What are the characteristics of epoxy resins?

2023.2.15 Articles GOTREND Technology Co.,Ltd

GOTREND article-What are the characteristics of epoxy resins?
Epoxy resin is a kind of polymer, which refers to a class of polymers containing more than two epoxy groups in the molecule. 

Epoxy resin is widely used, here is mainly for a common use of fixation, bonding, potting, insulation and other epoxy resin glue in the GOTREND core components to illustrate, that is, epoxy resin adhesive, is also an indispensable packaging insulation material in the electronics industry.

1.What is epoxy adhesive? 
Epoxy adhesives are a class of engineering adhesives formulated from epoxy binders, curing agents, thinners, accelerators and fillers. 
Because of its good bonding performance, good functionality, relatively low price and simple bonding process, it has been widely used in the fields of home appliances, automobiles, water conservancy transportation, electronic appliances and aerospace industry in recent decades. 

With the continuous development of high-tech and nanotechnology, in recent years, the modification of epoxy resin has been deepened, interpenetrating networks, chemical copolymerization and nanoparticles.

2. Advantages and disadvantages of relevant composition and characteristic characteristics 
2.1 Composition : 
Epoxy resin adhesive is composed of epoxy resin, curing agent, plasticizer, accelerator, diluent, filler, coupling agent, flame retardant, stabilizer, etc. 
Among them, epoxy resin, curing agent, and flexibilizer are indispensable components, and others are decided to be added according to needs.

2.2 Feature principle : 
Epoxy adhesives are liquid or solid adhesives composed of epoxy resin, curing agent, accelerator, modifier, thinner, filler, etc. The adhesive process of epoxy adhesive is a complex physical and chemical process, including infiltration, adhesion, curing and other steps, and finally generating a cured product with a three-dimensional cross-linked structure, which combines the adhered matter into a whole.

Bonding properties (strength, heat resistance, corrosion resistance, impermeability, etc.) not only depend on the structure and properties of the adhesive and the structure and adhesive characteristics of the surface to be glued, but also closely related to the joint design, the preparation and storage of the adhesive and the bonding process, etc., and are also constrained by the surrounding environment (stress, temperature, humidity, medium, etc.).

Therefore, the application of epoxy adhesives is a system engineering. The properties of epoxy adhesives must be adapted to the factors described above that affect the bonding properties for optimal results. 
The performance of using epoxy adhesives of the same formulation to glue objects of different properties, or using different bonding conditions, or in different use environments, will be very different.

2.3 Compared with other types of adhesives, epoxy adhesives have the following advantages : 
(1) Epoxy resin contains a variety of polar groups and epoxy groups with great activity, so it has strong adhesion with metals, glass, hardware, magnetic cores, plastics and other polar materials, especially materials with high surface activity, and the cohesive strength of epoxy cured products is also very large, so its bonding strength is very high.

(2) When epoxy resin is cured, there is basically no low molecular volatiles produced. 
The volume shrinkage of the adhesive layer is small, about 1%~2%, which is one of the varieties with the smallest curing shrinkage in thermosetting resins. After adding filler, it can be reduced to less than 0.2%. The linear expansion coefficient of epoxy solids is also small. 
Therefore, the internal stress is small, and the influence on the bonding strength is small. In addition, the creep of the epoxy cured product is small, so the dimensional stability of the adhesive layer is good.

(3) There are many varieties of epoxy resin, curing agent and modifier, and the adhesive can have the required processability (such as fast curing, room temperature curing, low temperature curing, low viscosity and high viscosity, etc.) through reasonable and ingenious formula design, and has the required performance (such as high temperature resistance, low temperature resistance, high strength, high flexibility, aging resistance, electrical conductivity, magnetic conductivity, thermal conductivity, etc.).

(4) It has good compatibility and reactivity with a variety of organic substances (monomers, resins, rubber) and inorganic substances (such as fillers, etc.), and is easy to carry out copolymerization, crosslinking, blending, filling and other modifications to improve the performance of the rubber layer.

(5) Good corrosion resistance and dielectric properties. It can resist the corrosion of acid, alkali, salt, solvent and other media. Volume resistivity 1013~1016Ω·cm, dielectric strength 16~35kV/mm. 

(6) General-purpose epoxy resin, curing agent and additives have many origins, large output, simple preparation, contact compression molding, and large-scale application.

2.4 The main disadvantages of epoxy adhesives : 
(1) When it isn’t toughened, the cured product is generally brittle, and the resistance to peeling, cracking and impact resistance is poor.

(2) The adhesion to materials with low polarity (such as polyethylene, polypropylene, fluoroplastics, etc.) is small. Surface activation must be performed first. 

(3) Some raw materials such as reactive diluents, curing agents, etc. have different degrees of toxicity and irritation. When designing the formula, the selection should be avoided as much as possible, and the ventilation and protection should be strengthened during the construction operation.


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