TABLE OF CONTENTS Adhesives unite materials, creating a whole that is greater than the sum of its parts (Skeist and Miron, 1977). Their volume is small compared to the metals, glass, wood, paper, fibers, rubber, and plastics they bond. The "adhesive" bonds "adher-ends," which are substrates such as glass, metal, plastics, and wood (Dann, 1970).
In a typical adhesive bond, the basic components are:
SUBSTRATE/INTERFACE /ADHESIVE/INTERFACE/SUBSTRATE
Adhesives may be classified in many ways including mode of application and setting, chemical composition, cost, suitability for various adherends, and end products. Chemical composition will be the preferred method of classification as the theme of this book is "analysis of adhesives," but other methods related to formulating will be discussed for the reader's information.
Adhesives must be applied to substrates in a fluid form to wet the surfaces, which requires low viscosity to flow onto the surfaces while eliminating voids. After application to surfaces (adherends), the adhesive must solidify to develop bonding strength. The transition from fluid to solid may be accomplished in the following ways (Skeist and Miron, 1977):
Cooling of a thermoplastic. Thermoplastics soften and melt when heated, becoming hard again when cooled. Methods of applying adhesives in this way include hot-melt applicators; dry powders that are heated after application; andextruders.
Release of solvent or carrier. Solutions and latices contain the adhesive composition in admixture with water or organic solvents. These liquids lower the viscosity to permit wetting of the substrate. After wetting has been accomplished, they must be...
