What is the term for when a sealant remains well bonded to both sides of a substrate, but fails in the middle?

When a sealant remains well bonded to both sides of a substrate but fails in the middle, the appropriate term to describe this scenario is cohesive failure. Cohesive failure occurs within the material itself rather than at the interface between the material and the substrate. This means that the sealant's integrity has been compromised internally, leading to a loss of structural integrity, while the adhesive bond to the surface remains intact.

Understanding this concept is crucial in firestop applications, where the continuity of material is essential for maintaining fire resistance. Identifying cohesive failure helps in determining the quality of the materials used and the effectiveness of the installation, ensuring that proper firestop measures are upheld.

In contrast, other types of failures, such as adhesive failure, occur at the bond line between the sealant and the substrate, while substrate failure refers to the underlying material being damaged rather than the sealant itself. Bond breaker failure is specific to situations where materials that are meant to be separated or not bonded together end up unintentionally adhering, which does not apply to the scenario described.