Why Use Flame Resistant Adhesives and Potting Compounds?

Tech Tip

Master Bond flame resistant epoxy and silicone compounds are formulated to increase escape time, prevent injuries, save lives and protect property from smoke, toxicity, flames in trains, planes, buses, electrical/electronic devices, appliances. Select Master Bond grades have been developed to meet customer application requirements and certified to satisfy governmental/national recognized fire safety standards. It is important to note that governmental flame resistant specifications differ from country to country. Utilization of these products has been successful in reducing safety hazards, minimizing the need for replacement parts and mitigating the risks posed by employing inappropriate adhesive systems. Catastrophic consequences that can result from flammability reinforce the emphasis placed by design engineers in selecting the most desirable compounds to avoid faulty devices/equipment.

Master Bond two component UL94V-0 epoxy systems are engineered for potting, encapsulation and casting. These user friendly compositions have a simple one to one mix ratio by weight, low viscosity, toughness, thermal shock resistance, outstanding dielectric properties. They contain non-halogenated fillers, feature low smoke emissions and are self extinguishing. Specimens measuring 120-130 mm in length, 12 mm-13.5 mm in width and 2.75-3.25 mm thick were vertically tested to satisfy stringent UL94V-0 specifications. Self extinguishing occurred within 10 seconds. Additionally to pass the vertical burn test cotton placed beneath the specimen will not ignite from the drips. These UL94V-0 potting polymeric resin formulas are globally recognized for use on switches, connectors, sensors to transformers, power supplies, PCB boards, control modules, capacitors, resistors. Free flowing antimony free systems fill small gaps, cavities, tight clearances to provide void free insulation to maximize effectiveness.

Flame Retardant Epoxies

Special flame retardant silicone compounds combine high flexibility and thermal stability. Single component products require no mixing, have relatively fast set-up times, are non-corrosive and adhere well to glass, metal, many plastic substrates. They exhibit high elongation, superior electrical insulation properties, pass UL flame classification for thicknesses of 0.75 mm (UL94V-1) and for 3 mm thickness (UL94V-0). In contrast Master Bond's moderate viscosity addition curing silicone passes UL94V-0 testing for flame retardancy. This two component product does not require exposure to air for complete cross-linking and can cure in thicknesses well beyond 1-2 inches. Formulas are 100% solids, have exceptional resistance to impact, shock and have low exotherm on cure. This select composition has excellent thermal conductivity and outstanding heat dissipative characteristics. This system has proven ideal for potting/encapsulation. (They have been instrumental in preventing five risks, especially in miniaturized electronic devices with accelerated processing power.)

Durable fire resistant epoxy systems pass vertical and horizontal burn tests per FAR, 4CFR 25.853(a) for bonding, sealing, coating, potting applications. Products EP90FR-H, EP90FR-V, EP90FR-HFL were tested per Amendment 25-116 and Part 25 Appendix F. They were developed for use in aircraft interiors such as cabin, and cargo compartments. Importance of these tests are extremely critical because of the dangers emanating from flames, smoke emissions, toxicity levels in such confined areas. A sample is put into contact with a flame for a specified time frame and angle. Burn rates, burn lengths and time are carefully measured to ensure formulations meet these stringent specifications. These ROHS compliant products do not contain any substances of very high concern as per REACH.

Additionally Master Bond epoxy EP93FRHT meets vertical burn tests, smoke emission, toxic gas emission for demanding Airbus requirements. Standards are per ABD0031, Issue F, June 8, 2005 for floor and door assemblies, frame linings, internal panels. Post cure will optimize properties. Serviceability of this product is from -80°F to +400°F. EP93FRHT has outstanding electrical insulative characteristics and can be used for potting. Master Bond EP90FR-V passes Boeing Standard B7238 Revision C for low smoke density and BSS7239 Revision A for low toxicity. It also meets FAR 25.853(a) vertical burn test/specification. It can be conveniently processed and has low shrinkage upon cure.

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Flame Retardant Epoxies

EP90FR-H

Two component high strength flame retardant epoxy system. Meets stringent horizontal burn test portion of the FAR standard 14 CFR 25.853(a). Non-halogenated System. Forgiving one to one mix ratio by weight. Good electrical insulation. Serviceable from -60°F to +250°F. Low shrinkage.

EP90FR-V

Two part epoxy passes vertical burn test portion of FAR standard 14 CFR 25.853(a) for flame retardancy. Passes Boeing standard BSS 7238, Revision C for low smoke and BSS 7239, Revision A for toxicity. Bonds well to variety of substrates. One to one mix ratio by weight. Moderate viscosity. Serviceable from -60°F to +250°F. Excellent electrical insulator. Non-halogenated system.

EP90FR-HFL

Toughened epoxy system complies with FAR standard 14CFR 25.853(a) for flame retardancy. Bonding, sealing, coating, potting compound. Passes horizontal burn test specification. Withstands mechanical shock and vibration. Thermal cycling resistant. Non-halogenated type system. Bonds well to dissimilar substrates. Serviceable from -60°F to +250°F. Impressive electircal insulator.

EP93FRHT

Two part epoxy system that passes Airbus specifications for flame resistance, smoke density and toxicity. Bonds well to a variety of substrates including metals, composites, glass, ceramic and many plastics. One to one mix ratio by weight. Moderate viscosity. Service operating temperature range from -80°F to +400°F. Excellent electrical insulator. Non-halogenated system.

EP36FR

Flame retardant B-stage toughened epoxy. One part system. Ideal for potting and encapsulation. Capable of withstanding rigorous thermal shocks. Serviceable from -100°F to +500°F. Available in 30 gram cookies.

