A sealant may be viscous material that has little or no flow characteristics and which stay where they are applied; or they can be thin and runny so as to allow it to penetrate the substrate by means of capillary action.
Anaerobic acrylic sealants (generally referred to as impregnant) are the most desirable, as they are required to cure in the absence of air, unlike surface sealants that require air as part of the cure mechanism that changes state to become solid, once applied, and is used to prevent the penetration of air, gas, noise, dust, fire, smoke, or liquid from one location through a barrier into another.
Typically, sealants are used to close small openings that are difficult to shut with other materials, such as concrete, drywall, etc. Desirable properties of sealants include insolubility, corrosion resistance, and adhesion. Uses of sealants vary widely and sealants are used in many industries, for example, construction, automotive and aerospace industries.
Sealants can be categorized in accordance with varying criteria, e. g. in accordance with the reactivity of the product in the ready-to-use condition or on the basis of its mechanical behavior after installation.
Often the intended use or the chemical basis is used to classify sealants, too. A typical classification system for most commonly used sealants is shown below.
