The adhesive can bond well with two kinds of different materials are not the same, because they have adhesion, cohesion and cohesion is composed of adhesion between the adhesive and adherend by the adhesive layer, is the role of the two forces, the loss of any one of them is force. The adhesive will lead to loss and damage.
Cohesive force is the force of adhesive itself between molecules, which is composed of basic components, factors of adhesive with various additives and formulation, process and environment, decided in the test specimen in shear bond failure, when the cohesive failure, must be the cohesive force of the adhesive is caused by adhesion force is less than. Damage occurred in the adhesive layer, which is in two pieces of specimens are damaged surface with a layer of adhesive, and then glue the rough surface, and measuring effective cohesive force of the adhesive and cohesive force in addition to its bonding area have the cohesive strength of the adhesive.
The adhesion force between is adhesive and adherend, when the bonding part tensile or shear test, if the cohesion is greater than the adhesion force and adhesion failure occurs, then the sample is destroyed along the interface bonding layer, the sample surface finish is destroyed, there is no glue in a sample, exposed material the surface, while another sample with adhesive test in this case that the adhesion force.