What are the different classifications of adhesive characteristics?

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Classification methods for adhesives vary widely, and currently, there is no unified classification standard both domestically and internationally. Based on the characteristics of adhesives, we can categorize them as follows:

1. Natural Adhesives vs. Synthetic Adhesives:

Natural adhesives are primarily composed of raw materials sourced from nature, such as animal glue, starch, dextrin, and natural rubber. On the other hand, synthetic adhesives are formulated using synthetic resins or synthetic rubber as the main ingredients, including epoxy resins, phenolic resins, chloroprene rubber, and nitrile rubber.

2. General-Purpose Adhesives vs. Specialized Adhesives:

Adhesives can be further classified as general-purpose adhesives and specialized adhesives. Specialized adhesives are designed for specific applications and can be further categorized based on their suitability for metals, wood, glass, ceramics, rubber, polyethylene foam, and other materials.

3. Structural Adhesives vs. Non-Structural Adhesives:

Adhesives can be categorized based on their bonding strength as structural adhesives and non-structural adhesives. Structural adhesives are capable of withstanding significant stress, regardless of the bonding position. These adhesives typically have a shear strength of up to 7 MPa under static loads and exhibit good resistance to uneven peel strength and fatigue. Non-structural adhesives, on the other hand, are not designed to bear substantial loads and are primarily used for bonding smaller parts or temporary fixation during assembly work.

4. Curing Temperature:

Adhesives can be classified based on their curing temperature as room-temperature curing adhesives, medium-temperature curing adhesives, and high-temperature curing adhesives. Room temperature curing adhesives solidify at temperatures below 30°C. Medium-temperature curing adhesives solidify within the range of 30-99°C. High-temperature curing adhesives, as the name suggests, require temperatures above 100°C for curing.

5. Thermoplastic Adhesives vs. Thermo-setting Adhesives:

Adhesives can be further categorized based on the characteristics of the adhesive layer after curing. Thermoplastic adhesives have a linear structure and can be cured through processes such as solvent evaporation, melt cooling, or emulsion coagulation. The adhesive layer of thermoplastic adhesives softens when heated and is soluble in solvents. They generally exhibit lower cohesive strength and poorer heat resistance. In contrast, thermo-setting adhesives have a cross-linked structure and do not soften when heated. They are insoluble in solvents and exhibit higher cohesive strength. They also offer heat resistance, resistance to media corrosion, and resistance to creep. However, thermo-setting adhesives may have lower impact strength and peel strength.

6. Base Materials:

Adhesives can be classified based on their base materials, including resin-based adhesives, rubber-based adhesives, inorganic adhesives, and natural adhesives, among others.

7. Special Performance:

Adhesives can also be classified based on their special properties, such as conductive adhesives, magnetic adhesives, and spot welding adhesives. To facilitate the infiltration of adhesives into the adhered surface, adhesives need to be in a liquid state or transformed into a liquid state before bonding. Only after curing, the adhesive achieves its strength. The process of transforming the adhesive layer from a liquid state to a solid state is known as curing. Different adhesives employ different curing methods.

In summary, the classification of adhesives can be based on their origin, purpose, bonding strength, curing temperature, adhesive layer characteristics, and base materials. Adhesives can be classified as natural or synthetic based on the origin of their raw materials. Natural adhesives derive their components from natural sources, while synthetic adhesives are formulated using synthetic resins or rubber.

Additionally, adhesives can be categorized as general-purpose or specialized based on their intended applications. Specialized adhesives are further divided into various types according to their suitability for specific materials like metals, wood, glass, ceramics, rubber, or polyethylene foam.