How does adhesive work?
From bonding metals, plastics and many other materials to gluing paper and wood, adhesives play a crucial role in countless industries, therefore it is important to know how does adhesive work. Adhesion and cohesion are the two fundamental principles that govern the adhesives’ behavior.
Adhesion
Adhesion is defined as the attraction between the adhesive and the surface of the material on which want to be bonded. This attraction occurs in a molecular level. Adhesive’s molecules interact with the molecules on the material’s surface. The strength of adhesion depends on various factors such as the type of adhesive, material’s properties etc.
Cohesion
Cohesion refers to the internal strength of the adhesive itself. Cohesion is responsible for keeping the adhesive together and preventing the adhesive from breaking apart.
The balance between adhesion and cohesion is extremely crucial to obtain a strong bond. Adhesives uses different types of bonds to adhere to materials.
Mechanical Bonds
Mechanical bonding is a simple version of adhesion. Adhesives can physically lock into microscopic pores and irregularities on the material’s surface. This mechanism is common in adhesive tapes used in rough surfaces.
Chemical Bonds
Chemical bonding is considered as the strongest form of bonding. Adhesives chemically bond with the material’s surface by physically changing the chemical structure of material’s surface. This bond can only exclusively occur when there are mutually reactive groups present in both adhesive and the surface it adheres to.
Electrostatic Bonds (Van der Waals Force)
Electrostatic bonds (aka adsorption) use electrostatic forces to adhere two materials. Adhesives like pressure-sensitive tapes and certain liquid adhesives rely on the Van der Waals force for bonding process. When you apply the adhesive, it generates numerous relatively weak electrostatic forces among the adhesive’s molecules and the those of the material’s surface it is applied on.