What is Epoxy Adhesives
Epoxy: Epoxy adhesive is a thermosetting adhesive, which uses an epoxide polymer resin combined with a hardener, that allows adhesion or joining of various surfaces that will maintain a strong, lasting bond under extreme stress or environmental conditions.
Adhesive: Is the process of sticking to surfaces or objects.
Epoxy adhesives are the most widely used type of industrial adhesive and amongst the most versatile structural adhesives. The strength of the cured product, versatility to bond to numerous materials, and ability to develop unique epoxy resin glue formulations for particular project needs contribute to their popularity.
There are many variations of the epoxy resin that control the properties of epoxy adhesives. Take movement over distance for example, if you require heat resistant, your heat resistant resin will be defined by temperature resistance compared to an epoxy resin that will be defined as flexible if you need flexibility or movement.
Production of Epoxy Adhesives
Investigating the fundamental structure of the components of an epoxy adhesive as part of a performance review is valuable. Epoxies are produced by the polymerization of a mix of resin and hardener.
While epoxy adhesives are made up of many different components, the two basic ingredients of epoxy adhesives are the epoxy resin and the curing agent.
Both additives, fillers, tougheners, plasticizers and other additives such as silane coupling agents, defoamers, and color pigments are all potential ingredients for epoxy adhesives.
| Constituent | Ingredient | Main Role |
|---|---|---|
| Primary | Epoxy resin, reactive diluent | Adhesive base |
| Primary | Curing agent or catalyst, accelerator | Curing enhancement |
| Modifying | Filler | Altering properties |
| Modifying | Toughener | Durability enhancement |
| Modifying | Plasticizer | Increase flexibility |
| Additive | Coupling Agent | Optimizes adhesion |
| Additive | Colorant | Adds color |
Table 1: Epoxy Adhesive Components
The primary production of epoxy resins primarily hinges upon the reaction between active hydrogens from phenols, alcohols, amines, and acids and epichlorohydrin (ECH), controlled under strict conditions.
Another means of producing epoxy resins, for example, cycloaliphatic epoxy resins, employs the reaction of olefins with peroxide, where the olefin undergoes oxidative cleavage.
The first commercially produced epoxy resin was bisphenol A diglycidyl ether (more commonly referred to as bisphenol A type epoxy resin) which remains by far the most widely produced epoxide resin (approximately 75% by volume of commercial epoxy resin is the bisphenol A type epoxy resin).
The bisphenol A type epoxy resin and hence epoxy adhesives based on the resin are useful types since the general chemical structure with numerous functional groups and essential properties.
Curing begins with the mixing of the resin and the delivery of the hardener; at this point, an exothermic process will commence as molecular chains begin to engage chemically active sites.
The covalent bond formed between the epoxy groups from the epoxy resin and amine groups from the hardener allows the polymer to cross-link, which results in an increase in rigidity and strength of the epoxy.
By changing conditions for curing like temperature, and resin and hardener specifications, the mechanical strength and resistance properties can be adjusted to meet end application and working environments.
Epoxy adhesives bond to endless material types, and properties vary by the chemistry of the system and the type of cross-linking that exists for that system.
Epoxies have good chemical and heat resistance, and they provide excellent adhesion, and water resistance, plus mechanical and electrical insulation properties.
Epoxy types of adhesives are the most common type of structural adhesives. Epoxy types are available in either one or two-component systems.
One-component epoxies typically cure in the 250°F to 300°F range which yields products with great strength, good bonding to metal, good environmental and chemical resistance, and are often the preferred choice in place of welding and riveting.
A one-component system that is pre-catalyzed will cure with mild heat and offers a high rate of utility while minimizing air entrapment which can lead to problems with bonding effectiveness or variability.
The equal cure time for one-component systems compared to two-component systems is shorter. A two-component epoxy may require ambient temperature catalyzation, but heat alone will enhance cross-linking, and corresponding properties.
Two-component solutions are very flexible and compatible with nearly every substrate while also being able to sustain normal weight or unloading over a period of time. Being so versatile and resistant to physical and chemical actors is what makes these two-component solutions so stable.
These epoxies too are versatile in that they have many industrial applications, bonding/sealing, coatings and encapsulation, as well as many industries, electronic, medical devices and aerospace.
There are also other formulations that can provide capabilities beyond the usual capabilities of bonding like flame retardancy, cryogenic and rapid cures and more high temperature resistance.
