Adhesives are non-metallic materials used to join surfaces permanently through an adhesive process. Using adhesives allows construction workers to bind materials together and distribute load stress evenly across a joint cost-effectively. So, what are the common types of adhesives used in construction?
The main types of adhesives used in construction include polymer adhesives, acrylic adhesives, hot melt adhesives, resin adhesives, and anaerobic adhesives. Electrically conductive adhesives, pressure adhesives, reactive adhesives, and plastisol adhesives are also types of construction adhesives.
In this read, we’ll analyze the different types of adhesives used in construction, shedding light on each type’s pros and cons, and how they’re used in construction.
1. Hot Melt Adhesives
A hot melt adhesive (HMA) is a thermoplastic adhesive commonly sold as cylindrical sticks of varying diameters. The sticks are designed to be placed on a hot glue gun with a continuous-duty heating element.
Compared to other types of adhesives, they have a longer shelf life and can be easily disposed of without the need for special precautions. They also have a reduced number of organic compounds and don’t need any curing time.
In the construction industry, they are used in product assembly, profile-wrapping, and laminating applications in woodwork. They are also used in the installation of electronic devices, especially when affixing wires.
2. Acrylic Adhesives
Acrylic adhesives are resin-based adhesives composed of methacrylic or acrylic polymers. An acrylic adhesive is extremely strong and efficient in making multiple bonds. It’s preferred in the construction industry due to its resistance to environmental elements like excessive sun and rainfall.
In terms of strength and ability to hold items, not too many adhesives compare to acrylic adhesives. This is due to the high cohesion and adhesion properties of acrylic adhesives, which ensure items are held well in place.Acrylic adhesives come in both paste and liquid forms. Liquid acrylic adhesives are applied using a brush or damp cloth and are mostly used for carpentry or upholstery applications or hard to reach areas during construction. Paste acrylic adhesives are commonly used in day-to-day construction projects and are known to make strong bonds.
3. Epoxy Resin Adhesives
Epoxy resin adhesives are well-known for their dimensional stability, high mechanical strength, chemical resistance, and affordability. The strength of epoxy adhesives makes it a great option when bonding steels, non-ferrous metals, aluminum, fiber-reinforced composites, ceramics, bricks, foamed structures, glasses, and woods.
Epoxy adhesive systems consist of a base resin, an accelerator, a hardener, fillers, flexibilizers, additives, and diluents. The base resin used in the production of epoxy resin adhesives determines its chemical resistance and thermal stability.
The durability, high tensile, and shear strength of epoxy adhesives make it a great option for light and heavy construction work. Although the bonds made with epoxies are usually rigid, they can be made more flexible by altering the components used in production.
When epoxy adhesives are used to bond different metals, the bond line acts as a barrier that prevents galvanic corrosion. Epoxies are highly resistant to moisture, fuels, and chemicals, making them a great option for construction. Epoxy adhesives are also used in electric work due to their good electrical insulation properties.
Epoxy resin adhesives are available in either one part or two-part epoxy systems, which guarantees extra firm bonds are made when used in external construction or interior decoration.
4. Anaerobic Adhesives
Anaerobic adhesives are composed of dimethacrylate monomers and cures only when oxygen is absent. Compared to other types of adhesives, anaerobic adhesives are less toxic, mild, and non-corrosive to metals, features that make them ideal for usage in construction.
Besides dimethacrylate monomers, anaerobic adhesives also comprise multi-functional and monofunctional ester monomers, stabilizers, a redox radical initiator system, different types of modifiers, and resins.
Some of the main advantages of using anaerobic adhesives include low odor levels, durability, and cure-on-demand capability. However, despite their ability to make strong and lasting bonds, anaerobic adhesives are not ideal for porous surfaces and thermoplastics.
5. Pressure Adhesives
Pressure adhesives rely heavily on viscosity and elasticity to bond to a surface. As suggested by the name, pressure adhesives work when pressure is applied between the adhesive and the point of attachment.
This type of adhesive is commonly used on stickers and can’t be relied on to hold two substances together. In construction, it can come in handy in sticking cautionary notices such as danger signs or on-site instructions.
6. Electrically Conductive Adhesives
Electrically conductive adhesives are commonly used in electronic applications, more so where electrical current needs to pass between two or more items. This type of adhesive cures in under two minutes and is mostly made from 80% conductive particles.
