Archive: May 2023

Key Considerations in Choosing Epoxies

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Epoxies are two-part thermosetting polymers that consist of a resin and a hardener. Polymerization (curing) is initiated when the resin is mixed with a hardener (sometimes referred to as a catalyst). Epoxy resins form cross-links during this process, creating a three-dimensional polymer of great mechanical strength.

Epoxy resins are known for their excellent adhesion, chemical resistance, and mechanical properties. They are typically sold in kits that contain the two components in separate containers, although some formulations are one-component systems. When mixed, the resin and hardener react to form a rigid, durable material. As a result, they can be used as adhesives, coatings, and encapsulants in a wide range of applications.  Some epoxy systems are specifically designed for particular applications, so it is important at the outset to consider the requirements of the intended use and select an epoxy that suits that application.

Choosing the right epoxy for a project can be complex, as different epoxy systems have varying physical and chemical properties. Epoxy resin systems are highly versatile because a wide range of processing, cure, and property characteristics can be achieved. Epoxy systems can be modified to enhance specific properties.  For example, where fire safety is a factor, epoxy systems can incorporate fire retardant additives to enhance the fire resistance or fire retardance of the system.

Here are the key considerations you should keep in mind when selecting an epoxy:

1. Physical Properties

The following are some of the key physical properties to consider:


The core quality of epoxy is its exceptional strength and adhesive properties, with its ability to form bonds of great strength and durability.  It’s crucial, however, to consider the surface (substrate) to which the epoxy will be applied to ensure good adhesion. Epoxy is compatible with various materials, including metal, wood, concrete, and many plastics. Some items are unsuitable for bonding with epoxy resin.

Tensile Strength

Tensile strength measures the maximum tension a material can withstand before breaking and failing. Epoxies with high tensile strength are suitable for applications where the material will be subject to pressure or pulling forces. Higher tensile strength is important for applications subject to great stresses and strains and where structural integrity is critical.

Flexural Strength

Flexural strength is a critical mechanical property that measures the ability of the epoxy to resist bending, flexing, or twisting forces without breaking and failure. It’s crucial to consider flexural strength for applications where the material will be subject to warping or twisting, such as in construction, aerospace, automotive, and marine applications. High flexural strength generally indicates a material that can withstand greater bending and flexing stresses.

Compressive Strength

It is important to consider the compressive strength of epoxy, where the application must withstand heavy loads or pressure without cracks or failure. There are epoxies with high compressive strength to ensure the stability, safety, and durability of those applications where structural integrity is critical. A higher compressive strength generally indicates a material that can withstand greater compressive or crushing forces and is important to ensure the structural integrity of the final product.


Epoxies are available in soft or harder systems.  If an abrasion resistant system is required, choosing an epoxy with high hardness is recommended.

Impact Resistance

Selecting an epoxy with high-impact resistance is ideal for projects requiring encapsulants or composite materials. This property ensures that the material can withstand sudden impact or shock. A related consideration is vibration dampening, where vibration may create undesired noise or lead to breaking and failure.

Heat Resistance

Epoxies with high heat resistance can withstand exposure to high temperatures, making them suitable for extreme heat applications. An epoxy system must be selected to handle the temperature range to which the application will be exposed, including high and low temperatures.

Chemical Resistance

Epoxies with high chemical resistance can resist degradation and damage when exposed to harsh chemicals or solvents. An epoxy system must withstand the particular chemicals to which it will be exposed.

Electrical Properties

In addition to the other physical properties of epoxy, epoxy is widely used in the electronics industry for its excellent electrical properties. Epoxy has high dielectric strength, making it ideal for insulating electrical components. It has a low dielectric constant, a factor in determining the capacitance of electrical parts, a low dissipation factor, high volume resistivity, and high surface resistivity, which are important measures for effective electrical insulation.

It also has low thermal conductivity, making it an excellent thermal insulator. The significance of these properties to a particular application should be considered in evaluating and selecting a suitable epoxy system.

Water Resistance

Epoxies with high water resistance are ideal for marine coatings, flooring, and other applications where water contact or moisture is expected.


A viscosity appropriate for the specific application is important. Viscosity can impact ease and manner of use and application.


Epoxy can benefit a project by improving its aesthetics. If important to the project, an epoxy that meets your needs for both finish and color (even clarity) should be considered. Epoxy also can improve application aesthetics by eliminating the need for metal fasteners in some bonding applications.

2. Mixing Ratio and Curing Time

It is imperative to accurately measure and completely mix the resin and hardener in the prescribed ratio to achieve the desired performance characteristics. Proper curing is essential for achieving optimal properties and longevity of the cured material. Following the manufacturer’s recommendations on curing time and environmental conditions is crucial to ensure the best results. The curing time will impact the production time of the application. An epoxy system may have a long or very short curing time, and a system may be formulated to fine-tune the desired working time.  The curing time determines the length of time to work with the material before it starts to harden.

3. Application Method

The method of application may be selected to best suit your needs and can also affect the performance of the epoxy. Application methods can be semi-automated or manual. Some methods are more suitable for certain applications than others and the selection of the appropriate method depends on the requirements of the project, its size and scope, and the desired outcome.  The following are some common methods of application:

Brush, Roller, Cartridge Gun, Syringe, or Bottle

Brush, roller, cartridge gun, syringe or bottle application are simple and cost-effective methods of applying epoxy. They are suitable for small to medium-sized projects and can be used for coatings and adhesives.


This fast and efficient method of applying epoxy is suitable for large projects and can be used for coatings, adhesives, and encapsulants.

Pour or Injection

Epoxy resin systems may be poured, via semi-automated or manual methods. The injection is a specialized method of applying epoxy that involves injecting the material into a cavity. It is commonly used for concrete repair and can be used for encapsulants and adhesives.  Dispensing machines are frequently used in potting or encapsulation applications, as they accurately mix and dispense the material in a controlled manner.

4. Precautions

It is important to follow all manufacturer’s instructions for use and precautions. Reviewing the safety data sheet (SDS) and taking the necessary precautions — such as wearing appropriate protective equipment and working in a well-ventilated area — are important.

5. Cost

The cost of epoxies can vary widely depending on factors such as quality, quantity, and application method. Because epoxy offers durability, reliability, low maintenance, versatility and reduced waste, among other factors, it can be the most effective cost solution to your application needs. The price must be evaluated in the context of these factors, as well as the performance requirements of the project.

Trust United Resin for Your Epoxy Resin Needs

United Resin is your trusted partner for your epoxy resin needs. With our wide portfolio of established epoxy resin systems and our continual focus on innovations to serve our customers, we are committed to providing high-quality and reliable solutions for various industries. In addition, we understand that a project may be unique and require specific properties, so we also offer custom formulation services to meet your particular needs.

Contact us today to explore our high-quality epoxy resin systems, including structural adhesive solutions. You can also request a quote to get started!

The information presented in this blog is intended for general background and informational purposes only and not as advice pertaining to any product, application, or process. We encourage you to contact us for information concerning your specific needs and requirements and to discover how United Resin may assist you.