Epoxy resin Epoxy resin is a kind of high molecular polymer, the molecular formula is (C11H12O3)n, which refers to the general name of a class of polymers containing more than two epoxy groups in the molecule. It is the polycondensation product of epichlorohydrin and bisphenol A or polyol. Due to the chemical activity of the epoxy group, a variety of compounds containing active hydrogen can be used to open the ring, cure and crosslink to form a network structure, so it is a thermosetting resin. Bisphenol A epoxy resin not only has the largest output and the most complete variety, but also the new modified varieties are still increasing and the quality is constantly improving.

material properties
Epoxy resins have secondary hydroxyl groups and epoxy groups, and the secondary hydroxyl groups can react with isocyanates. The epoxy resin is directly added to the hydroxyl-containing component of the polyurethane adhesive as a polyol. In this method, only the hydroxyl group participates in the reaction, and the epoxy group fails to react.

Use acid resin, carboxyl group to open epoxy ring, and then react with isocyanate in polyurethane adhesive. It is also possible to dissolve epoxy resin in ethyl acetate, add phosphoric acid for heating reaction, and its adduct is added to the polyurethane adhesive; the initial viscosity of the glue; heat resistance and hydrolysis stability can be improved. Alcohol amines can also be used. Or amines react to generate polyols, and the presence of tertiary nitrogen atoms in the adduct can accelerate the NCO reaction.

Using epoxy resin as polyhydroxy component combines the advantages of polyurethane and epoxy resin, and has good bonding strength and chemical resistance. The epoxy resin used in the manufacture of polyurethane adhesives generally adopts EP-12 and EP-13. , EP-16 and EP-20 varieties.

Modification method
1. Select the curing agent;

2. Add reactive diluent;

3. Add filler;

4. Add special thermosetting or thermoplastic resin;

5. Improve the epoxy resin itself.

Application field
Introduction

The excellent physical, mechanical and electrical insulation properties of epoxy resin, its bonding properties with various materials, and its flexibility of use process are not available in other thermosetting plastics. Therefore, it can be made into coatings, composite materials, casting materials, adhesives, molding materials and injection molding materials, and is widely used in various fields of the national economy.

Coating use
The application of epoxy resin in coatings accounts for a large proportion, and it can be made into varieties with different characteristics and uses. Its commonality:

1. Excellent chemical resistance, especially alkali resistance.

2. The paint film has strong adhesion, especially to metal.

3. Has good heat resistance and electrical insulation.

4. The paint film has good color retention.

However, the bisphenol A epoxy resin coating has poor weather resistance, and the paint film is easy to powder and lose its luster in the outdoors, so it is not suitable for outdoor coatings and high decorative coatings. Therefore, epoxy resin coatings are mainly used as anticorrosion paints, metal primers, and insulating paints, but coatings made of heterocyclic and alicyclic epoxy resins can be used outdoors.

Adhesive use
In addition to poor adhesion to non-polar plastics such as polyolefins, epoxy resins are also suitable for various metal materials such as aluminum, iron, copper; non-metallic materials such as glass, wood, concrete, etc.; and thermosetting plastics such as phenolic, amino , unsaturated polyester, etc. have excellent bonding properties, so it is called the universal glue. Epoxy adhesives are an important variety of structural adhesives.