Factors to Consider When Selecting Epoxy Adhesives
Some crucial factors to keep in mind when selecting epoxy adhesives are:
Adhesive Substrates
- What substrate needs bonding?
- Is it metal, wood, or specific types of plastic?
- Are the areas large or small?
- Are the bonding surfaces similar or varying?
An adhesive must adequately ‘wet out’ the surface, leading to an adequate degree of surface coverage, thereby maximizing the surface area accessed by the adhesive and creating the greatest surface contact (surface area) and bonding strength of the adhesive to the substrate.
Joint and Load Design
There are some important design considerations to remember when designing an adhesive joint:
- The joint should maximize shear forces and minimize peeling and cleavage forces.
- If possible, total compression is preferred to tensile forces.
- The width of the joint is always more important than the length of any overlap.
Environmental Conditions
The strength of the bond is affected by a multitude of factors, e.g., temperature, moisture, chemicals, and weathering. Ideally the candidate adhesives will be tested in environments that simulate the service conditions when these factors may have a detrimental effect.
Adhesion Properties
- Flexible adhesives perform well in cases where peel, impact, or thermal shock applies as well as when they are on surfaces that are expanding or contracting due to thermal loading.
- Rigid or more rigid adhesives are generally better for heat and chemical resistance, tensile strength, and lower creep.
Application Techniques
Describing adhesives takes preparation, performance, and the application method into account. How will the adhesive be applied? A single or dual component system?
Planning the dispensing, mixing, and application approaches early will save significant time and cost while avoiding any delays in production.
Adhesive Testing
Ultimately, evaluating adhesives is a process of selecting and testing multiple candidates for the application and examining properties with standards tests. Sampling and trying is the best way to make an informed decision.
Curing Time
Establishing an appropriate cure is key to obtaining the best performance from adhesive. There are several things to consider:
While some epoxies, silicones, and polyurethanes can cure at room temperature, some will need elevated temperatures – and can the application tolerate that much heat?
UV-cured adhesives are one-component systems that cure very quickly under specific wavelengths and light intensities. This is especially relevant when the bond lines are being bonded where glass, or plastic, can pass UV, or visible light for the adhesive to cure.
Packaging Options
Epoxies are typically packaged, mixed, and applied when necessary to ensure shelf life and limit waste. Static mixers in dual-barrel cartridges help dispensing the premixed components in the correct ratios for equal application quality.
In the realm of electronics, premixed frozen epoxies are also common, and need to be defrosted and mixed right before use.
Resistance to Chemicals and Flames
In certain applications, resistance to chemicals and fire is of paramount importance; a key characteristic of epoxies is their resistance to a wide range of substances such as acids, bases, solvents, fuels, and fluids – both salt and fresh – suitable for environments exposed to harsh chemicals.
Some epoxies also meet flammability ratings for uses that require strict specification (i.e. Underwriters Laboratories, an independent safety certification organization for public safety concerns), in fact, specialty epoxies have been developed to extend product life in harsh environments.
Conductivity of Electricity and Heat
Epoxies are frequently used to bond electronic and electromechanical assemblies in situations where electrical or thermal conduction capabilities are essential.
These adhesives can be used to bond heat sinks to components producing thermal energy when operating with the goal for better heat distribution for operational effectiveness.
Electrically conductive epoxies establish bonded connections requiring electric conductivity for signal transfer or static discharge, making the creation of reliable, high-performance devices easier for the design and process engineer.
Classes and Types of Epoxy Adhesives
This chapter investigates the different classes and types of epoxy adhesives available today. Epoxy adhesive technology is a valuable, efficient, and versatile technology that offers excellent bond strength, chemical resistance, and versatility with a wide range of materials.
Epoxy adhesives are important in construction, automotive manufacturing, aerospace, electronics assembly, do-it-yourself repairs, and many other fields.
By understanding the different classes of epoxy adhesives and the different specialty formulations that are available, users will be able to identify the best epoxy adhesive solution for their application and create reliable bonds that last, even when exposed to severe environmental conditions.
Classes of Epoxy Adhesives
Epoxy adhesives can be classified into two categories epoxy glue systems (1 component or 2 component) and make solid and definitively strong bonds.
The differences are mainly associated with curing mechanism, the way they are mixed or applied, and their end-use attributes. While these types of structural adhesives can be selected for high performance and durability characteristics in industrial and commercial applications.
