The primary difference between sealants and adhesives is their main goal or objective. Sealants are designed primarily to close gaps between surfaces, and to prevent things like dust, water, or debris from getting in to a given space. Adhesives, on the other hand, are generally made to permanently stick to surfaces together — not so that nothing can penetrate, but rather so that the surfaces can’t be separated. Sometimes sealants are used between two surfaces, but not always. In fact, it’s pretty common to see sealants placed on the exterior walls of buildings and appliances, but adhesives are almost never used this way. The products are often sold together and can sometimes be used interchangeably, but this isn’t usually recommended. Sealants don’t always have the sticking power needed for long-term adhesion, for instance, and adhesives won’t always dry properly when used on an exterior surface. Some manufacturers produce hybrid products that attempt to serve both purposes, but these won’t always work well for all projects.
General Purpose of Each
A sealant is a product that is mainly used in the finishing of products or at some other stage during the production process. Just like the name suggests, the main function and use of a sealant is to seal any space that exists between surfaces where they are applied in other to create a watertight or airtight area. The sealant may be utilized in any specified capacity where the intention is to keep something in, or just the opposite — to keep something out. For instance, the product could be utilized during various construction projects, where it can be applied in various capacities to fully seal openings between surfaces that may be difficult to close in any other manner. When used in home construction, a sealant can be applied to keep out air drafts, soot or any other minute particulate matter.
On the other hand, the adhesive’s main purpose is usually to bind one surface to another, not to seal the space in between objects. Adhesives bond things together, and work sort of like industrial glue. Sometimes this serves the dual purpose of sealing cracks or open spaces, but not necessarily, and not usually primarily.
Structural Basics
Sealants and adhesives also differ in their basic structure, look and feel, as well as their primary ingredients. In general, adhesives are more rigid and powerful than sealants, which are generally more malleable and don’t usually have as much strength. Sealants are usually made of polymers specifically calibrated for a tight molecular structure that doesn’t allow penetration. They also usually contain fast-drying resins and epoxies that form a slick finish.
Adhesives are usually filled with much more complex structures designed to grip and bind on a cellular level. They’re usually much longer lasting, and can often be all but impossible to remove. Most sealants, conversely, can usually be peeled or stripped away with just a bit of effort.
Preparation and Use
Another difference between sealants and adhesives can be seen in the type of preparation that goes into the application of the two products. For instance, since the function of an adhesive requires a better adhesion to the surfaces in order for it to hold properly, it’s usually really important for users to thoroughly clean and sometimes even treat the target area to make sure that the binding sets. Most adhesives come as sprays or paints. Sealants, on the other hand, still require a clean surface, but don’t usually need any special treatments in order to work. They are more commonly applied with a caulking gun or specialized applicator.
Combined or Hybrid Products
Even though an adhesive is not primarily meant for the purpose of providing an airtight area in the place where it is applied, depending on the type of material and its size, it may also serve as something of a substitute where the sealant is not available. Sometimes, in some circumstances, the two products can be used interchangeably. Some manufacturers also produce hybrid products that promise to be both a sealant and an adhesive in one. A lot depends on the exact production as well as the project at issue, but in most cases, hybrids aren’t as good as more “pure” products.
