What Is Epoxy Resin Material?

What is epoxy resin material?

Epoxy resin, also known as EP resin, artificial resin or resin glue, is a polymer compound containing at least two epoxy groups in the molecule, which when reacted with a curing agent forms a thermosetting three-dimensional mesh structure. Epoxy resins are thermosetting plastics with excellent physical and mechanical properties, and are used in a wide range of applications such as adhesives, coatings, electronic packaging, printed circuit boards, construction materials, aerospace, and military industries. The IUPAC name for the epoxy group is ethylene oxide (oxirane), and the prepolymer and cross-linking product can also be collectively referred to as epoxy resin.

Epoxy resins can react with themselves (cross-linking) through catalytic homopolymerization, or with a variety of co-reactants including polyfunctional amines, acids (anhydrides), phenols, alcohols and mercaptans. These co-reactants are often referred to as hardeners or curing agents, and the cross-linking reaction is often referred to as curing.

Origin of epoxy resins

In 1934, German chemist Paul Schlack first patented the condensation reaction of epoxides with amines. Then in 1943, Dr. Pierre Castan announced the discovery of epoxy resins based on bisphenol A. This research was eventually licensed by the Swiss company Ciba, which became one of the world's leading producers of epoxy resins, and in 1946, Sylvain Greenlee patented an invention for a resin made from the cross-linking of bisphenol A and epichlorohydrin during his time with the DeVoe and Reynolds companies.

China's development of epoxy resins began in 1956 and was first successful in Shenyang and Shanghai. By the end of the 70s, China had formed a complete industrial system from monomer, resin, auxiliary materials, from scientific research, production to application.

Bisphenol A epoxy resin

About 75% of the epoxy resins used worldwide are based on the reaction of bisphenol A with epichlorohydrin (ECH) to produce bisphenol A diglycidyl ether (BADGE or DGEBA).

This production process is a two-stage process in which epichlorohydrin is first added to bisphenol A to form bisphenol A bis(3-chloro-2-hydroxypropyl) ether, which then undergoes a condensation reaction with an equal amount of sodium hydroxide to form a double epoxide. The chlorine atoms are released as sodium chloride and the hydrogen atoms are released as water. When the formed epoxide is further reacted with bisphenol A, higher molecular weight diglycidyl ethers (n ≥ 1) are formed:

By controlling the number of molecular units, different forms of epoxy resins can be obtained. Fewer molecular units (n = 1~2) result in viscous, transparent liquid epoxy resins. A larger number of molecular units (n = 2 to 30) results in colorless solid epoxy resins. Although bisphenol A-based epoxy resins are the most common products on the market, other bisphenols, such as bisphenol F (BPF), can react similarly with epichlorohydrin.

Bisphenol A diglycidyl ether further reacts with bisphenol A to produce a higher molecular weight diglycidyl ether (n≥1) called prepolymerization. The product consisting of repeating units (n=1~2) is a viscous clear liquid called liquid epoxy resin. The product consisting of repeating units (n=2~30) is then a colorless solid called solid epoxy resin.

Bisphenols other than bisphenol A (especially bisphenol F) or brominated bisphenols (e.g., tetrabromobisphenol A) can also be used for the epoxidation and prepolymerization described above. Compared to Bisphenol A resins, resins such as Bisphenol F and Bisphenol H usually have a lower viscosity and a higher average epoxy content per gram, resulting in better chemical resistance after curing.

Since epoxy resins exist as polymers, semipolymers, or oligomers, they are seldom found as pure substances. Higher purity grades of epoxy resins can be obtained in specific applications, e.g. by using distillation purification processes. However, high purity liquid epoxy resins tend to form crystalline solids due to their highly regular structure and therefore need to be melted in order to be processed.

One of the most important indicators of an epoxy resin is the epoxy value, which represents the content of epoxy groups. The epoxy value is expressed as “epoxy equivalent weight”, i.e. the ratio between the molecular weight and the number of epoxy groups. This parameter is used to calculate the amount of curing agent required during the curing process. Epoxy resins are usually cured with stoichiometric or near stoichiometric curing agents in order to obtain the best physical properties.

