Industrial and Construction Adhesives
Various methods are used to bond and connect components and objects, each effective in different situations. With the help of various types of adhesives, we can connect and secure different materials. To do this effectively, it’s essential to understand the types of adhesives available and their specific uses. Adhesives come in various forms such as liquid, paste, tape, etc. In this article, we aim to comprehensively introduce them. Join us to explore what adhesives are and gain a complete understanding of their types and applications.
You may have used various adhesives like electrical tape or super glue in your home or workplace. However, many different types of adhesives exist, and their applications might be interesting to you. It may seem challenging to think that some components can be easily repaired or connected with glue, but by introducing different types of adhesives, you will see that specific adhesives can be conveniently used for particular materials and components.
Types of Adhesives
Different types of adhesives are available for various industrial applications. These adhesives are produced with different materials and have bonding capabilities on various substances. Construction adhesives are used for bonding materials together and sealing leaks. In our daily lives, we commonly use types of adhesives such as liquid adhesive, stone adhesive, electrical tape, welding glue, and super glue.
In the following sections, we will discuss the types of adhesives and the commonly used ones in the industry, along with their features and capabilities.
Epoxy Adhesives
Epoxies are the best-known construction adhesives with the most applications. They bond wood, metals, glass, concrete, ceramics, and hard plastics effectively and are resistant to oils, water, dilute acids, bases, and most solvents. Therefore, they are more commonly used for bonding vinyl flooring in wet areas and to metal surfaces. The most recognized construction adhesive is epoxy, often used in a standard form, created through the reaction of sodium salt from bisphenol A with epichlorohydrin. Aliphatic and aromatic amines are used as hardening agents. These adhesives bond easily to wood, concrete, glass, metals, ceramics, and hard plastics and are highly resistant to water, dilute acids, and oils. They are commonly used for bonding vinyl flooring in wet areas and to metal surfaces, and two-component epoxy adhesives are among the most widely found types in homes and industries.
Phenolic Adhesives for Metals
When phenol reacts with excess formaldehyde under alkaline conditions in an aqueous solution, a product known as resol is formed, which is an oligomer including phenols polymerized by methylene bridges on benzene rings. To prevent steam-filled cavities from forming, phenolic adhesive joints are usually cured under pressure, typically between heated wide steel plates using a hydraulic press. Due to the brittleness of phenolics, polymers such as polyvinyl formal, polyvinyl butyral, epoxies, and nitrile rubber are added to make them tougher. This liquid adhesive is based on synthetic phenolic resin and cures upon heating. It is suitable for bonding friction materials in brakes and clutches.
Formaldehyde Condensates for Wood
Some adhesives used for wood are the result of formaldehyde condensation with phenol and resorcinol (dihydroxybenzene). Others are condensed with urea or melamine.
Acrylic Adhesives
Structural adhesives containing acrylic monomers cure at ambient temperature through radical polymerization.
Anaerobic Adhesives
Anaerobic adhesives cure in the absence of oxygen, which is a polymerization inhibitor. These adhesives are often based on dimethacrylates from polyethylene glycol. Their applications typically include bonding gears, locking threads, reinforcing cylindrical joints, and anti-theft uses.
Polysulfide Adhesives
Polysulfides were initially used as sealants and have significant applications in sealing double-glazed mirror edges. Both are used to hold units together and create barriers against moisture intrusion. They are prepared using bis(2-chloroethyl) formal with sodium polysulfide and include mineral fillers to reduce costs. Plasticizers, such as phthalates and silane coupling agents, are used, while their hardening agents include manganese dioxide and chromate.
Silicone Sealants (Aquarium Adhesive)
One-component silicone adhesives, often known as RTV adhesives, consist of polydimethylsiloxane (PDMS) with molecular weights ranging from 300 to 1600, featuring terminal groups like acetate, ketoxime, or ether. These groups are hydrolyzed by atmospheric moisture, forming hydroxyl groups that subsequently condense by removing water. Silicone adhesives are flexible and desirable, offering good environmental and chemical resistance. These adhesives are recognized as the best coatings for use in bathrooms. In the Iranian market, they are commonly known as aquarium adhesives. Due to their widespread applications, aquarium adhesives can be found in nearly all homes. Their main applications include:
Home Repair and Maintenance
The most common and popular use for silicone adhesive (aquarium adhesive) in repair, remodeling, and home construction projects is to fill and seal joints and cracks in sinks and bathrooms. Silicone adhesive is regularly used to fill holes and clean any cracks and gaps. It can also be used to seal surfaces like ceramic floors.
Sealing and Bonding Glass
Aquarium adhesive is an excellent sealant and bond that also has the capabilities of most common adhesives; it is flexible and durable with strong bonding properties that can be applied to almost any surface, including plastic, metal, and glass. One of the most common uses for silicone sealants is for bonding and securing mirrors in bathrooms.
Automobiles
Silicone sealants are used in various parts of vehicles. The most important role of silicone sealants in the automotive industry is protecting gaskets under high pressure and temperature in car engines, etc. (thermal silicone).
Building Glass Aquariums
Glass sheets can be easily bonded together using aquarium adhesive (silicone sealants) over large areas. Aquarium adhesive is highly resistant to water and high temperatures, providing a strong and long-lasting bond between glasses.
Wood Adhesives
Adhesives that cure upon solvent removal:
Contact Adhesives: Contact adhesives are among the most well-known types (shoe glue, iron glue, PVC glue) and are solvent-based. These are solutions of polymers in organic solvents applied to both surfaces to be bonded. The main substance in these adhesives is chloroprene rubber (polychloroprene, chlorobutadiene rubber) and is used to bond decorative laminates and other hard plastics like ABS, PVC to wood and metal products, as well as DIY contact adhesives for shoe soles.
General Purpose Paste Adhesives
Solvent-based adhesives sold in paste-like containers are often solutions of nitrile rubber (copolymer of butadiene and acrylonitrile) in organic solvents.
Tile Adhesives (Synthetic Latex Adhesive)
These adhesives fill gaps, making them suitable for securing suspended ceiling tiles made from polystyrene and for plaster and gypsum application. They can also be used for floor tiles. Like rubber resin adhesives, they allow for some movement without cracking.
Filler Adhesives (Polyurethane Foam Adhesives)
These adhesives are pressurized in spray cans, filling existing cavities in wood, etc., as the foam expands when sprayed. If you need to remove them, you must use a specific solvent.
Super Glue 123 (Cyanoacrylate)
These fast-acting adhesives bond various small household and industrial items, including metals, glass, ceramics, and plastics. However, be careful when using them as they can bond your skin to other materials, and if you accidentally glue items together, you will need special removers to separate them. Super glues in the Iranian market are sold as Glue 123 along with an activator spray.
PVC Glue (Pipe Glue)
These adhesives are used for sealing and bonding high-pressure PVC-U pipes. These adhesives dissolve a portion of the PVC pipe surface due to their specific solvent type and then create a cold weld-like bond within 8 to 24 hours.
