Industrial and Manufacturing Applications for Epoxy Adhesives
High-performance epoxy adhesives hold the modern world together. These versatile thermoset polymers have fascinated chemists for more than a century, but they have found a permanent home in industrial manufacturing. Epoxy is a true supermaterial with durable cross-linked bonds that resist moisture, solvents and corrosive elements. Specialized formulas can even conduct heat and provide electrical insulation while protecting microcomponents from thermal shock and debris. Epoxy is one of the most versatile adhesives available today.
Epoxy Adhesives in Manufacturing
Epoxy adhesives are used throughout the manufacturing industry. They’re found in everyday products like cellphones and cars as well as specialized aircraft and space vehicles. For industrial engineers, epoxy adhesives support freedom of design by creating a versatile, nondestructive bond that doesn’t structurally alter materials like rivets and conventional fasteners do. Additionally, epoxies require minimal equipment for adhesive application and curing, which can reduce production costs.
Thanks to the variety of formulas and convenient dispensing systems, epoxy adhesives excel in all major industries. They’re instrumental for producing a wide variety of innovative materials, such as impact-resistant carbon fiber and eco-friendly composites. One of the main advantages of epoxy-type adhesives is their ability to bond with similar and dissimilar substrates, including the following.
Types of Epoxy Adhesives
Resin-based adhesives are highly specialized. Engineers have developed formulas for specific manufacturing procedures, such as bonding, sealing, filling, potting and encapsulating. Despite the diverse array of options, there are essentially two types of epoxy.
Single-component epoxies typically require a secondary heat source to complete the thermosetting process. However, some resins may react at room temperature or in the presence of ambient moisture.
Two-component formulas cure at room temperature once a catalyst is added. Preloaded dispensers that mix resins and initiators on demand provide added convenience while minimizing the need for costly heat-setting equipment.
Epoxy Adhesive Curing Systems
Epoxy adhesives are also categorized according to their curing mechanism. The most common curing systems include heat, UV light and chemical initiators.
- Heat-cured adhesives include single-component formulas that react at temperatures above 150 degrees Celsius (302 F). These formulas require a tunnel oven or industrial kiln to maintain constant temperatures. However, the curing process can be completed quickly, and raw materials don’t require refrigeration or dry-ice packing.
- Reactive adhesives rely on a monomer resin and a separate catalyst to form a permanent chemical bond. This system is convenient because it doesn’t require extra heating or refrigeration equipment. Common ingredients used in two-part adhesives include bisphenol-A, polyamine and thiols like mercaptan.
- Light-cured epoxy adhesives contain photosensitive ingredients that form covalent or noncovalent bonds when exposed to ultraviolet radiation or visible light waves. These single-component formulas typically contain organic UV absorbers, such as Tinuvin variants. Some products may require moisture or a secondary heat treatment to complete the curing process.
Worklife and Curing Times
Epoxy adhesives have been developed for nearly every manufacturing and technical application imaginable. One of the main differences between formulas is product worklife. Depending on the chemical composition, the cross-linking process may begin within minutes or occur over 24 hours or more. It takes up to a week for some slow-curing systems to reach full hardness although snap-cure options are also available.
Compatible worklife selections based on the estimated duration of manufacturing procedures ensure that technicians and automated machines have enough time to complete required tasks. This also minimizes excessive curing times that could lead to quality concerns or imperfections due to subsequent handling. Fortunately, manufacturers have developed epoxies for a variety of specialized applications, including high- and low-temperature environments.
Epoxy Adhesive Traits and Selection Criteria
In addition to curing and worklife times, engineers must consider the product’s viscosity, hardness and strength. These factors can affect the application process as well as the durability of the finished product.
Epoxy resins and initiators range from inflexible putties to free-flowing liquids. Centipoise ratings start around 2,500 for low-viscosity formulas and go up to 20,000 or more. Product selections are based on materials handling, mixing and application considerations.
The hardness of cured epoxy is measured according to ASTM D2240 standards. Typical Shore ratings for unmodified single-part epoxies are in the 80-90 range. Ultra-flexible two-part adhesives that contain modifiers have ratings below 55.
Peel and shear tests performed according to ASTM D2393 standards measure the strength of lap bonds that will be subject to mechanical stress. Newer adhesives, including some mercaptan-based formulas, offer faster curing times along with strength ratings above 4,000 psi.
Epoxy Adhesive Uses by Industry
High-performance epoxy adhesives create a reliable, long-lasting bond that can withstand harsh solvents, subzero temperatures and extreme heat. From a manufacturing standpoint, epoxies offer a convenient, cost-effective alternative to welding when securing microelectronics on printed circuit boards or bonding large structural panels. These adhesives are used across the manufacturing sector.
Epoxies are vital for making microprocessors, printed circuit boards and photovoltaics. They’re also useful for encapsulating and potting electronic components that are sensitive to shock, vibration, moisture, corrosion or contaminants.
In the construction industry, structural adhesives offer a reliable alternative to conventional fasteners and a cost-effective way to bond prefabricated building panels. Epoxies are also used to make hard-wearing finishes as well as eco-friendly composites and laminates.
Epoxies excel when bonding woven or nonwoven filter substrates to a housing. These adhesives provide a complete seal that withstands moisture, solvents and high operating pressures. Epoxies are used by make air, solid and liquid filters used in the medical, industrial, automotive and consumer sectors.
Epoxy adhesives are invaluable in the aerospace industry. These products help manufacturers create fuselage components that are stronger, lighter and resist mechanical and thermal stress. They’re also used in electronics and flight control systems.
Cars, ships, freight containers and rail cars all rely on structural adhesives. Epoxies help manufacturers create lightweight, aerodynamic body components. They’re useful for laminating automotive safety glass, creating under-the-hood components and applying trims and finishes.
Epoxy Adhesives for Today’s Leading Industries
Engineers can choose from thousands of formulas with unique characteristics. There are low-odor epoxies, ultra-clear optical adhesives, food-safe epoxies for water filters and high-temperature bonding agents that resist thermal shock. Scientists are continuously developing new epoxy adhesives for specialized applications in all industries.