Properties of Adhesives
This handbook contains information about the classification, types, form, properties, bonding process of adhesives.
TABLE OF CONTENTS Properties of Adhesives
Adhesive Action
Some chemical or physical forces of attraction are responsible for holding material by adhesion. These forces are called specific adhesion. The adhesives are applied on the surface of the adherent, establishing contact in molecular dimensions. For permanent adhesion, the interfacial boundary energy of the adhesive and the adherend surfaces must be lower than the sum of the surface energies of the adhesive and the adherends.
The adhesive may fill the voids or pores of rough surfaces and hold the surfaces by interlocking action. This action is known as mechanical adhesion. When the surfaces in the adhesive dissolve, resulting in the bonding of surfaces, it is known as fusion adhesion.
Development of Adhesive Strength
Adhesives penetrate the pores of the adherends and it binds to the surface after drying. As a result, the pieces are fastened together by the strength of the adherend and the strength of the adhesive. Adhesive strength develops in the following four methods.
Chemical Reaction
Generally, cross-linked adhesives, such as phenol formaldehyde and urea formaldehyde resins have greater strength. It can be achieved when the ingredients of thermosetting adhesive materials are treated together during the curing and cross-linking processes.
Applying Pressure
Greater bond strength can be developed instantaneously by applying high pressure on highly viscous and pressure-sensitive adhesives.
Loss of Solvent
After the dispersion of adhesives, water is applied to the surfaces of adherends and the two adherends are brought in contact with each other. The solvent either evaporates or enters into the pores of...
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