Epoxy resin has many industrial applications and possesses greater thermal and chemical resistance – as well as strengthened mechanical properties – than other types of resin. When in liquid form, epoxy resin is poured into a mold or painted over a material in layers to create a protective outer coating. After curing, the material hardens into a solid and becomes durable and structurally stable. This combination of features makes epoxy resin extremely useful in a number of applications, from industrial tooling to art projects and automotive manufacturing

The specific combination of chemical compounds and polymerization processes will impact the resulting core characteristics of an epoxy resin formula.

Here are some of the trademark properties of epoxy resin formulas:

  • Heat-resistance
  • Chemical stability
  • Electrical insulation
  • Low moisture absorption
  • Durable adhesive bond
  • Anti-corrosive
  • Excellent fatigue strength and flexural strength
  • Low shrinkage after curing
  • Absence of VOCs (volatile organic compounds)

To begin the application process the epoxy resin is mixed with a co-reactant, also called a hardener, which typically comes in a separate compartment of the same package. The chemical reaction begins as soon as the two chemicals are mixed and depending on the formulation can become solid very quickly or slowly depending on your requirements.  The epoxy resin manufacturer should provide instructions about the ratio of epoxy to hardener that should be used to achieve maximum strength and performance.

What’s the Difference Between Casting and Coating Epoxy Resins?

Casting and coating epoxy resins are unique but related compounds. Choosing between the two will ultimately determine how the finished product will look and function.

Casting resins, also called “deep-pour resin” or “pouring plastic,” are used for clear encasings and suspensions. The user pours the material into a mold and then cures it to retain the same shape. Casting resins are commonly used to create crafts, jewelry, sculptures, and memorabilia. Manufacturers can also produce aggregate, molded plastics, or electrical insulation with casting resin. Engineers design automotive parts, aerospace devices, sports equipment, and hundreds of other products with compounds that are fortified with epoxy resin.

Coating resins, on the other hand, are aptly named: they are used to coat materials, such as metal, concrete, or wood, to make them stronger, chip-resistant, easier to clean, water-resistant, and rust-proof. A thin layer of coating resin can also glue materials together or preserve paper. In the electrical manufacturing sector, coating resins are applied to overmold circuits and transistors, which holds components together and protects against corrosion.

Beyond these differences in application, there are a few other notable distinctions between casting and coating epoxy resin:

  • Viscosity: Casting resins are normally thinner compared to coating resin.
  • Curing Times: Because liquid casting resin is poured into thick layers, they take longer to cure to avoid shrinkage and heat build up..
  • Hardness: Coating resins are usually stiffer and harder than casting resins.
  • Mix Ratio: Most coating resins use a 1:1 ratio, but casting resin formulas can vary, such as 1:1 or 2:1.

Even though there are significant similarities between the two formula types, it’s usually easier to use the formula that’s best suited to your intended application.

If you pour casting resin on a surface instead of using a thin layer of coating resin, for example, the resin will run off the edges and will be very slow to harden.

Alternatively, if you pour coating epoxy into a mold, you’ll need to pour multiple thin layers and wait for the material to cure between applications. Otherwise, the heat generated from the material poured in a large mass will accelerate the chemical reaction and cause yellowing or cracking.

Key Questions to Consider About Epoxy Resin

If you are not sure what type of epoxy resin to opt for, consider the following:

  • How thick is the layer of epoxy you need for this project?
  • How long can you wait for the epoxy to cure?
  • Do you need a mold or frame to prevent dripping and hold the epoxy while it cures?
  • How hard does this material need to be to withstand the expected wear?
  • Do you want to suspend materials in the epoxy resin?
  • Do you need the epoxy to have any special properties?
  • Will this material be exposed to extreme temperatures, water, chemicals, UV rays, or other potentially damaging elements?

Epoxy resin systems can be tailor-made to suit unique project needs. Manufacturers use a variety of co-reactants, including, for example, polyfunctional amines, phenols, and alcohols all of which produce slightly different results. The type of base epoxy and additives in the formula can also change the resin’s viscosity and intrinsic properties.

Epoxy Resin Viscosity

Viscosity describes a liquid’s degree of resistance to flow. Within the context of epoxy resin formulas, the viscosity determines if the material will drip or spread evenly and if it should be poured, dipped, or painted on the material. Viscosity also affects how much of the epoxy perforates the substrate and which physical properties are produced.

For example, at Copps Industries, we manufacture three lines of epoxy resin with low, medium, or high viscosities:

  1. Low Viscosity

Low-viscosity epoxy resin is thin and works well for deep-level penetration and filling small cavities. The consistency helps prevent air bubbles, which facilitates bonding between the epoxy and substrate. You can use low-viscosity epoxy resin for encapsulation, sealing, and potting.

  1. Medium Viscosity

Medium-viscosity epoxy is thick. It’s less permeable than low-viscosity formulas and offers greater mechanical strength. The material can withstand moderately high temperatures and is often used for filament winding, vacuum bagging, and tooling.

  1. High Viscosity Epoxy

High-viscosity epoxy has a paste-like consistency and is the most resilient option. It offers superior adhesion and shock- and heat-resistance. Technicians use this formula for projects that demand exceptional durability and strength.

Epoxy Resin Solutions at Copps Industries

Copps Industries has been a leading provider of quality epoxy resin solutions for over four decades. Our formulations are thoroughly tested for quality assurance and have demonstrated practical applications in a broad range of industries. To learn more about epoxy resins or about our products and capabilities, reach out to us or request a quote today.


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