17.1 Introduction

For an adhesive or sealant bond to be useful, it not only must withstand the mechanical forces that are acting on it, but it must also resist the elements to which it is exposed during service. Thus, one of the most important characteristics of an adhesive joint or sealant is its endurance to the operating environment. This endurance is also referred to as the joint's permanence or durability. Strength and permanence are influenced by many common environmental elements. These include high and low temperatures, moisture or relative humidity, chemical fluids, and outdoor weathering. Table 17.1 summarizes the relative resistance of various adhesive types to common operating environments.