Phenolic resin, usually refers to the polymerization of phenol and formaldehyde under the action of a catalyst polymer. These resins were the first thermosetting resins to be synthesized. According to their structure and properties, phenolic resins can be divided into different types, including linear phenolic resins, thermosetting phenolic resins and oil soluble phenolic resins. Phenolic resin has excellent acid resistance, mechanical properties, heat resistance and other characteristics, so it has a wide range of applications in the manufacture of varnishes, insulating materials, corrosion resistant coatings and other fields. Among them, one of the most notable characteristics of phenolic resin is its excellent high temperature resistance. The phenolic resin retains its structural integrity and dimensional stability even under extreme high temperature conditions. In addition, phenolic resin can be dissolved in ethanol, acetone and other solvents, and has solubility and fusible. Curing (curing rapidly when heated) occurs only when a crosslinking agent, such as hexamethylenetetramine or polyformaldehyde, is introduced. When cross-linked, phenolic resin resists attack by a variety of chemicals, including gasoline, petroleum, alcohols, glycols, and various hydrocarbons.

Phenolic resin is a kind of important polymer material, its synthesis and application fields are wide. In this paper, the synthetic curing methods, properties and different types of applications of phenolic resin are discussed.

Synthesis, curing and application analysis of phenolic resin

Synthesis and curing of phenolic resin
The synthesis and curing process of phenolic resin follow the law of polycondensation reaction. By controlling different synthesis conditions, such as the ratio of phenol to aldehyde and the type of catalyst, two types of phenolic resin can be obtained: thermosetting phenolic resin and thermoplastic phenolic resin.

Thermosetting phenolic resin

Thermosetting phenolic resins include resins with further reactive hydroxymethyl active groups. In the synthesis process, if no special control is carried out, the bulk polycondensation reaction will be carried out to form a non-melting and insoluble cured resin with a three-way network structure. The paint film of thermosetting phenolic resin is quite hard after baking, has excellent moisture resistance, insulation properties, and is suitable for a variety of applications, such as glued laminates.

Thermoplastic phenolic resin

Unlike thermosetting phenolic resins, thermoplastic phenolic resins are linear and do not form a three-way network structure during synthesis, so curing agents need to be added during further curing. The synthesis and curing principles of these two types of resins are different, so their molecular structures are also different.

Synthesis, curing and application analysis of phenolic resin

According to the different degree of reaction, phenolic resin can be divided into a class resin, B class resin and C class resin. A stage resin is a synthetic resin primary product, can appear liquid, semi-solid or solid state, after heat can quickly melt. After further heating, the intermolecular reaction of B-stage resin will lead to crosslinking, and its molecular structure is more complex than that of meltable phenolic resin, and the paint film is harder. C-stage resin is the product of a deeper cross-linking reaction, has a complex network structure, and becomes a non-melting resin, its properties and uses are also different.

Synthesis, curing and application analysis of phenolic resin

Application of phenolic resin
Phenolic resin is widely used in the field of coatings, mainly including alcohol-soluble pure phenolic resin paint, rosin modified phenolic resin paint and oil-soluble pure phenolic resin paint.

Alcohol-soluble phenolic resin paint

This paint is divided into thermoplastic and thermoset. Thermoplastic alcohol-soluble phenolic resin paint is a volatile self-drying paint with a faster drying speed. It has excellent resistance to acid, organic solvents and acid gases, and low toxicity. However, its paint film is easy to become brittle, prone to reddening in sunlight, and the heat resistance temperature is limited. Compared with the thermosetting phenolic resin paint, its application field is narrow.

Modified phenolic resin paint

Rosin modified phenolic resin paint is one of the most widely used types. The paint film formed by it and tung oil has the characteristics of high hardness, good drying, good chemical corrosion resistance and low price, but the paint film is easy to yellow. This paint is widely used in wood furniture, construction, ships, insulation materials and fine arts.

Synthesis, curing and application analysis of phenolic resin

Oil soluble pure phenolic resin paint

It is divided into two kinds: non-oil reaction type and oil reaction type resin paint. These coatings have better adhesion, excellent durability and wear resistance, and a high degree of moisture resistance. Phenolic resin paints play an important role in different fields, providing a variety of options for wood finishes, insulation materials, coatings, etc. By adjusting different types of phenolic resin paints, it can meet the needs of various applications and promote the development of modern industry.

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In the entire field of phenolic resins, there are not only rich application prospects, but also extensive research and development opportunities to meet the growing market demand and innovation challenges. Continued research into phenolic resins will help us better understand their properties and applications, driving progress in the field of materials science.