What can lead to cohesive failure in an adhesive bond?

Cohesive failure in an adhesive bond occurs when the internal structure of the adhesive material itself fails rather than the bond between the adhesive and the substrates. This type of failure is primarily influenced by inherent material weaknesses in the adhesive, such as low bond strength, inadequate curing, or poor quality of the adhesive itself. When the adhesive lacks sufficient structural integrity to withstand the forces applied, it will break down internally, leading to a cohesive failure.

For instance, if an adhesive is not formulated to have the required mechanical properties for a specific application, it may be prone to failure when subjected to stress. Similarly, if the adhesive has aged over time or has been mixed improperly, its performance can be compromised, resulting in cohesive failure.

Other factors, such as surface preparation and environmental conditions, can influence adhesive performance but typically lead to adhesive failure (where the bond separates at the interface) rather than cohesive failure. Inappropriate surface preparation can prevent adequate bonding, while extremes in temperature or moisture can impact the adhesive's performance but do not directly pertain to the material's inherent weaknesses.