Adhesion (adhesion): refers to the state where two surfaces are joined together by chemical force, physical force or both.
The adhesive must first adhere to the surface of the adherend. This is due to the adhesion between the two phases, which is derived from the secondary bond force or the primary bond force.
Cohesion: the state where the particles within a single substance are joined together by the primary valence bond force (including ionic bond, covalent bond, coordination bond, metal bond, etc.) and secondary bond force (including van der Waals force, hydrogen bond). The cohesion of the adhesive is related to the intermolecular force, relative molecular mass, degree of cross-linking, crystallization and molecular entanglement.
Adhesive requirements:
1: Regardless of the state, it should be liquid when applied.
2: The surface of the adherend can be completely spread and fully wetted.
3: It must be able to transform the liquid into a solid or gel state in some way to form a tough and stable glue layer.
4: It should have a certain strength after curing. It can be connected reliably, transfer stress, and resist damage.
5: It can withstand temperatures above 0°C and stand the test of a certain period of time.
