It can be helpful to understand how adhesion works first on the smallest, molecular scale. A great and simple example is H20, commonly known of course as Water. At the same time we all know the two elements which make up water can exist on their own, independent of each other. Hydrogen and Oxygen.
By themselves each are normally* a gas with their own unique properties but start mixing them up in the right quantities and conditions (infill) and they adhere to each other and become “water”.
Individual tiny molecules in Love, ‘tis a beautiful thing.
Gather enough of them together and they collect (by the sextillions) in every droplet. All “adhering” to each other until acted upon by other forces.
The reason we quote “adhering” (above) is that they are actually exhibiting a force similar yet different from adhesion. The gathered water droplets are displaying “cohesion” where a substance, due to molecular properties sticks to itself.
This merely illustrates that adhesion is happening at some levels on the smallest scales measurable. The ways that modern adhesives work is very rich, however in different ways different substances work.
Most common glues work by combining a solvent (wetting agent) and a resin (hardening agent). By keeping your glue in a sealed container, the glue remains wet and pliable. In the case of a simple “paste” this might be water, in more modern adhesives a (moisture agent) is more likely a chemical derivative.
These glues commonly rely on surface porosity to create an interim bond between the materials. Filling the pores with a material that solidifies with as much cohesion as the two materials it is adhering (two pieces of wood or paper or various plastics).
Next Chapter – We will next study the balance between Adhesion and Cohesion and how those two concepts create more perfect adhesives for a plethora of purposes.
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