Epoxy resins, especially bisphenol A-based types, have evolved from simple DIY craft projects to essential materials in high-demand industrial applications. Known for their exceptional adhesion, chemical resistance, and versatility, epoxy resins are widely used in coatings, adhesives, electronics, and construction. Whether you’re a hobbyist creating custom artwork or a manufacturer developing protective coatings for large-scale infrastructure, epoxy resins provide adaptable solutions for both creative and technical needs.
In this article, we will explore the wide range of applications, properties, and challenges that make epoxy resins a cornerstone in both DIY and industrial environments.
What is Epoxy Resins?
Epoxy resin refers to a group of high molecular compounds containing two or more epoxy groups in their molecular chain structure. It belongs to the category of thermosetting resins, with the most representative resin being Bisphenol A-type epoxy resin.
Characteristics of Epoxy Resins (Typically Bisphenol A-type Epoxy Resins)
1, Epoxy resin alone has little practical value; it needs to be used with a curing agent to become functional.
2, High adhesive strength: Epoxy resin adhesives rank among the top in synthetic adhesives for bonding strength.
3, Low shrinkage upon curing: Among adhesives, epoxy resin has the lowest shrinkage rate, which contributes to its high bonding strength.
- Phenolic resin adhesive: 8–10%
- Silicone resin adhesive: 6–8%
- Polyester resin adhesive: 4–8%
- Epoxy resin adhesive: 1–3%. Modified epoxy resin adhesives can have a shrinkage rate as low as 0.1–0.3%, with a thermal expansion coefficient of 6.0×10⁻⁵/°C.
4, Good chemical resistance: The ether groups, benzene rings, and aliphatic hydroxyl groups in the cured system are resistant to acid and alkali corrosion. It can be used for two years in seawater, petroleum, kerosene, 10% H₂SO₄, 10% HCl, 10% HAc, 10% NH₃, 10% H₃PO₄, and 30% Na₂CO₃. It can also withstand soaking in 50% H₂SO₄ and 10% HNO₃ for half a year at room temperature, and 10% NaOH (100°C) for a month, with performance remaining stable.
5, Excellent electrical insulation: The breakdown voltage of epoxy resin can exceed 35 kV/mm.
6, Good processing performance, dimensional stability, resistance properties, and low water absorption. While Bisphenol A-type epoxy resin has many advantages, it also has some drawbacks:
- High operating viscosity, making application slightly inconvenient.
- The cured material is brittle with low elongation.
- Low peel strength.
- Poor resistance to mechanical and thermal shock.
Applications and Development of Epoxy Resins
Development history
Epoxy resin was patented by P. Castam in 1938. The Swiss company Ciba developed the first epoxy adhesive in 1946, and in 1949, S.O. Creentee in the U.S. developed epoxy coatings. Industrial production of epoxy resin began in China in 1958.
Applications
- Coating industry: Epoxy resin is widely used in coatings, especially water-based coatings, powder coatings, and high-solid coatings. It is commonly used in industries such as pipeline containers, automobiles, ships, aerospace, electronics, toys, and handicrafts.
- Electronics and electrical industries: Epoxy resin adhesives are used in electrical insulation materials, such as the sealing and potting of rectifiers and transformers, the sealing and protection of electronic components, insulation and bonding of electromechanical products, sealing and bonding of batteries, and surface coating of capacitors, resistors, and inductors.
- Hardware accessories, handicrafts, and sports goods industries: It is used in nameplates, accessories, trademarks, hardware, rackets, fishing gear, sports goods, handicrafts, and other products.
- Optoelectronics industry: It is used in the encapsulation, potting, and bonding of LED lights, digital tubes, pixel tubes, electronic displays, and LED lamps.
- Construction industry: Widely used in roads, bridges, floors, steel structures, buildings, wall coatings, dams, construction projects, and cultural relic restoration.
- Adhesives, sealants, and composites: It is used for bonding wind turbine blades, handicrafts, ceramics, and glass, as well as composite carbon fiber boards and microelectronic material sealing.
Epoxy Resin Adhesive Characteristics
Epoxy resin adhesive is a modified or further processed version of epoxy resin, designed to meet specific performance requirements. It also needs to be used with a curing agent, and it requires thorough mixing to fully cure. Generally, the epoxy resin adhesive is referred to as “A” glue or the main agent, while the curing agent is called “B” glue or hardener.
Characteristics before curing
- Viscosity: Refers to the internal friction resistance generated by the colloid when it flows. Its value depends on factors like material type, temperature, and concentration.
- Gel time: The time it takes for the adhesive to transition from a liquid to a semi-solid state during curing. Gel time is determined by factors such as the amount of mixed epoxy, temperature, etc.
- Thixotropy: The property of a material to become less viscous when subjected to external forces (shaking, stirring, vibrating, etc.), and return to its original viscosity once the external force is removed.
- Hardness: The resistance of the material to indentation or scratching. Common measurement methods include Shore, Brinell, Rockwell, Mohs, Barcol, and Vickers hardness. Among these, the Shore hardness tester is simple and widely used in production testing.
- urface tension: The force exerted on the surface molecules of a liquid, pulling them inward and reducing the surface area, measured in N/m. Surface tension depends on the nature, purity, and temperature of the liquid.
Main characteristics after curing
- Resistivity: Describes the material’s electrical resistance, usually measured as surface or volume resistance. Surface resistance is the resistance measured between two electrodes on the same surface, while volume resistivity refers to the resistance across the thickness of the material.
- Voltage resistance: Also known as dielectric strength, it is the voltage required to cause electrical breakdown in a material.
- Water absorption: Measures the degree to which a material absorbs water.
- Tensile strength: The maximum tensile stress that a material can withstand before breaking, measured in MPa.
- Shear strength: The maximum load a bonded surface can bear before shearing, also measured in MPa.
- Peel strength: The force required to peel a bonded surface, measured in kN/m.
- Elongation: The percentage increase in length of the material under tensile stress.
- Heat deflection temperature: The temperature at which the material deforms under a specified load.
SIOResin® Epoxy Resins
SIO-2130H Epoxy-Modified Silicone Resin
Our SiO-2130H is an epoxy-modified silicone resin that offers outstanding resistance to both high and low temperatures, along with excellent hydrophobic and moisture-resistant properties. Its superior electrical insulation and arc corona resistance make it an ideal choice for demanding applications. Additionally, this resin provides exceptional weatherability, chemical stability, and corrosion resistance.
Widely used as a high-temperature anti-corrosion coating (≥500°C), SiO-2130H cures fully at room temperature as part of a two-component system, with enhanced performance when baked. It is also well-suited for use as an H-class insulation coating, making it versatile for various industrial applications.
About SIOResin (SIO New Material)
SIOResin is a leading company in China specializing in the development and production of new materials. We manufacture and supply high-quality water-based silicone resins, silicone-modified polyesters, water-based polyurethanes, water-based acrylics, UV resins, liquid silicone rubber, intumescent fireproof coatings, flame retardants, wetting agents, curing agents, associative thickeners, driers, soft-touch agents, and other additives. Our products have a wide range of applications and with competitive prices.
Free samples are available upon request. Please feel free to contact us at any time.
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