Two-component epoxy resin adhesives generally provide greater mechanical strength, long-term durability, and high resistance to chemicals compared to a one-component epoxy adhesive.
Therefore, two-component epoxies are generally the best choice where high strength bonding is necessary, or adhesion applied as a structural adhesive, or if the adhesive is applied as expensive protection and the load carrying capability and needs were a factor along with thermal stability.
2K Epoxy Adhesive or 2 Component Epoxy Adhesive
Before use, both components of a 2Q (two-component) epoxy resin adhesive (the resin and the hardener or catalyst) must be mixed thoroughly.
The adhesive cures through a chemical reaction between the two components, forming a space filling, rigid, and cross-linked solid structure with high adhesive strength.
2Q epoxy adhesives have increased versatility, capable of being used across all of the market segments including automotive, aerospace, marine, electronics, construction, and general manufacturing industries.
They can be slightly more complicated to use, as they require mixing prior to application, and the working (pot) life (the time before the adhesive cures) will vary from a few minutes to a few hours dependent upon the formulation of industrial epoxy adhesive.
2K epoxy resin adhesives typically cure at room temperature, although some can cure faster with some heat and/or other energy sources like ultraviolet (UV) light.
Engineers define the strongest and most durable epoxy bond when cure times are longer. Thus, these adhesives use in applications that require structural integrity, gap filling, and resistance to mechanical stress, impact, and vibration.
2K epoxy glue systems bond well to almost any substrate, including wood, metals (steel and aluminum), plastics (ABS, and PVC), ceramics, composites, and multiple types of rubber.
They are highly resistant to physical and chemical exposure (solvents and moisture) and can tolerate operating temperatures from 95 to 200°C (200 to 390℉).
All of this enables their widespread use for industrial adhesive applications in the high-end, demanding category, and in heavy-duty repair and maintenance operations.
Single Component Epoxy Adhesives
One-component epoxy resin adhesives, as opposed to 2K epoxy glue, come pre-mixed, and are ready to apply with no mixing associated with their use.
Typically, they are either paste-like or thixotropic, thereby they can be applied using a trowel, syringed, or extruded in return beads, this is an attractive dispensing method, especially for automatic means.
They are designed to cure or set at elevated temperatures, depending on chemical configuration and design of the resin adhesive, typically the temperature cures as low as 120°C to as high as 175°C.
One-part epoxy heat cured adhesive systems are capable of effectively and efficiently filling and sealing gaps between closely spaced surfaces of solid material, particularly metal, under hyperstress.
These products as commercially available are normally developed and sold as heat curing epoxy films or sheets, therefore, they are particularly advantageous for use when bonding or laminating larger items.
They are often diabetic material epoxy adhesives favoured in aerospace and automotive applications, owing to their ease of use, gap filling utility, and robustness and apparent usefulness of these adhesives for structural bonding circumstances.
In addition to their usefulness for aerospace structural bond processes, resulting adhesive functionality and performance provided by this class of adhesive, is also an additional reason they are embraced with some degree of perfection in construction for uses as durable tile adhesives, flooring installation, and the potting of electrical components.
Excepting timing, the very high bonding strength, chemical resistance, thermally resistant, processability, and ease of use are determining factors causing large acceptance for a wide variety of uses; and consequently their high speed and repeatability in bonding always display value.
Therefore, these adhesive materials are also a staple in the production of assembly line and precision-type manufacture.
Types of Epoxy Adhesives
There are many types of epoxy adhesives, both standard and specialized that are designed for specific bonding situations, performance qualities, and environmental conditions.
DGEBA Epoxy Resin
DGEBA epoxy, mainly, diglycidyl ether of bisphenol A (BPA), is the first and most common adhesive-grade epoxy resin. As the base resin, DGEBA has a low cost of raw materials and is compatible with many catalysts, and it has been used as part of many adhesives.
DGEBA adhesives are widely used in the electronics, automotive, construction, and marine industries as they provide strong, durable bonds with good chemical resistance.
Industrial adhesives based on DGEBA epoxy can be formulated to cure at room temperature, or to be cured by applied heat, meeting the requirements of a wide variety of manufacturing needs.
DGEBA resins are available in low molecular weight liquid, semi-solid, and solid forms. For example, DGEBA epoxy resins can be brominated for flame-retardant applications such as circuit boards and electrical insulation.
Overall, the DGEBA epoxy adhesives are the most preferred because they can be used in many applications, they can be customized, and they have a reasonable balance of the various performance characteristics.