The base adhesive is usually a 2-component epoxy, although polyester and acrylate are also common options. Conductive components used in electric conductive adhesives usually determine the overall cost. Inexpensive electrically conductive adhesives usually utilize iron, which is a poor conductor. However, expensive ones use copper or silver.
7. Plastisol Adhesives
Plastisol adhesives consist of polyvinyl chloride (PVC) particles that are dispersed in a plasticizer. They have great peel resistance and high flexibility, features that make them ideal for usage in construction. However, the main problem with plastisol adhesives is their sensitivity to shear stress. Plastisol adhesives are also susceptible to creeping when subjected to extra heavy loads.
Although highly efficient in bonding, plastisol isn’t environmentally sustainable, explaining why alternatives like epoxy resins are becoming popular. Plastisol adhesives also help to bond non-pretreated metals due to their ability to take up oil.
8. Reactive Adhesives
Also called curable or chemically hardening adhesives, reactive adhesives usually require a chemical reaction to bond two surfaces. Reactive adhesives come as one or two-component reactive adhesives. The ability to make strong bonds makes reactive adhesives ideal for heavy loads that need high strength adherence and permanency.
Besides curing fast, reactive adhesives have the capability to withstand extreme environmental conditions, making them ideal for use in external structures.
Although highly durable and strong, reactive adhesives must be applied correctly and with the right level of precision to make strong bonds. Reactive adhesives start to cure immediately when they’re exposed and may require machinery or dispensers when used in construction projects.
9. Solvent-Based Adhesives
The polymer system used in formulation determines the performance and effectiveness of solvent-based adhesives. Since most solvent-based adhesives have flammable solvents, it is important to take adequate care to eliminate the risk of fire.
Once a solvent-based adhesive is applied, the solvent evaporates (fairly quickly), which increases the adhesive film’s overall viscosity. While bonds can be made when adhesives are applied, it’s advisable to allow the solvent to evaporate and make strong bonds.
10. Thermoset Adhesives
Thermoset adhesives are thermosetting plastics or polymers that are used as adhesives. This type of adhesive is usually supplied uncured and mostly consists of unlinked monomers. Curing might be induced by applying stimuli such as light, heat, or a chemical hardener.
Most thermoset adhesives come as two-component systems made up of a resin and hardener, which are then mixed to kickstart the curing process. Curing can take just ten minutes and can even take longer than an hour.
Thermoset adhesives are well known for their high strength, resistance to heat and moisture, and impressive gap-filling ability. Although two-component adhesives are hugely popular, one-component systems are also used to form bonds between surfaces.
A great example of thermoset adhesives is epoxy, which is commonly used to bond wood due to its better gap-filling and moisture resistance properties. Epoxy resin is widely used in construction due to its ability to make strong bonds on glass and metal.
Some examples of thermoset adhesives include:
Due to their long-term stability and bonding strength, thermoset adhesives are among the most popular adhesives used in construction. They’re commonly used for heavy applications on the construction site and might need heavy machinery during application.
11. Water-Based Adhesives
Commonly referred to as waterborne adhesives, water-based adhesives are formulated from either soluble synthetic polymers or natural polymers. Soluble synthetic polymers are obtained from polymers like cellulose ethers, polyvinyl alcohol, carboxymethylcellulose, methylcellulose, and polyvinylpyrrolidone.
Natural polymers are obtained from vegetables (starches and dextrins), animals (bones and hides), and protein sources (fish, blood, casein, milk albumen, and soybean).
Water-based adhesives may be formulated as dry powders or supplied as solutions. When dealing with dry powders, it must be mixed with water before application. This is because water-based adhesives get their bonding strength when water is lost through absorption or evaporation.
The point to note, though, most water-based adhesives don’t have a long shelf-life, thus making extended storage impossible.
Although highly affordable, flexible, and strong, water-based adhesives need a bit of care to improve overall performance. These adhesives might have a strong odor and can even react when exposed to the user’s skin. However, it sets quickly and can be applied by a roll or spray, making it a convenient way to bond different surfaces during construction.
12. UV Curing Adhesives
Also referred to as light curing adhesives, UV curing adhesives use light and natural radiation to kickstart the curing process. Through free-radical chemistry, UV curing adhesives make permanent bonds without the need for external heat sources.UV curing adhesives come in different viscosity ranges and chemical systems (mostly polymer-based). These adhesives can bond a variety of substrates, including dissimilar ones, without compromising overall strength.
