What Is a Metallic Adhesive?
Metallic adhesives are adhesives that can bond on metal surfaces.
Adhesives for metals include those that can bond between metals such as stainless steel, iron, and aluminum, as well as those that can bond between metals and non-metallic materials (e.g., plastic, wood, ceramics, and carbon fiber). Many products have excellent heat resistance, water resistance, and impact resistance.
Uses of Metallic Adhesives
Metallic Adhesives are used in a wide range of applications, whether for household, industrial, or architectural use. Metals that can be bonded include stainless steel, titanium, aluminum, iron, galvanized steel, copper, brass, and many others. Other non-metallic materials that can be bonded to metals include plastics, wood, glass, ceramics, carbon fiber, and many others.
1. Household Use
Household metal adhesives are used in applications such as DIY furniture, repair of kitchen, bathroom, and other water-related items, cord repair for digital equipment, car body and muffler repair, water pipe repair, and fence repair. It is also possible to repair eyeglass frames and accessories such as necklaces. Other applications include handmade accessories, gluing and repairing model trains, and repairing fishing tackle such as lures.
2. Industrial Applications
In industrial applications, metal adhesives are used as an alternative welding method to mechanical fastening and welding. Typical applications include bonding metal parts such as electronic components, heaters such as wire thermocouples, sensors, and other building materials and structures.
Principle of Metallic Adhesives
Metallic Adhesives, like general adhesives, bond by adhesive force and cohesion. Adhesion is the force that binds different molecules together, while cohesion is the force that holds the same type of molecules together. Adhesives are effective when they adhere to the surface of an object in liquid form as a liquid substance and cure. Curing is caused by polymerization, chemical reactions with curing agents, and evaporation of solvents.
There are several types of adhesives that can be used for metals, and each type has a different adhesion mechanism. The adhesion strength of adhesives is usually due to physical (mechanical) bonding, chemical bonding, or dispersion bonding.
1. Epoxy Resin-Based Adhesives
Epoxy resin-based adhesives are one type of adhesives that can be used on metals, and are available in one- and two-component types. Generally, the two-component type is the most common, in which adhesion proceeds through a chemical reaction caused by mixing two liquids. Compared to ordinary adhesives, this type of adhesive has the characteristic that its volume does not decrease easily when it cures. Other than metals, it can be widely used for bonding to wood, ceramics, glass, etc., and can also be used for bonding to non-metals. These adhesives have particularly excellent properties in terms of durability, heat resistance, and water resistance.
2. Elastic Adhesives
Elastic adhesives are adhesives that remain soft even after curing and have rubber-like elasticity. They are particularly suitable for bonding materials that are made of different materials. However, it cannot be used for bonding metals.
When bonding different materials, cracking, warping, or peeling may occur over time due to differences in the coefficient of thermal expansion. The coefficient of thermal expansion is a value that indicates the rate at which the length and volume of an object expands as the temperature rises. Elastic adhesives are less likely to crack, warp, or peel because the adhesive becomes elastic and rubber-like after curing. Also, since the adhesive layer absorbs shock, it is often relatively resistant to impact and vibration.
Types of Metallic Adhesives
Metallic Adhesives can be broadly divided into those for household and commercial use. Different products have different characteristics such as thermal conductivity, electrical conductivity, heat resistance, and UV resistance, and should be used according to the intended use. In addition, some types of metal adhesives can bond metals and non-metals, but not metals to metals, so care must be taken.
1. Household Use
For household use, instant adhesives for metals, epoxy resin-based adhesives, and elastic adhesives are used. Instant adhesives for metals are instant adhesives with high adhesive strength to metal surfaces. Instant adhesives cure by chemical reaction, so they can bond instantly without waiting for time to dry. The main reaction proceeds with moisture in the air or on the surface of the substance to be bonded.
Among various metal adhesives, the time to dry, capacity, impact resistance, water resistance, heat resistance, and UV resistance vary depending on the product. It is necessary to select the appropriate one for the application. For example, a quick-drying adhesive that cures in a short time is suitable when the range of use is narrow, such as for bonding metal fittings of accessories or repairing various small parts. On the other hand, if the area of use is large, such as repairing houses, cars, motorcycles, etc., a long curing time will be easier to work with. The longer the time to cure, the easier it is to make corrections after application.
Impact-resistant types are appropriate for areas subject to loads and impacts such as joints, while heat resistance is required for electronic equipment and areas around car engines. Water-resistant adhesives are required for use in kitchens, bathrooms, and other watery areas. For crafts and handicrafts such as accessory making, adhesives with a transparent finish can be used to keep the adhesive from being visible and to maintain its aesthetic appeal. In addition, since adhesives may stick to the container if stored for a long period of time, it is appropriate to select a small volume product if the amount or frequency of use is small.
2. Commercial Use
Metallic adhesives for professional use are alternatives to welding, screws, etc. Specific types include epoxy resin adhesives, acrylic resin adhesives, hot-melt adhesives, and light-curing adhesives. Curing time, dischargeability, workability, impact resistance, water resistance, heat resistance, and electrical conductivity vary depending on the product, so it is necessary to select the right one for the application.