Waterborne Epoxy Adhesives
Waterborne epoxy adhesives, also referred to as aqueous or water-based epoxies, are a new development for users looking for low-VOC, environmentally friendly adhesives. Epoxies are typically hydrophobic and do not dissolve in water.
However, chemical modification and/or emulsification with surfactants allows for resins to disperse in aqueous systems.
Generally, water-based epoxy adhesives provide strong, reliable bonds with much lower environmental impact—this is especially important when looking at green building certifications, or if the manufacturer wants to be more environmentally conscious.
The final mechanical and chemical stability depends on both the surfactant used and the processing method for emulsification.
Epoxy Acrylate Resins
Epoxy acrylate resin adhesives, which include vinyl ester and specialty UV-curable resins, are hybrids of epoxy and polyester chemistries. Epoxy acrylate resins cure rapidly at room temperature and can be toughened by peroxides or triggered by radiation (UV/EB).
They have several advantages to conventional epoxy glues including lower viscosity, greater flexibility, better wetting, and rapid cure time (although they can have greater cure shrink).
Current industry uses for epoxy acrylate adhesives are flooring, protective coatings, composites and rapid cures where speed and toughness matter.
Flexible Epoxy Resin Glues
Conventional epoxy adhesives are recognized for their rigidity and strength but provide little toughness (the ability to absorb impact/load) or strain when these properties are required within a specific adhesive application.
Long-chain aliphatic epoxies can be blended into formulations to provide flexibility and still retain sufficiently strong cohesive bonds.
These flexible or ductile epoxy adhesives are commonly used for laminates of safety glass, sound and vibration damping, encapsulating sensitive electronic products, and bonding material that will undergo temperature change or dynamic loads.
These flexible epoxy adhesives provide a balanced hardness to elongation, meeting both the design and production needs of today— making them a critical portion of industrial and consumer adhesive products.
Epoxy Novolac Adhesives
Epoxy novolac adhesives exhibit excellent resistance to chemicals and superior high-temperature performance.
Compared to standard BPA epoxies, there is a significantly higher cross-link density compared to regular BPA epoxies affording a greater level of protection against aggressive chemicals, acids, and thermal cycling.
What this means is that a high-grade epoxy novolac is balanced between chemical processing applications, pipelines, coatings, and electronics.
Other than requiring cured temperatures that are higher than a regular epoxy, they can also be processed at room temperature depending on their application.
Modern developments have addressed certain issues, including high viscosity and how that could hinder usability for so many options for processing and substrate applications with these high-performance epoxy adhesives.
Epoxy novolacs are most available in a two-component (2K) product employing much tighter controls to allow the greatest level of chemical and thermal stability in the most demanding industrial use.
Epoxy Adhesives That Cure at Room Temperature
Epoxy adhesives that cure at room temperature, typically packaged as two-component systems, are effective, versatile, and easy to use adhesives that exhibit their full mechanical properties quickly and without the use of special heating equipment.
The epoxy resin two-part system consists of the epoxy resin or base material mixed with its curing agent (hardener), which initiates a cross-linking chemical reaction that forms a hard thermoset bond that is strongly adhered to a substrate (metals, composites, wood or plastics).
A formulator can manipulate the pot life, open time, final properties, etc., and therefore, these products are ideal for field repairs, maintenance and general purpose bonding at ambient temperature conditions.
Epoxy Adhesives That Dry at Ambient Temperature
Fast-curing, room temperature epoxy adhesives often use mercaptans or tertiary amine accelerators to drastically reduce fixture and cure times.
These systems provide excellent adhesion and a strong bond within 15 to 30 minutes when there is a need for rapid strength development. This can occur in scenarios such as quick repairs, emergency repairs, as well as assembly-line production.
Full cure is typically acheived in 24 hours. Good will on behalf of the user is also necessary because the working life of these high-speed epoxy glues is limited.
Epoxy Adhesives That Cure at Room Temperature
Aliphatic polyamines are frequently utilized as curing agents in epoxy adhesive formulations for ambient curing.
Modified polyamine hardeners allow cross-linking of epoxides, which allows the producer of adhesive products to modify aspects including cure speed, bond toughness, and usability.
This flexibility allows epoxy resin adhesives to accommodate various industrial, automotive, aerospace and even DIY adhesive applications where temperature-sensitive substrates or rapid deployment is required.
