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Fire Retardant Epoxy: Combining Safety With Performance

Click to ExpandFire Retardant Epoxy

Fire retardant epoxies are epoxy resin systems formulated to minimize the flammability of materials, and thus reduce the longevity and spread of fire. They incorporate various additives or fillers that effectively hinder or delay combustion when subjected to heat or flames. These specialized components find widespread application in industries where fire safety is paramount, including aerospace, construction, electronics, and automotive.

Fire resistance is increasingly becoming an important requirement in specifying adhesive systems. Across a wide range of applications, a fire retardant adhesive system can offer a safer use of many devices and systems. Incidents associated with fire outbreaks, resulting in significant damage and personal injury, have focused attention on how materials perform in combating the effects of fire. A number of approaches mitigate the destruction when a fire breaks out, and a fire retardant epoxy resin system may play an important role in this effort.

In this Blog, we will examine the composition and functionality of a fire retardant epoxy. We will also look into its various applications across different industries.

Essential Components of Fire Retardant Epoxies

Various components must be carefully balanced to create epoxies that offer enhanced fire safety without compromising performance. Here are the essential elements:

Epoxy Resin

Epoxy resins are typically formed by reacting epichlorohydrin with bisphenol-A or related chemical compounds. They offer excellent adhesion to various substrates or surfaces, superior mechanical properties, including tensile strength, durability and longevity, chemical and corrosion resistance, electrical insulation and other remarkable electrical properties, thermal resistance, dimensional stability, adaptability to achieve specific performance qualities, aesthetic qualities, and ease of application. They also serve as the matrix for the flame retardant additives and fillers, ensuring structural integrity, along with these other qualities, in the composite material.

Flame Retardant Additives

Fire is the result of heat, fuel, and oxygen. Combustion occurs when a certain ratio is established between the oxygen and heat, thus igniting the polymer. The objective of a flame retardant is to remove one of the processes contributing to the combustion cycle. Flame retardant additives work by disrupting the combustion process through different mechanisms. For example, halogenated compounds release halogen radicals during combustion, which interferes with the chain reaction or the reactions in a flame. Halogenated (chlorinated and brominated) compounds can interrupt the combustion process to slow down a fire and thus are effective fire retardants. In the halogenated compounds, the brominated compound fire retardants have been the most effective.  Phosphorus-based flame retardants form a protective char layer when exposed to heat, insulating the material, removing the carbon fuel source, and preventing further combustion. Phosphorus-containing compounds have been identified as promising flame retardants, as they are efficient charring agents and exert flame retardant in both gaseous and condensed phases. Other alternative fire retardant compounds include nitrogen-based compounds, alumina trihydrate (ATH) and magnesium hydroxide fillers, intumescent flame retardants, and zinc borate. In general, there are flame retardant additives that interfere with the combustion process and offer formulating options. Selecting a flame retardant for an epoxy resin system has many ramifications, as the materials must not interfere with final product performance. Care must be taken in selecting the right flame retardant system for a specific application.


Inorganic materials such as alumina trihydrate (ATH) and magnesium hydroxide are often incorporated into fire retardant epoxies to enhance their mechanical properties. When exposed to fire, these fillers absorb heat and release water vapor, thus cooling the material or volatile fuel, and extinguishing flames. They can also dilute the epoxy matrix, or interfere with the chain reactions in the flame, which reduces its overall flammability and improves its fire resistance.

Hardeners and Catalysts

Hardeners and catalysts initiate and accelerate the curing process. Typically, epoxy resins require the addition of a hardener or curing agent to cross-link the polymer chains and form a solid, three-dimensional network. This cross-linking reaction is essential for achieving the epoxy’s desired mechanical properties, stability, work life, and other qualities. Epoxy resin systems formulated by incorporating latent curing agents, to create one-part epoxy systems, offer benefits such as simple operations, stable product quality, and convenience for industrial production.