The versatility of UV curing adhesives makes them among the most popular options in the construction industry. It can be used to bond glass, plastic, cabinets, handles, and shower doors.
13. Phenolic Resin Adhesives
Phenolic resins are mostly manufactured as films and as liquid compositions and are made from condensing formaldehyde and phenol. Phenolic resins are commonly used to bond items due to their ability to penetrate and adhere to several fillers and reinforcements.
Phenolic resin adhesives are highly compatible with cellulose fillers, making them ideal for binding plywood, particleboard, oriented strand board (OSB), and hardboard. This type of adhesive is great for making strong bonds that are chemical and thermal resistant.
A great advantage of phenolic resin adhesives that makes them construction-suitable adhesive is their ability to maintain tight bonds even in extreme weather conditions. However, the strong bonds and resilience come at a cost as phenolic resin adhesives are among the most expensive in the market.
Advantages of Adhesive Bonding
Reduced Localized Stress
Most assembly techniques usually lead to uneven load and stress distribution. However, by applying adhesives on the surfaces that need bonding, the load is evenly distributed across the surfaces, thus reducing localized stress concentration. Adhesives also score high when it comes to fatigue resistance compared to other assembly techniques.
Superior Resistance to Mechanical Shock
Screws and nails tend to weaken over time when exposed to hostile conditions. On the other hand, adhesives, due to their unique chemical properties, can be produced to resist hostile environmental conditions, thus prolonging their useful life.
Ability to Bond Similar and Dissimilar Materials
While some assembly techniques can make strong bonds, not too many compare to adhesives when it comes to bonding dissimilar items. Adhesives can bond metals to plastic, glass to wood, and even ceramics. The unique bonding properties make adhesives a great option during construction, especially when looking to bond surfaces made from different materials.
Ease of Disassembly
Compared to other assembly techniques like mechanical fastening, adhesive bonding is easy to remove when the need arises. Removing nails and screws can compromise the structural integrity of a building, especially when extra pressure is applied in highly sensitive joints.
However, with adhesive bonding, several removal techniques are available, which help to ensure the bonded surfaces are safely detached without any damage.
Adhesive-bonded surfaces are generally more aesthetically appealing compared to mechanical fasteners. This is because, unlike rivets, adhesives don’t leave external projections and gaps. The external projections can lead to injuries, especially for exposed joints.
Adhesives are well-known for their durability and dimensional stability. With many products available in the market, it’s easy to choose one that’s best suited for different types of construction. There are adhesives meant for light construction work, while others are better suited for bonding surfaces meant to distribute heavy loads and stresses.
As observed from the above-discussed adhesives, there are several categories of adhesives, depending on the components used in construction. The availability of different products gives contractors the freedom and flexibility to choose products that best suit the nature of their projects.
Even better, technological advancements and extensive research have helped develop new recipes for extra strong and durable adhesives. Some adhesives have great electrical conductivity properties while others have impressive thermal resistance features, thus making adhesives one of the most versatile assembly products to have on a construction site.
How to Strengthen Bonds Made by Adhesives
When dealing with adhesives, it is critical to prepare the surface adequately. The need for preparing surfaces cannot be overstated, more so since surfaces are mostly contaminated with grease, dirt, moisture, oil, and other contaminants. Therefore, it is crucial to clean up the surfaces first to reduce the chances of failure during construction.
Metals like copper and aluminum form oxide layers that tenaciously cling on substrates, thereby forming favorable surfaces for applying adhesives. Glass usually requires surface treatment to make and maintain strong enough bonds. Applying adhesives in poorly prepared surfaces leads to bond failure, which can prove costly when working on highly complex joints.
Therefore, it is important to check out product details to ensure the right type of adhesive is used. This is because some projects require electrically conductive adhesives, while others work best with water-based adhesives or UV curing adhesives. As a rule of thumb, the best type of adhesive should depend on the nature of construction and the desired type of bond.
As evident from the above discussion, there is a wide range of adhesives, each of which has its unique properties. Epoxy resins, for instance, are widely used in construction work due to their weather resistance, durability, and thermal resistance.
Other types of adhesives are also ideal for construction projects, with some, like electrically conductive adhesives, allowing electric current to pass through. Therefore, when dealing with adhesives, the trick is to use products whose properties are suitable enough to make strong bonds that can withstand the test of time.