Adhesive knowledge

Common Term Adhesion
The surface of the two substances depends on chemical forces, physical forces, or a combination of both.
Adhesive
A substance that binds an adherend together by adhesion.
Structural adhesive
For adhesive bonding of stressed structures, adhesives that can withstand stress and environmental effects for long periods of time.
Primer
In order to improve the bonding performance, an adhesive is applied to the surface of the adherend before coating.
Curing
Adhesives are obtained through chemical reactions (polymerization, cross-linking, etc.) and improve the bonding strength and other properties.
Curing agent
A substance that directly participates in a chemical reaction and causes the adhesive to cure.

Adhesive strength index tensile strength
Under the action of the load perpendicular to the glue layer, when the glued sample is broken, the tensile force exerted on the glued surface of the unit.
Shear strength
Under the action of the load parallel to the glue layer, the shear force on the unit's adhesive surface when the glued sample is broken.
Peel strength
Under the specified peeling conditions, the unit width can withstand the impact strength (impact strength) when the bonded sample is separated.
The maximum work consumed by the unit's adhesive interface when the bonded sample is subjected to impact loading.
Modulus
Modulus is a mathematical quantity that describes the hardness of an object by measuring the length change or deviation of the object under load.

Adhesive Mechanism Mechanical Theory The mechanical theory believes that the adhesive must penetrate into the voids on the surface of the adherend and eliminate the air that is adsorbed on the surface of the adherend to produce a bonding effect.
Adsorption theory Adsorption theory believes that bonding is caused by the molecular contact between two materials and the generation of interfacial forces. The main source of adhesive force is intermolecular forces including hydrogen bonding forces and van der Waals forces.
Diffusion Theory Diffusion theory states that bonding occurs through the diffusion of molecules at the interface between the adhesive and the adherend.
Electrostatic theory produces electrostatic attraction due to the formation of double layers at the interface between the adhesive and the adherend, ie resistance to separation.
Weak Boundary Layer Theory The theory of weak boundary layers states that when the bond failure is considered as interface failure, it is actually a cohesive failure or weak boundary layer failure. The weak boundary layer comes from the adhesive, the adherend, the environment, or any combination of the three. If impurities are concentrated in the vicinity of the bonding interface and loosely bonded to the adherend, a weak boundary layer may appear inside the adhesive and the adherend.

The selection of adhesives is usually a major consideration in selecting adhesives: strength and durability requirements of bonded materials, adhesives, service requirements for adhesives, requirements for bonding processes, costs and other special considerations, etc. . The principle of choosing adhesives:

Consider the nature and hardness of the glue material;
Consider the shape and process conditions of the bonding material;
Consider the load and form (tensile force, shear force, peel force, etc.) of the bonded joints;
Consider the special requirements of materials such as electrical and thermal resistance and high temperature resistance.

Composition of adhesive

1. Adhesives: Also known as adhesives and adhesives, two or more adhesive materials that have been surface-treated are firmly joined together and have certain mechanical strength. For example, epoxy resin, copper phosphate phosphate, white latex, and the like.
2. Solid material (base material): Determine the main physico-chemical mechanical properties of the joint. For example, epoxy resin, phenolic resin, etc.
3, curing agent:
a) Curing: The process of changing the liquid adhesive into a solid by physicochemical methods. Physical methods include dissolution and volatilization, emulsion condensation, and melt cooling; chemical methods polymerize adhesives into macromolecules.
b) Curing Agents: Chemicals used in the curing process.
4, curing accelerator: can promote the curing reaction rate, shorten the reaction time of the chemical substances, also known as the catalyst.
5. Toughening agent: It can improve the toughness of the cured adhesive, mainly esters and elastic compounds.
6. Filler: It can improve the mechanical strength of the joint.
7, other auxiliary materials: colorants, solvents (diluents), antioxidants and coupling agents.

Source: 21st Century Fine Chemicals Network