ABSTRACT
Sealing has been dened as “the art and science of preventing leaks” [1]. Sealants are used to seal joints and openings (gaps) between two or more substrates. The main purpose of a sealant is to prevent air, water, and other substances from entering or exiting a structure while permitting a certain amount of movement of the substrates. The distinction between sealants and adhesives is not always very clear. The primary function of sealants is to seal a joint, with adhesion and movement capability being important properties. Adhesives, on the other hand, are designed to hold materials together by surface attachment, often as alternatives to mechanical fastening systems. Thus, the primary function of adhesives is to transfer loads between adjacent surfaces, with adhesion and structural strength being important properties. Some materials are truly adhesive-sealants and fulll the dual role of bonding as well as sealing a joint. These materials often are also called structural sealants. All sealants must fulll three basic functions:
1. Sufciently ll the joint or gap to create an efcient seal 2. Form a barrier to gas or liquid ow 3. Maintain the seal in the operating environment (while permitting a certain
amount of movement of sealed parts)
It is known that people have used sealants and adhesive-sealants throughout history.