Stabilizers and Modifiers

Stabilizers and modifiers may be included in fire retardant epoxies to enhance performance of the flame quencher, achieve specific properties, or improve processing conditions. Stabilizers help prevent epoxy resin degradation due to exposure to heat, UV radiation, or other external factors. Meanwhile, modifiers can alter the epoxy’s adhesion to substrates, viscosity, flexibility, toughness, or other properties to better suit the intended application.

Applications of Fire Retardant Epoxies

Below are various industries that leverage the unique properties of a fire retardant epoxy:


Fire retardant epoxy systems play a crucial role in enhancing safety and durability in the aerospace industry. The aerospace industry uses fire retardant epoxies to create aircraft components, including interior panels and interior cabin components, seat structures, and cargo compartments. They are used also in composite structures, for electrical potting and encapsulation, for thermal insulation, as adhesives and sealants, and as protective coatings. These epoxies are beneficial in the construction of drones and drone components. They help meet stringent safety regulations in the aerospace industry by enhancing fire resistance while maintaining structural integrity. As a result, aircraft are safer and more efficient.


In the construction sector, fire retardant epoxies are critical components in building safety and integrity, by enhancing fire resistance and containment. They find application in building materials such as fire doors, wall panels, and structural reinforcements. They are integral to fire-stop systems designed to prevent the spread of smoke and fire between building compartments. They help improve the fire resistance of structures, reducing the spread of flames and minimizing the risk of fire-related damage or collapse. The use of fire retardant systems in construction is guided by building codes and standards, designed to improve fire safety and thereby protect lives and property.


Sensitive electronic components require protection from fire hazards. Fire retardant epoxy systems are widely used to encapsulate and pot electronic components, to safeguard these parts and help ensure reliable performance in high-temperature or other rough environments. Fire retardant epoxy systems may significantly reduce the risk of potential short circuits or overheating within the electronic device. These important systems are used for printed circuit board (PCB) coatings, for electrical and cable insulation, as underfill materials for circuit boards, for LED encapsulation, and in the manufacture of connectors and housing. These systems are designed to meet regulatory standards and requirements, such as the Underwriter Laboratory (UL Solutions) 94 standards for flammability.


Fire retardant epoxies play a vital role in various modes of transportation, including automotive, rail or trains, and marine and ships. They are used in vehicle interior parts such as dashboards and door panels, battery housings for electric vehicles (EVs), engine compartments, in electronic parts such as sensors, and structural components, to enhance fire safety and meet regulatory requirements for passenger safety.

In the rail industry, there are similar uses in interior panels, seating, flooring, electrical insulation and electronic potting and encapsulation. Flame retardant epoxy systems are used importantly in the marine industry for construction and repair of ships, in particular in engine rooms and electrical control rooms. As noted above, flame retardant epoxy systems are crucial for safety of aircraft components. Similar uses are applied in the manufacture of public transport vehicles and recreational and other specialty vehicles. All are designed to meet regulatory safety standards to enhance safety and save lives and mitigate property damage.

Military and Defense

Military applications often require materials with superior fire resistance and durability, to enhance the safety and performance of equipment, vehicles and structures. Given the crucial importance of combat operations and the challenging, hazardous, high-risk environments of military and defense operations, stringent safety requirements are a necessity. The importance of flame retardant epoxy systems as discussed in all the applications and industries noted above generally are fully applicable to the military and defense industry. Critical uses are found in vehicle protection, aerospace applications, electronic and electrical systems, weapons and munition systems manufacturing and storage, protective gear manufacturing, sealings and protective coatings, fire-stop systems and in composite materials made with flame retardant materials. These materials are used in a wide variety of applications, including drone airframes, to enhance safety and performance.

Fire retardant epoxies are used in military vehicles, aircraft, drones and naval vessels to enhance survivability and protect personnel and equipment from fire-related threats.