Epoxy Adhesives That Cure in the Sun
UV-curable epoxy adhesives revolutionize high-speed assembly and manufacture simple electronic devices by offering an instant cure, as well as very strong and reliable bonds with minimal exposure to ultraviolet radiation.
This enables great opportunities in many value-added areas, especially electronics assembly, image sensor module assembly, touch panel and display assembly, and any application that requires high throughput and great adhesive performance in cleanroom or production environments.
A recent shift to UV-cationic and UV-acrylate hybrid formulations has revolutionized production, and expanded the options available for instant-cure epoxy adhesives into more complex and critical applications.
UV cure epoxies are free of oxygen inhibition, have limited shrinkage during cure, and have better adhesion compared to regular acrylate UV adhesives used in optical or medical device bonding.
UV Cationic Epoxy Adhesives
UV cationic epoxy adhesives contain cycloaliphatic epoxy resins and photo-initiators that rapidly cure to strong acids upon exposure to ultraviolet light. The strong acids rapidly initiate fast cationic polymerization.
Structure adhesives have low cure shrinkage and do not have a surface cure like free-radical systems. This means that UV cationic epoxy adhesives can create strong accurate bubble-free bonds in assembled optoelectronic electronic and microelectronic components and assemblies.
Usually UV cationic epoxy adhesives may post-cure thermally after UV exposure to reach its full strength or to bond some substrates. The intent is to ensure the bond will have the best durability and performance, particularly in the case of bonded mission-critical or safety-related components.
UV Hybrid Epoxy Adhesives
Hybrid UV and thermal cure epoxy adhesives combine features of both extremes in adhesive curing. Effective UV acrylate adhesives offer instant cure and thermally cured epoxies provide the best in the industry.
This new adhesive category has been developed in order to remove all of the issues that typically plague normal UV adhesives, such as surface cure, shadows and not curing as a unit, as in chemical shrinkage etc.
The use of a hybrid process not only provides a permanent bond with better cure results, but ultimately has greater final bond strength and durability in aggressive environments.
Typical ingredients in hybrid adhesives would be acrylic monomers, epoxy resins, light reactive initiators, curing agents for the epoxy. Some hybrid adhesive contains thermal initiators like peroxide to ensure that a cure occurs in the spots where the UV light cannot provide penetration.
The use of hybrid adhesives is preferred because of the speed of processing and general performance during production-in production lines, microelectronics, optical devices, repairs and assembly.
As a result of its reliability, and overall performance, epoxy adhesive products are now widely used for bonding, sealing and encapsulating in virtually every major industry.
The user is encouraged to evaluate several factors when selecting an epoxy adhesive With variables such as substrate type, environmental exposure, service temperature, mechanical load, and cure profiles in order to ensure the best bonding structures will result.
Major suppliers or manufactures using epoxy adhesive, are usually able to offer a wide selection of epoxy adhesive formulations, including custom formulations for specific technical needs.
Applications and Benefits of Epoxy Adhesives
This chapter will discuss the applications and benefits of epoxy adhesives.
Applications of Epoxy Adhesives
The applications of epoxy adhesives include:
- Commonly used is epoxy adhesives where extreme chemical exposure takes place as a matter of course due to there great chemical resistance characteristics. When chemicals are typically stored they are in tanks and containers with an epoxy novolac based formulations.
- Automotive Sector: The automotive sector is heavily dependent on the dependable use of epoxy adhesive in replacement of mechanical fasteners and welds, where reduce weight is a consideration. Typical uses are using flexible epoxy resin adhesive with a level component (symmetrically) and/or some vibration or structure where a vibration destructive mechanism is to be expected.
- Aerospace: The aerospace sector use epoxy adhesives into either one component films and 2K epoxy glue for the many factual reasons. One example to eascape is helicopter rotor blade adhesive epoxy glue, the actual physical and mechanial properties of the glue is no comparsion to any normal situational bonding product.
- Marine: Epoxy resins are suital for marine applications in that they create a watertight bond and provide tolerable chemical resistance in salt-water applications, including bonding substrates in various marine conditions.
- Builders: the Builders and construction industry, and domestic uses to repair broken tiles and concrete floors use epoxy adhesive for its bonding durability, and also good weather resistant adhesion properties make it great for external outdoor loads, and construction bonding applications.
- A majority of builders consider a construction epoxy adhesive as a premium quality and first choice of adhesive for also very popular to DIY projects.