Epoxy Resin Applications

Epoxy resin excellent electrical insulation, physical and mechanical properties, and a variety of materials bonding properties, as well as the flexibility of its use of technology is not available in other thermosetting plastics. Therefore, it is widely used in: coatings and adhesives; mold casting of various electronic devices, integrated circuits, packaging materials and circuit boards; the manufacture of industrial parts products; waterproofing materials; building structural reinforcement reinforcement, can be used with carbon fibers to become a very high tensile strength of the reinforcement material.

• Building material

Epoxy resins have been researched and applied in the field of construction for decades, and have excellent adhesive properties for various construction materials, with high strength, fatigue resistance, aging resistance, corrosion resistance, etc. Epoxy resins can be used as additives to enhance the mechanical properties of mortar and concrete. Epoxy resin can be used as an additive to enhance the mechanical properties of mortar and concrete; modified epoxy resin can be used for the reinforcement of concrete structure, such as paste carbon fiber cloth reinforcement, paste steel plate reinforcement, planting reinforcement, repair of cracks and defects in concrete, etc., and it is also the first choice of structural adhesive material recognized in the industry.

• Adhesive

Epoxy adhesives are a major part of the “structural” or “engineered adhesives” category, which also includes polyurethanes, acrylics, cyanoacrylates, and others. These high-performance adhesives are used in the manufacture of airplanes, automobiles, bicycles, boats, golf clubs, skis, and other applications that require high-strength bonds. Epoxy adhesives can bond virtually any material, providing excellent adhesion to wood, metal, glass, stone and plastics, and can be made flexible or rigid, transparent or opaque, colored, fast-setting or slow-setting, as required. Epoxy adhesives are significantly better than other types of adhesives in terms of heat and chemical resistance.

• Electrical and electronic equipment

Epoxy plastic sealants and chip grade electronic adhesives play a key role in the electronics industry, and are critical materials to ensure the stable realization of chip functions, greatly affecting the quality of semiconductor devices. It is often used in electric motors, generators, transformers, switchgear, printed circuit boards and semiconductor packages. Epoxy resins are excellent electrical insulators, protecting electrical components from short circuits, dust and moisture. In the electronics industry, epoxy resins are used in the overmolding of integrated circuits, transistors and hybrid integrated circuits and in the manufacture of printed circuit boards. The largest circuit board type, FR-4, consists of prepared fiberglass cloth with fire-resistant epoxy resin. Since the encapsulated semiconductor device needs to be able to withstand lead-free reflow soldering at 260 °C even after high temperature and high humidity treatment, and the encapsulated material is required to be free from delamination or cracking and electrical failure due to excessive stress during the process, a wide range of physicochemical properties (flow length, coefficient of thermal expansion, glass transition temperature, viscosity, water absorption, and dielectric constant) need to be passed to achieve the process performance as well as application performance requirements.

• Wind power generation

Epoxy splicing adhesive can be used for wind turbine tower precast concrete section installation splicing, with epoxy resin material excellent concrete bonding performance, can produce lower cost, better durability of the wind turbine; epoxy resin and glass fiber or carbon fiber fabric combination, can produce very high strength and light weight composite materials, these materials are very suitable for the manufacture of longer, more efficient wind turbine rotor blades; Epoxy resins can also be used as protective coatings for steel towers, pedestal struts and concrete foundations, extending equipment life and reducing maintenance costs. Generators are connected to the rotor blades by a drive train that converts mechanical wind energy into usable electricity, a process that requires the electrical insulation and high heat resistance of epoxy resins. In addition, epoxy resins are used in transformers, bushings and composite cables connecting wind turbines to the grid. Currently, wind energy components in Europe represent the largest segment of epoxy resin applications, with a share of about 27% of the market.

• Aerospace

In the aerospace industry, epoxy resins are excellent reaction-curing materials that, when compounded with high-performance fiber-reinforced materials, become irreplaceable structural matrix materials. Typical fiber reinforcing materials include glass fibers, carbon fibers, Kevlar fibers and boron fibers. Epoxy resins are also used as aerospace structural adhesives and are superior to most other types of resins in terms of mechanical properties and resistance to environmental attack.

