7.1 Introduction to Adhesives

Adhesives were first used many thousands of years ago, and most were derived from naturally occurring vegetable, animal, or mineral substances. Synthetic polymeric adhesives displaced many of these early products due to stronger adhesion and greater resistance to operating environments. These modern plastic and elastomer based adhesives are the principal subject of this chapter.

An adhesive is a substance capable of holding substrates (adherends) together by surface attachment. A material merely conforming to this definition does not necessarily ensure success in an assembly process. For an adhesive to be useful, it must not only hold materials together but also withstand operating loads and last the life of the product.

The successful application of an adhesive depends on many factors. Anyone using an adhesive faces a complex task of selecting the proper adhesive and the correct processing conditions that allow a bond to form. One must also determine the substrate-surface treatment which will permit an acceptable degree of permanence and bond strength. The adhesive joint must be correctly designed to avoid stresses within the joint that could cause premature failure. Also, the physical and chemical stability of the bond must be forecast with relation to its service environment. This chapter is intended to guide the adhesives user through these numerous considerations.