When using a caulk and sealant, you can often see the end result, but may not understand what its cause was. Below are a few terms from our glossary to help explain what can sometimes occur when you’re using a caulk or sealant.

 

Polymerization

The interlocking of molecules by chemical reaction to produce larger molecules. (A combo of monomers are polymerized to produce a polymer, the base emulsion for a given caulk/sealant, paint or coating.

 

Adhesive Failure

Loss of adhesion between the adhesive & substrate. The adhesive pulls cleanly away from the substrate. In a sealant joint, failure between the sealant & the substrate.

 

Cohesive Failure

This type of failure occurs when the sealant cracks down the middle (or somewhat off-center), while the adhesion of the sealant on both sides of the joint is maintained. If failure is unavoidable (such as when large joint movement occurs), cohesive failure is the most desirable failure mode. The reason is that usually this type of failure does not require that the failed sealant be removed; only that it be cleaned well & resealed w/ fresh material of the same type.

 

Cure

The process by which a semi-liquid sealant/adhesive becomes a firm, functional solid. (A) Latex systems cure by evaporation/coalescence; whereby as the water evaporates from the system the particles of polymer binder come closer & closer together until they touch and coalesce together, forming a continuous film. (B) Chemically curing systems (silicone, polyurethanes, polysulfide, etc. function by using highly reactive chemical components of simple chemical structure that interact to form complex polymers in place. (C) Oil-based caulks rely on the slow process of air oxidation to cause vegetable oils to polymerize in place.

 

Elongation

The ratio of the change in length of a stretched sample to the original length of the sample (measured in per count), usually the ultimate value (elongation @ failure.) (extension produced by a tensile stress)

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