Industrial Manufacturing

Various industrial processes involve handling flammable materials or operating in environments where fire hazards are prevalent. Fire retardant epoxies are employed in equipment enclosures, machinery parts, and manufacturing facilities to reduce the risk of fire accidents. Their application includes many of the purposes discussed above to enhance fire safety and durability. These include uses as protective coatings, in electrical insulation and electrical potting and encapsulation, in structural and composite materials, as fire barrier or fire-stop systems, in cable and wire coatings, in storage containers, and in maintenance and repair. As with all the applications discussed above, these fire retardant materials create a safer environment to protect lives and property.

Choose United Resin for High-Quality Epoxy Solutions Where Fire Safety is a Priority

United Resin offers an extended portfolio of epoxy systems that exceed industry standards for safety and performance. Our portfolio includes a wide range of solutions designed to meet the stringent demands and requirements of various applications to enhance fire safety.

EL-CAST VFR PLUS, Underwriter Laboratory (UL Solutions) approved at 94 V-O, is United Resin’s newest innovation where fire safety is a priority. It is a filled, low viscosity, high temperature potting and encapsulating resin, with superior flame resistance, achieves 0 second AfterFlame with certain hardeners, has no flame drip and is easier to mix. The resin has excellent bonding properties, a high gloss finish with minimal shrinkage and with 117 hardener is a soft 94 V-O material. It is ideal for transformers, alarm systems, filters, magnetic components and surge protectors. Similar systems also are available with different hardeners.

United Resin provides tailored consulting services to assist clients in selecting the best epoxy system for their needs. Where fire safety is a priority, contact us.

The information presented in this Blog is intended for general background and informational purposes only and is not intended 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.

Contact us today or request a quote to get started!

How To Select the Right Structural Adhesives

In many industries, adhesives play a crucial role in bonding materials together. Structural adhesives are particularly well-suited for assembling and joining components that require exceptional strength and durability. Structural adhesives are an important element in the structural integrity of load-bearing and stressed assemblies during their forecast service lives. They are also often used to replace traditional fastening methods — such as welding or riveting — as they improve aesthetics and reduce weight. Epoxy adhesives can bond a wide range of materials.

Click to ExpandHow-To-Select-the-Right-Structural-Adhesives

Given the diverse range of formulations in the market, selecting the appropriate adhesive for a specific application can be challenging. This article will cover the key factors to consider when choosing the right type for your needs.

Key Considerations When Selecting the Best Structural Adhesives for Your Project

A systematic approach to identifying your requirements is crucial for finding the appropriate structural adhesive. The following are several factors you should consider:

Bonding Process

Defining your precise needs for bonding agents requires careful consideration of the type of bonding process required. For instance, depending on the specific requirements of your application, you may need to use multiple bonding processes and structures. Adhesive application methods include manual application, spray application, and automated dispensing.

Manual application entails using a brush, roller, or syringe to apply adhesive by hand. Spray application involves using a spray gun or similar device to spray the product onto the substrate. Finally, automated dispensing employs a machine or robot to apply the product with precision and consistency, ensuring a reliable and repeatable bond. The application method can affect the adhesive’s performance and effectiveness under the particular design requirements.

Bond Strength

Bond strength measures the adhesive’s ability to hold two or more surfaces being bonded together under mechanical stress or load. A strong and long-lasting bond typically requires epoxy adhesives due to their high strength and durability. This makes epoxy resins suitable for bonding materials subject to high loads or stresses. Structural adhesives can improve product performance by distributing loads more evenly, thus better addressing stress concentrations and fatigue resistance.

Material Compatibility

Modern structural adhesives offer a vast array of options. Using purpose-made adhesives specifically designed for bonding particular materials is strongly recommended. This is because different products have varying chemical compositions and bonding mechanisms that work best with specific materials. The adhesive must be compatible with the particular substrate.

For example, some adhesives may be more suitable for bonding metals, while others may work better with plastics. Additionally, adhesives designed for composites often have specific formulations optimized for the unique challenges of bonding these materials. These challenges may include their low surface energy and sensitivity to moisture. Overall, structural adhesives can offer design flexibility since they can bond together a wide range of materials, but some adhesives are better suited for particular joint designs.

