[Popular Science Knowledge] Analysis of the characteristics, advantages and disadvantages of epoxy resin glue

Epoxy resin adhesive generally refers to an adhesive made of epoxy resin as the main body. Epoxy resin adhesive should generally also include epoxy resin curing agent, otherwise the adhesive will not cure.
Epoxy resin adhesive is based on epoxy resin and its characteristics are reprocessed or modified to make its performance parameters meet specific requirements. Usually, epoxy resin adhesive also needs to be matched with curing agent before use, and needs to be mixed evenly before it can be completely cured. Generally, epoxy resin adhesive is called A glue or main agent, and curing agent is called B glue or curing agent (hardener).
1. Epoxy resin adhesive is divided into soft glue and hard glue
1. Epoxy resin soft glue: It is a liquid, two-component, soft self-drying soft glue, colorless, transparent, elastic, and will automatically restore its original shape when the surface is lightly scratched. Suitable for sign decoration of polyester, paper, plastic, etc.
2. Epoxy resin hard glue: It is a liquid, two-component hard glue, colorless and transparent, suitable for metal signs and can also make various high-end decorations such as crystal buttons, crystal bottle caps, crystal wooden combs, crystal crafts, etc.
2. Characteristics of epoxy resin glue
1. Basic characteristics: two-component glue, needs to be mixed with AB, has strong versatility, and can fill larger gaps
2. Operating environment: room temperature curing, indoors and outdoors, can be mixed manually or with AB glue special equipment (such as AB glue gun)
3. The applicable temperature is generally between -50 and +150 degrees
4. Suitable for general environment, waterproof, oil-resistant, strong acid and alkali-resistant
5. Place in a cool place away from direct sunlight, with a shelf life of 12 months
Epoxy resin glue is based on epoxy resin and its characteristics are reprocessed or modified to make its performance parameters meet specific requirements. Usually, epoxy resin glue also needs to be matched with a curing agent before use, and needs to be mixed evenly before it can be completely cured. Generally, epoxy resin glue is called A glue or main agent, and the curing agent is called B glue or curing agent (hardener).
The main properties of epoxy resin glue before curing include: color, viscosity, specific gravity, ratio, gel time, usable time, curing time, thixotropy (flow stop), hardness, surface tension, etc.
The main properties of epoxy resin glue after curing include: resistance, voltage resistance, water absorption, compressive strength, tensile (tension) strength, shear strength, peel strength, impact strength, heat deformation temperature, glass transition temperature, internal stress, chemical resistance, elongation, shrinkage coefficient, thermal conductivity, dielectric constant, weather resistance, aging resistance, etc.
III. Advantages of epoxy resin glue:
(1) Epoxy resin contains a variety of polar groups and highly active epoxy groups, so it has strong adhesion to various polar materials such as metal, glass, cement, wood, plastic, especially materials with high surface activity. At the same time, the cohesive strength of epoxy cured products is also very large, so its bonding strength is very high.
(2) Basically no low molecular volatiles are produced when epoxy resin is cured. The volume shrinkage of the adhesive layer is small, about 1% to 2%, which is one of the varieties with the smallest curing shrinkage among thermosetting resins. After adding fillers, it can be reduced to less than 0.2%. The linear expansion coefficient of epoxy cured products is also very small. Therefore, the internal stress is small and has little effect on the bonding strength. In addition, the creep of epoxy cured products is small, so the dimensional stability of the adhesive layer is good.
(3) There are many varieties of epoxy resins, curing agents and modifiers. Through reasonable and ingenious formula design, the adhesive can have the required processability (such as fast curing, room temperature curing, low temperature curing, curing in water, low viscosity, high viscosity, etc.) and 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, rubbers) and inorganic substances (such as fillers, etc.), and is easy to copolymerize, crosslink, blend, fill and other modifications to improve the performance of the adhesive layer.
(5) Good corrosion resistance and dielectric properties. It can resist corrosion from a variety of media such as acids, alkalis, salts, and solvents. The volume resistivity is 1013~1016Ω·cm, and the dielectric strength is 16-35kV/mm.
(6) General-purpose epoxy resins, curing agents, and additives are produced in many places, with large output, simple preparation, contact press molding, and large-scale application.
IV. Disadvantages of epoxy resin glue:
(1) When not toughened, the cured product is generally brittle, with poor peeling, cracking, and impact resistance.
(2) The adhesion to materials with low polarity (such as polyethylene, polypropylene, fluoroplastics, etc.) is low. Surface activation treatment must be performed first.
(3) Some raw materials such as active diluents and curing agents have varying degrees of toxicity and irritation. They should be avoided as much as possible when designing the formula, and ventilation and protection should be strengthened during construction operations.
5. Scope of application of epoxy resin glue
1. Epoxy resin glue is suitable for the anti-impact and wear, anti-cavitation and anti-freeze-thaw protection of the flow surface of hydraulic structures, as well as repair after damage;
2. Used for defect repair, reinforcement and reinforcement treatment of concrete buildings;
3. Epoxy resin glue is suitable for cracks in beams, columns, pile caps, etc. of buildings, honeycombs, holes and exposed steel bars on the surface of concrete structures;
4. Epoxy resin glue is suitable for anti-wear and repair of engineering parts such as runways, roads, bridges, tunnels, workshop mortar floors, etc.;
5. Suitable for bonding steel structures and concrete, and for leveling the bottom layer when bonding steel reinforcement and bonding carbon fiber reinforcement;
6. Used for protection and repair of concrete or metal components against acid, alkali and salt corrosion in chemical, petroleum, factories, docks, etc., sewage treatment pools, acid and alkali resistant floors, FRP anti-corrosion and other chemical anti-corrosion industries.
7. Epoxy resin glue is suitable for sealing, anti-corrosion and repair and reinforcement of interfaces such as underground pipelines, hydropower stations, and dam foundations.
8. Laying and caulking of granite, marble, acid-resistant tiles (boards), anti-corrosion of FRP lining of sewage pools, etc.
6. How to use epoxy resin glue
1. Use dry cotton cloth or sandpaper to remove dust, oil, rust, etc. on the bonding surface, and then wipe with cleaning agents such as acetone or trichloroethylene to clean the bonding surface.
2. Unscrew the front cover, take the weight ratio of A agent + B agent according to the above instructions, stir well and use it (A:B=2:1); in order to ensure the effect of use, it can also be used after vacuuming.
3. Note that it must be used up within the operable time, otherwise it will solidify, resulting in waste of materials. The highest strength can be obtained after 24 hours.
4. After applying the glue. Curing at room temperature for 2~6 hours and 40 degrees~50 degrees for 1~3 hours; use after 24 hours of application; the adhesion is better after ten days. On cold and humid days, it is better to bond at room temperature of 15~25 degrees.
5. When bonding straight or inverted surfaces, you must use adhesive paper to help stick after applying the glue, or use 502 glue to position. Epoxy resin glue formula Epoxy resin AB glue is a two-component high-temperature resistant adhesive based on epoxy resin, mainly suitable for bonding high-temperature resistant metals, ceramics, etc. Its operating temperature is -50~+180℃, and can reach +250℃ for a short time.
Epoxy resin glue needs more attention in use. It has a wide range of uses and is more delicate to operate. If it is operated well, the effect is more obvious.
Article source: Composite application technology
Original title: "[Popular Science Knowledge] Analysis of the characteristics and advantages and disadvantages of epoxy resin glue"