Nature of Adherends

The surfaces of adherends are pretreated before applying adhesives. Wood or metal adherend surfaces are leveled to provide fine and true plain surfaces so that proper joining by using a thin adhesive film can be achieved. Plastic adherend surfaces are pressed under high temperature and pressure to achieve proper bonding. Sometimes, sand blasting may be required. To remove the organic materials and increase specific adhesion, the metals may be treated chemically by immersing it in an acid or alkali bath. Similarly, specific solvent treatment may be given to wood surfaces.

Composition of Adhesives

The important components of an adhesive are thinner made up of oil and water, additives and fillers made up of powder aluminum oxide, extenders made up of urea, formaldehydes vinyl, and silicone, plasticizers and hardeners made up of thermoplastics and polyesters. These compositions may vary for each job to obtain uniform contact over the adherend surfaces. You can apply the adhesives uniformly over the adhesive surfaces in the following ways:

• By brushing: Adhesives can be applied to the surface simply by using a brush.

• By roller coating: Adhesives are applied to the surface and it is then spread on the surface with the help of a roller.

• By spraying: Adhesives are...