Curing Time

The curing time is the amount of time it takes for the adhesive to fully harden and develop its maximum strength. It can vary widely depending on the adhesive type, the bonded materials, and the environmental conditions. Selecting an adhesive that cures quickly can save time and increase efficiency, while a longer curing time can offer a stronger and more durable bond. A longer curing time allows for adjustments to be made before the adhesive sets or cures. The curing time needs to be appropriate for the production time requirements and the particular application’s requirements.

Temperature Resistance

Structural adhesives can maintain their bond strength only within certain temperature ranges that vary between different types of adhesives. Therefore, comparing the temperature parameters of various adhesives is crucial. This will ensure you select a product that can withstand your application’s heating or cooling conditions or cycles.

A Better Finished Appearance and Resistance to Many Harsh Environmental Conditions

Structural adhesives can offer improved aesthetics, as they can bond materials with no visible fasteners. They produce a better finished appearance to an application. Since epoxy resins can fill gaps between materials, they are often used in applications where a perfect fit is not possible. Epoxy resins also are resistant to a wide range of chemicals, making them suitable for harsh environments. Epoxy resins can eliminate potential corrosion issues at the bond line, and can withstand many environmental conditions that the bonded materials will experience in their life cycle.


An adhesive should be chosen without compromising quality, as a cheaper product may eventually cost more if it fails to perform. It is worth considering the long-term benefits of investing in a high-quality adhesive, such as increased durability and enhanced bond strength. This can lead to cost savings on future maintenance and repairs. Reduced maintenance, improved durability and increased performance make epoxy resin a cost-effective solution to your adhesive needs. The cost of a high-quality adhesive should always be considered in relation to the total cost of the finished product or application.

Choose United Resin for Exceptional Adhesive Solutions

For over 50 years, United Resin has been delivering high-quality epoxy resin systems offering adhesive solutions for various industries. United Resin has a variety of specialty and structural adhesive systems that meet the requirements of the aerospace, marine, automotive, construction and many other industries. Our portfolio of structural adhesive systems includes:

Metal Paste with 215 Hardener, a thixotropic structural adhesive which cures at room temperature and possesses superior strength up to 350F/177C. It is ideal for filling gaps and bonding materials as this system develops adhesive strength quickly.

High-Temp Adhesive with 210 Hardener, a two-component, low viscosity, room temperature cure system with excellent strength at 300F/149C. It may be used for repair applications, including laminating, injection, and coating.

Flex A Bond with 740, available in our regular formulation, a sprayable formulation and a paste formulation. A key advantage of this epoxy structural adhesive is its ability to bond hard to bond materials such as PTFE, nylon, ceramics and stainless steel. This system also works well as a vibration dampening adhesive material. As with all epoxies the Flex A Bond with 740 has very good chemical resistance.

Hi-Strength Tuff Bond with 250 Hardener, a non-sagging thixotropic room temperature cure, high strength adhesive for a variety of substrates, including those hard to bond materials such as PTFE, nylon, acetal, and stainless steel. Hi-Strength Tuff Bond with 250 Hardener is a toughened industrial grade adhesive that has superior thermal shock resistance, chemical resistance, vibration dampening and impact resistance.

Our manufacturing processes are designed for consistent quality and performance. We also have global shipping capabilities, ensuring we can reach you regardless of location.

Contact us today to explore our high-quality epoxy resin systems, including structural adhesive solutions. You can also request a quote to see how we can help meet your needs.

How To Maintain Dielectric Strength

Dielectric strength measures the electrical insulation properties of a material or substance, which is important in electrical engineering, power generation, telecommunications, and other industries. Maintaining the dielectric strength of a material is vital to ensure the safety and reliability of equipment and systems. In dielectric breakdown, the material’s resistance decreases rapidly and becomes electrically conductive (short circuits). The measure of dielectric strength is expressed as Volts per unit thickness (V/mil). ASTM International (American Society for Testing and Materials) publishes several standard tests for determining dielectric strength in certain applications.

