Adhesive bonding technology is a widely used joining process. It relies on the physical adsorption force, chemical bonding force, and mechanical bonding force generated by the adhesive at the joint interface to firmly bond two components together. This process is simple and does not require complex equipment. Regarding how adhesives adhere to two substances, various theories have been proposed in the academic community. The most widely accepted theories include the mechanical theory and the adsorption theory.
The mechanical theory holds that the adhesive can penetrate into the tiny voids on the surface of the adherend and connect these surfaces through polymer chains. The adsorption theory, on the other hand, emphasizes that the molecular contact and interfacial forces between the two materials at the interface work together to produce the bonding effect.
Classification and Application
Polymer adhesives can be roughly divided into three categories according to their different chemical structures.
1. Epoxy resin: It has strong adhesion and does not blend with substances. It can be applied to electronic components.
2. Silicone rubber: It has good heat dissipation and is resistant to aging. It can be applied to high - temperature components.
3. Acrylate: It has stable properties and strong plasticity. It can be applied to small and precise components.
These adhesives are widely used in various fields due to their multiple properties such as high - temperature resistance, corrosion resistance, heat conduction, electrical conductivity, magnetic conductivity, and water resistance.
          In the aerospace field, the new strip - shaped epoxy resin foaming structural adhesive performs outstandingly. After heating, curing, and foaming reactions, it can fill the gaps between two substrates, achieving weight reduction, sealing, and mechanical property reinforcement. Compared with metal welding, foaming polymer adhesives are more widely used in the assembly and connection of the aerospace field due to their many excellent properties, such as ablation resistance, high - temperature resistance, low - temperature resistance, resistance to special media, resistance to the space environment, high - vacuum resistance, high strength, and high toughness.          In the biomedical field, medical adhesives are gradually replacing traditional suturing techniques. Medical adhesives can bond surgical incisions and wounds, reduce scar formation, and lower the risk of secondary trauma to patients during subsequent surgeries. For example, inspired by slugs, scientists at Harvard University have developed a double - layer hydrogel.
Through electrostatic interaction, covalent bonds, and physical penetration, it ensures the adhesion strength and is suitable for the adhesion of laparoscopic surgical wounds and the treatment of facial skin lacerations. In the field of electronic appliances, thermally conductive polymer materials make up for the deficiencies of metal materials in heat conduction. Polymer adhesives, such as silicone rubber binders and silicone rubber, have good heat resistance and can maintain the material stability and shape in high - temperature environments.
        Therefore, they are widely used in the thermal insulation, tube shell sealing, and semiconductor substrate bonding of thermistors. Compared with traditional adhesives, polymer adhesives exhibit more excellent physical and chemical properties and demonstrate great advantages and potential in practical applications. Humans have a long history of using adhesives, and in the application of adhesives, people continue to innovate and break through. In the future, more new high - performance adhesives will be integrated into people's daily lives.