has a low surface tension, has little resistance to deformation or rupture, a good wetting of the adhesive on the substrate is produced.
For example, silicone adhesives have a low surface tension; this is the main reason why these adhesive bond on a wide range of substrates.
On the other hand, those substrates which contain silicone surfaces have a low surface energy and because of this reason, they are very difficult to get a good wettability and a good adhesion with any material unless you do a surface treatment to remove the silicone and increase surface energy of the substrate surface.
We can now find on the market, markers indicating a surface energy by marking or ink to the surface. This method gives us information about the state of the substrate, but it is not a method that ensures proper adhesion of an adhesive on a substrate.
Through the concept of surface energy it can be explained the working of Teflon non-stick, water-repellent effect, some anti-graffiti paints and plastics, easy to clean plastic slates with the use of non-marking pens, etc ...
Finally, the Young thermodynamic theory relationship adhesion with the contact angle and surface energy of the substrate by the following equation:
Ysv Wa = (1 + cos @)
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