Epoxy resins are a key material in applications requiring outstanding electrical insulation properties. Epoxy resins are widely used as insulating materials in electrical specifications because of their excellent thermal stability and dielectric properties. Moreover, epoxy resins offer excellent adhesion to various materials (substrates), toughness, durability, and superb chemical and heat resistance. As a result, epoxy resins are used extensively in potting and encapsulation applications. Overall, epoxy is an excellent insulating material due to its high dielectric strength, which makes it a preferred choice for electrical and electronic applications where high voltage levels are involved.

These are the key steps in maintaining dielectric strength to prevent potential failures:

1. Keep the Material Clean

Maintaining dielectric strength begins with keeping the material or substance clean and free of impurities. Dust, dirt, grease, oil, salts, and other conductive substances can reduce a material’s dielectric strength, resulting in probable failures and equipment damage.

2. Avoid Extreme Temperatures

Another crucial aspect of preserving dielectric strength is to prevent the overheating of the material or substance. High temperatures can deteriorate a material, resulting in a loss in dielectric strength. Therefore, it is critical to continuously monitor the temperature of equipment and systems and take appropriate measures to keep them cool.

3. Regularly Test the Dielectric Strength

It is important to regularly test the dielectric strength of a material or substance to verify that it remains within acceptable parameters. It may be accomplished using various techniques, including high-potential and dielectric loss testing. Dielectric strength should be tested and validated by users in specific applications, as the dielectric properties will vary based on the operating conditions of the application.

  • High-potential testing:

    This test determines a material’s dielectric strength and identifies any weaknesses or defects in the insulation. It involves applying a high voltage to a material for a short period and observing if an electrical breakdown occurs. The voltage used is usually higher than the maximum operating voltage the material will be exposed to in service.

  • Dielectric loss testing:

    This test measures the energy absorbed by a material when an AC voltage is applied. It provides information about the quality of the insulation and its ability to resist electrical degradation over time. Thus, the results of dielectric loss testing can be used to predict a material’s long-term reliability and identify areas that may require improvement.

By appropriate testing, potential issues can be recognized early and corrected before they cause equipment failure.

4. Ensure Proper Storage

Another key element to consider in preserving dielectric strength is proper storage. The item or substance should be kept in a regulated environment to avoid damage or contamination. For example, it might involve keeping the material dry and within the appropriate temperature range. Proper storage can also help to increase the material’s lifespan and prevent any breakdowns or malfunctions.

5. Maintenance and Inspection

Keeping a material’s dielectric strength requires proper maintenance and inspection of the equipment and systems in which the material is used or contained. Regularly examining equipment can aid in the early detection of possible problems and prevent equipment failure. Check for wear and tear, monitor for signs of degradation, and replace parts as needed.

Dielectric Strength: Built To Last With United Resin

At United Resin, we specialize in providing high-quality epoxy resin systems and have a wide range of epoxy resin systems with superior electrical insulation qualities and superior dielectric strength! Our systems offer many benefits, including thermal conductivity, high-temperature resistance, optical qualities, high strength, vibration dampening, and flame retardance. They are used in various electronics, medical, and construction industries.

With over 50 years of experience and high-quality customer service, our team of experts is dedicated to providing the best solutions to meet your needs. Our top priority is helping you select the appropriate product with the dielectric properties required for your equipment’s safety, quality, functionality, and reliability.

Contact us now to learn more about our dielectric epoxy resin systems and other services we can provide to benefit your business!

What To Look For in an Epoxy Putty Stick

Epoxy putty sticks are highly versatile and powerful adhesives utilized for various domestic, commercial, and military repairs. These epoxy doughs are made of two parts — resin and hardener — and can be quickly blended by hand-kneading. Furthermore, the putty is moldable to any form and can be applied to virtually any surface, even underwater.

