ADHESION AND COHESION WORKING TOGETHER TO CREATE A STRONG BOND
Adhesive strength is the interfacial strength between adhesive and substrate, and usually the most important consideration when designing a strong adhesive bonded assembly. However, adhesive strength is not the only factor critical to creating an effective bond. Even when using the world’s toughest adhesive, a bond will fail if the adhesive does not bond to the surface of the substrate.
Cohesive strength is the internal strength of an adhesive – the ability of the adhesive to hold itself together under stress. The higher the cohesive strength, the stronger the adhesive. Cohesive strength is determined by the chemical composition of the adhesive.
It’s important to consider the specific types of stress that will act on an adhesive joint. Common stresses include shear, cleavage, peel and tensile (see our previous post on this). Knowing the magnitude and frequency of the stresses your application will be subjected to is helpful in choosing the adhesive with the best cohesive strength for the task at hand.