EP21FRNS-2

Durable potting, encapsulation, casting compound meets UV 94V-0 flame retardant specifications. Convenient one to one mix ratio by weight. Features a non-halogen filler. Superb flow properties. Outstanding electrical insulation. Low smoke generation. Serviceable from -51°C to +90°C.

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Latest Developments

Case Study

EP114: Utilized to produce nanocomposites via vacuum infiltration

Master Bond EP114 is a two-component nano silica filled epoxy system which offers excellent dimensional stability and a very high glass transition temperature (Tg > 200°C upon curing. Its ultra-low initial mixed viscosity (500–1500 cps at room temperature) can be further reduced by preheating to a slightly higher temperature, making EP114 ideal for vacuum infiltration to produce dense nanocomposites, as shown in the case study below.

EP42HT-2ND-2Med Black Two Part Epoxy System

Technical Data Sheet Excerpt

EP42HT-2ND-2Med Black Product Information

Two component epoxy paste adhesive. Resists sterilization exposure. USP Class VI approved. Outstanding thermal stability and electrical insulation properties. Cures at ambient temperatures. Withstands multiple cycles of autoclaving, radiation, EtO and chemical sterilants. Post curing is recommended to optimize physical properties. Serviceable from -60°F to +450°F.

White Paper

Epoxy Compounds Get Even Tougher

With adhesive products, high performance and rigidity are often thought to go hand in hand. And it is true that the very best strength, thermal, chemical and electrical properties tend to be found in rigid compounds, especially epoxies. Yet there is a growing class of adhesives, sealants and coatings that add ductility to the long list of desirable epoxy properties. Master Bond’s white paper examines the use of these toughened epoxies.

White Paper

Spotlight on Silicones

Silicone adhesive systems have several important performance characteristics that distinguish them from other adhesive families. Learn more about their unique combination of flexibility, high temperature resistance, and more specialized engineering properties.

White Paper

Electrically Conductive Adhesives Make Right Connections

As electronic circuits become more complex, engineers are finding new ways to assemble and package them. Electrically conductive adhesives provide durable bonds with conductive paths to suit a variety of electronics applications. They can be engineered to combine bond strength and electrical conductivity with other service-critical properties.

Technical Data Sheet Excerpt

EP37-3FLF Product Information

Highly flexible, low viscosity, optically clear adhesive. Resistant to severe thermal cycling and thermal shock. Bonds well to dissimilar substrates. Low exotherm system. Long working life. Superior electrical insulation properties. Service temperature range from 4K to +250°F. One to one mix ratio by weight or volume.

Lab Report

Testing Adhesives for Resistance to Xylene

Many Master Bond epoxy systems are formulated with superior chemical resistance. In the lab, we continually test our materials by exposing them to specific chemicals over a long period of time. A common way of testing the chemical compatibility of an epoxy is immersing a sample in a chemical and measuring its change in weight over time. A significant loss or gain in weight would indicate a decreased ability of a material to stand up to chemical exposure. These tests allow us to more accurately recommend the right adhesive based on specific application requirements.In this experiment, we focused on testing our epoxies for their resistance to xylene. The compounds Master Bond used for testing are a variety of two component epoxies and one component UV curing systems with good overall chemical resistance. For the first round of testing the products tested were EP41S-5LV, EP42HT-2AO-1, EP46HT-2AO Black, UV16, UV22DC80-1, and UV26. For the second round of testing the products tested were EP125, EP42HT-2 and UV25. For the final round the products tested were EP41S-5, EP41S-1HT, EP62-1HT and EP62-1. These were compared against the resistance of a generic or standard non-chemically resistant epoxy. A few thin castings, roughly 2 inches in diameter and around 0.125 inches thick, were made for each product and cured in accordance to their specifications. Once the cured samples were created and initial weight was recorded, we submerged them in xylene. Then we continued recording weekly weight measurements. We carried on these tests with frequent weight recording for varying lengths of time based on the products performance. Below you will see the results for soaking results for around 10 months in the first batch, 2 years for the next batch, and greater than 2.5 years for the third batch of products. The castings were weighed periodically and the graphs shown below demonstrate the percentage of weight change over time.For the purpose of comparison, please notice that for each testing timeframe, a casting of a standard epoxy was also tested under these same conditions which served as a reference. As can be seen in the graphs, the standard epoxy was not as resistant to xylene as the other epoxies tested. It demonstrated a significantly greater change in weight over time, and the casting ultimately dissolved in xylene after 15 weeks.In general, a swelling of less than 4-5% can be considered excellent, especially since this test may be more rigorous compared to actual service conditions. It is also worth noting that in the context of a bonded joint or a potted assembly the exposure to xylene might not be as severe or direct as in the above test conditions.Please note, when choosing an epoxy for an application where the resistance to xylene is critical, many other factors must be considered in addition to the chemical resistance. Each of the epoxies in the charts above offers a distinct set of performance properties. For example, if thermal conductivity and high temperature resistance are needed, EP46HT-2AO Black may be a good option. If a fast cure is required and there is full access to a light source with no shadows, UV26 can be considered. For longer term exposure to xylene over several months to a year or longer, the likes of UV25, EP125 EP41S-5, and EP62-1 are excellent candidates. They all need to be processed or cured differently and although some of them can be cured at room temperature alone, for enhancing/optimizing chemical resistance especially to xylene, it is critical to add heat.Disclaimer: The findings in this article are not meant to be used for specification purposes.

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