Click to ExpandWhat-To-Look-For-in-an-Epoxy-Putty-Stick

This article will explain how a putty stick works and what factors to consider when choosing the right product for your application.

What Is an Epoxy Putty Stick and How Does It Work?

Also called epoxy repair sticks or adhesive metal, an epoxy putty stick is a two-part adhesive that involves kneading the resin and hardener together. This process activates a chemical reaction that starts the curing phase. Then, the mixture is applied to the surface to be repaired or joined, where it will harden into a strong, long-lasting bond over time.

Once cured, the hardened putty can be sanded, filed, painted, or stained to match the surrounding surface.

Key Considerations in Putty Stick Selection

When purchasing a putty stick, it is critical to consider key factors to ensure that you select the product that will meet your needs. The following are some of the most crucial factors to consider in product selection:

Curing Time

Curing time refers to the duration it takes for the putty to harden and reach its maximum strength. Most putty sticks require some time to cure, with the exact length depending on factors like temperature, humidity, and the specific product being used. On the other hand, some putties can cure in as little as a few minutes.

It is critical to adhere to the manufacturer’s instructions for curing time and other product-specific guidelines. Attempting to sand, file, or manipulate the putty before it has fully cured can lead to a weaker bond or other problems.


The specific product and the material’s composition determine the putty’s strength. When assessing this factor, it is critical to consider the type of repair being performed and the stress that will be placed on the repaired area. For example, some putty sticks are intended for heavy-duty applications, such as automotive or marine repairs. Meanwhile, others may be better suited for smaller, less demanding maintenance.

Ease of Use

Epoxy putty sticks are designed to be simple and require little preparation. One of its advantages is that it can be easily shaped or sized by hand, making it an excellent choice for quick repairs. The two-part putty is also simple to mix and apply, as no special tools or equipment are required.

Look for a product that is easy to prepare and use, and consider the pliability of the putty when kneading it together. A putty that crumbles or is difficult to work with can make a repair project more frustrating and time-consuming than it needs to be.

Shelf Life and Storage Requirements

Putty sticks typically have a long shelf life, often lasting several years if stored properly. However, looking for products with clear expiration dates and general guidelines is important. These include keeping the putty sticks in a cool, dry place and storing them away from direct sunlight or heat sources. Using expired or old products can result in a weaker bond or a failure to cure properly.

Epoxy Putty Sticks From United Resin

For over 30 years, United Resin has been manufacturing epoxy putty sticks and other related products. We currently offer Fastweld and Fastwood Epoxy Putty Sticks. United Resin’s sticks offer exceptional ease of use, in that the dough is pliable for mixing without crumbling. The results also are exceptional, in that the cured product is hard as steel.

Our Fastweld products cure in 5 and 20 minutes and harden like steel in 30 to 40 minutes. It forms a tenacious bond, even underwater. They also perform well at continuous temperatures up to 250 ℉ (121 ℃) and intermittent temperatures up to 450 ℉ (242 ℃). It adheres to aluminum, iron, steel, wood, glass, masonry, ceramics, and many plastics. It may be drilled, filed, tapped, or sanded after 1 hour of cure time. They come in three standard colors: black, gray and white.

The Fastwood sticks are cylindrical epoxy dough kits that can be activated by hand-mixing the material. They cure in five minutes and are specially designed for permanent wood repairs, including filling nail holes, replacing and reshaping wood parts, and general restoration. It forms a tenacious bond in minutes. It also performs well at continuous temperatures of up to 250 ℉ (121 ℃) and is available in standard natural and dark wood colors.

Choose United Resin for Your Adhesive Needs!

United Resin’s Fastweld and Fastwood Epoxy Putty Sticks are made with proprietary processes, ensuring top-notch quality for your repair needs! You can choose from our standard 3.5-inch and 7-inch lengths or request custom sizes and colors with minimum order requirements. Rest assured that all our materials are non-hazardous, REACH/RoHS compliant, and solvent-free.

Contact us today to experience the United Resin difference! You can also request a quote now.