Theories and Mechanisms of Adhesion

Abstract

Adhesion is an important attribute of material behavior that influences the interactions between different substances in the natural world, and it is also significant as this phenomenon is applied to the manufacture of man-made materials through applied adhesion, that is, adhesive bonding. Adhesive bonding is an important area of materials science focusing on the creation of joined substrates and composite materials. Because of the wide array of adhesive bonding situations, the concept of adhesion can be broadly applied across different material types and interactions. Mechanisms of adhesion fall into two broad areas: those that rely on mechanical interlocking or entanglement and those that rely on charge interactions. There are seven accepted mechanisms of adhesion. These are: mechanical interlocking or hooking theory; electronic, electrical double layer, or electrostatic theory; adsorption (thermodynamic) or wetting theory; diffusion theory; chemical (covalent) bonding theory; acid–base theory; theory of weak boundary layers. In addition, elastomeric-based adhesives exhibit a characteristic adhesion behavior described as tackiness or stickiness that aids in the creation of an almost instantaneous adhesive bond. This chapter provides an overview of adhesion theories and mechanisms and a short review of current research related to these topics.