Researchers have found that a composite coating made of graphene and epoxy resin on the rotor blades of aircraft wings can effectively de-ice, and experiments have shown that the coating can still melt the centimeter-thick ice on the rotor blades of the wings under the environmental conditions of -20°C. The method belongs to the active anti-icing system, which is more environmentally friendly than the chemical anti-icing method. This method belongs to the active anti-icing method in the de-icing system, which is more environmentally friendly than the chemical anti-icing method.

• Industrial feelers and composites

Epoxy resin has important applications in industrial production and is commonly used in the manufacture of production aids such as molds, master models, laminates, castings and fixtures. Compared with traditional materials such as metal and wood, epoxy resin molds not only improve productivity, but also reduce costs and shorten production cycles. It is also widely used in the production of reinforced fibers and composite parts. Although epoxy resins are more expensive than polyester and vinyl ester resins, the composite parts they produce typically have higher strength and heat resistance.

• Coating Applications

Two-component epoxy coatings can be used on metal substrates in heavy industry, and such coatings offer higher hardness and durability than conventional heat-cured powder coatings. Fusion bonded epoxy powder coatings are widely used for corrosion protection of steel pipes and fittings as well as concrete reinforcing bars in the oil, gas and potable water industries. Epoxy coatings are more heat resistant compared to latex and alkyd paints and are widely used in industrial and automotive applications. It can also be used as a primer to improve the adhesion of automotive and marine coatings, and is particularly suitable for rust and corrosion protection on metal surfaces where high corrosion protection is required. Metal cans and containers are often coated with epoxy resin coatings, especially for preventing metal corrosion caused by acidic foodstuffs such as tomatoes. In addition, epoxy resins are used for decorative flooring, such as terrazzo, crushed stone and colored aggregate floors, providing a decorative effect that combines aesthetics with durability.

• Manufacture of ships

There are two main uses for epoxy resins in the marine sector. One is that epoxy resins are used in the manufacture of components that require high strength or weight ratios because they have better mechanical properties than the more common polyester resins. The second is that epoxy's high strength, good gap-filling ability, and excellent adhesion to a variety of materials, including wood, make it one of the most important materials used in the construction of ships.

Epoxy resins are also commonly used in ship repair, where they are used to repair and assemble ships, followed by a coat of paint with UV protection for added protection.

• Petroleum and petrochemical

Epoxy resins also play an important role in the petroleum sector. It is used to treat selective layers that generate excess brine in plugged reservoirs, thereby reducing well blow-outs and increasing crude oil production, a technique known as “plugging treatment”.

• Realm of art

Epoxy resins mixed with pigments can be used as a painting medium to form a complete picture by layering them on top of each other. Epoxy resins are also used for decorating artwork and furniture. With a seamless, glossy finish that can be molded into a variety of shapes, epoxy is the material of choice for creating minimalist pieces in modern furniture design.

In the future, we will continue to dedicate ourselves to innovative research in building structural reinforcement and maintenance, and constantly improve the quality of our materials. Each project is a continuation of our commitment and the practice of industry standards. We are confident that through hard work and innovation, structural reinforcement will usher in a more reliable and lasting tomorrow. Thank you for reading, sharing and paying attention!

Epoxy resins play a vital role in the electronics industry due to their excellent physical and mechanical properties, electrical insulation, and adhesion to various materials. Especially in the field of electronic packaging, the use of epoxy resin not only ensures the stable realization of chip function, but also greatly affects the quality of semiconductor devices. In such a background, the red phosphorus paste RP-EP of red phosphorus coated epoxy resin developed by YINSU Flame Retardant Company is particularly suitable for electronic epoxy plastic sealing material with its characteristics such as high viscosity and stability. The development of this material not only meets the electronics industry's demand for high-performance encapsulants, but also opens up new possibilities for the application of epoxy resins, signaling that structural reinforcement and electronic encapsulant materials will move towards a more reliable and durable future.