Benefits of Epoxy Adhesives
The benefits of epoxy adhesives include:
- The mechanical characteristics are outstanding. Epoxy resins display a very good cohesivity and their chemical structure is compact.
- Outstanding bonding excellent properties achieve with ease.
- Little curing volume shrinkage. The linear expansion coefficient is very low so is the internal stress.
- Great finishes. Volatiles of low molecular weight hardly appear during and after curing.
- Electrical performance is excellent.
- Stability is excellent. Free from contaminants such as salt and alkali, stable – does not air degrade.
- General heat resistance.
Advantages of 2 Component Over Single Component Adhesives
- Temperature Bonding: Because two-part epoxy can cure at room temperature, it is not always necessary to heat it. Depending on the curing methods, it may take five to eight hours to obtain handling strength at room temperature. You can also speed up the reaction of the resin and hardener using a chemical catalyst or heat.
- Perfect for Industry: If an industry uses adhesives at all, it more than likely has used a two-part epoxy at least once. two-part epoxies are also suitable for assembly, applications, and repairs within industries such as marine, automotive, aerospace, aviation, railway, appliance, electronics, electrical, plumbing, HVAC, manufacturing, construction, etc., because of their strength and versatility.
- Managing Different Environments: Because two-part epoxies can resist oil, moisture, and even a variety of solvents, there is a broad spectrum of applications with which to work within. In fact, they were designed for high-stressed applications with extreme temperature variations, torturous vibrations, and mechanical shock.
- Shear and Tension Resistance: Two-part epoxies have high shear strength, which means they are able to resist external forces that try to make the adhesive internal structure slide against itself. They also have a high tensile strength – the ability to resist failing when subjected to stretching or pulling to rupture.
- No Wasted Substrate: Assemblers can glue literally anything to almost anything else with two-part epoxies.The bonding phenomenon of a two-part epoxy results in a chemical reaction that is so strong that at the end of the cure, the two-part epoxies, are indistinguishable from a uniquely formulated material that is as strong as molded plastic. While it is somewhat attributable to the unique formulation of the two-part epoxies, the key distinguishing feature of the two-part epoxies in comparison to a one-component adhesive is bond strength. In addition to bonding plastics and elastomers that have never been treated, two-part epoxies will bond rubber, metal, wood, glass, plastics, masonry, and virtually any other substrate, as two-part epoxies are available in many formulations and can be modified relatively easily.
- Forms and Functions: Two-part epoxies are available in liquid, paste, semi-cured film and solid forms. In addition to excellent adhesion, two-part epoxies can also be used to fill gaps, they provide excellent electrical insulation and have a high degree of chemical inertness (i.e. will not adversely react to specified substances).
- Dimensional Strength: The bond strengths of two-part epoxies to many different types of substrates are well documented. The chemical structure involved with a two-part system contributes to that bond strength. The capacity to absorb or tolerate substantial modifications is another dimension of bond strength. When we mix a resin and hardener for the purpose of bonding, we now have an epoxy. The hardener increases polymerization, which is the chemical reaction that links all the monomer molecules together to form polymer chains, known as curing. The bonding is a reaction that demonstrates the bond strength of the two-part epoxies over one-component epoxies.
- Cumulative Modifications: Arguably, the most conspicuous benefit of two-part epoxies is the ability to modify the two-part epoxy with pigments, fillers and others resins to alter such properties as viscosity, bond strength, flexibility, etc. The reason why we wanted to conclude with this advantage is it is arguably, when we think of two-part epoxies, the gift that keeps on giving. Certainly, two-part epoxy has an array of advantages that can be practical for many circumstances.
Drawbacks of Epoxy Adhesives
The drawbacks of epoxy adhesives include:
- It may be brittle without modification.
- It has a thermal stability at 185- 200 °C
- Components may be harmful if not careful
- Cure epoxies can also be brittle unless modified.
- There is an exact mix ratio for curing two part epoxies.
- Cure times are long.
Conclusion
Epoxy adhesives demonstrate superb adhesion to many surfaces and offer the most common types of structural adhesives available.
A variety of epoxy adhesives can be cured at room temperature, elevated temperatures, or with the use of UV light depending on the curing agent which is used.
There is a plethora of epoxy adhesives, either one-part or two-part, that have been commercialized and utilized in industrial production and applications, the bonding of metals, concrete, glass, ceramics, concrete, a large variety of plastics, wood, and many other materials.