Sealants are generally chosen for their ability to fill gaps, resist relative movement of the substrates, and exclude or contain another material. Sealants are generally lower in strength than adhesives, but have better flexibility. Usually, a sealant must effectively bond to a substrate in order to perform these functions.
Sealants are like adhesives in many ways. If fact, they are often considered together because some formulations can perform as either an adhesive or as a sealant, and some formulations actually provide both functions. Sealants, however, must perform distinctive tasks that stand them in a separate category from adhesives. It is important that the sealant formulator recognizes and supplies to these functional needs.
This article will review the special functions required of sealants. The methods by which the sealant performs these functions will be reviewed. Specifically, the application and performance characteristics of sealants will be addressed and correlated to the composition of the sealant formulation.