What Are Structural Sealants, and How Do They Work?

Sealants have been used for as long as people have been building things. Early sealants were made of mud and used to seal houses. Pine tar was used to make the seams in wooden boats watertight. Today’s sealants are manufactured for specialized applications in manufacturing, construction, and repair applications. Still, they serve the same primary purpose: to seal holes and gaps and create a watertight or airtight seal.

Sealants are made of different chemicals and compounds for various purposes, but all sealants fall into two basic categories:

1. Weather sealants are weather-resistant and used for waterproofing to create a seal that resists ultraviolet rays and weather exposure.
2. Structural sealants are heavy-duty adhesives used in construction and for critical applications.

What Is Structural Sealant?

You typically find structural sealants used for critical applications where high performance is desired, such as sealing load-bearing glass, secure window frames, mount stones, etc. Structural sealants are typically used to support construction anchors, reinforce cracks, fill holes, and other similar uses. Structural sealants come in one-component compounds and two-component compounds, such as epoxy, which must be mixed to activate.

Don’t confuse sealants with caulking materials—although sealants can be used that way. Sealants are designed to create a lasting bond between surfaces.

Advantages of Structural Sealants

Industrial sealants are often preferred over other types of fasteners for several reasons.

First, structural sealants are invisible and leave a clean, smooth joint. They adhere over a larger area to create a better bond and distribute the joint’s load. Structural sealants also absorb stress better than fasteners, which can offer a single point of failure.

Structural sealants also have the advantage of accommodating thermal expansion between different materials. They can be fast to install and are cost-effective. They also offer weatherproofing since they keep out moisture, resist UV rays, and can handle extreme temperatures.

Types of Structural Sealants

There are several types of structural sealants. Many of them are used for both residential and commercial applications.

Epoxy

Epoxy is available in any hardware store. This two-component sealant requires mixing a resin and a hardening agent. Once the epoxy has set and cured, it forms a strong, medium-hard bond that resists vibration. Epoxy is favored for its high thermal and chemical resistance.

Acrylate

Acrylate structural adhesives also require mixing two compounds, including a curing agent, for faster drying times. Acrylic adhesives are strong and versatile and are used to bond PVC materials, nylon, glass, cement, ceramics, wood, and other materials.

Silicone

Silicone sealants provide a strong bond and resist chemicals, moisture, and weathering. They also perform well in high temperatures and are oil- and UV-resistant. Many silicone sealants are used in manufacturing to bind plastics, metal, and glass. For example, windows are often sealed using silicone adhesive, and it’s used to make aquariums and plastic tanks.

Polyurethane

Polyurethane sealants are made from organic polymers, which can be adjusted for strength, hardness, adhesion, and other properties. Polyurethane sealants are used for sealing and bonding and can be applied to auto glass, metal structures, HVAC systems, and more.

MS Polymer

MS polymer sealants are a hybrid of silicone and polyurethane. They are easy to use, require little or no surface preparation, are environmentally friendly, and deliver a strong bond for general applications.

Applications for Structural Sealants

What are structural sealants used for? It is used in various construction applications.

Sealants replace fasteners and welding in frameless window glazing. Structural sealants are ideal for double- and triple-glazed windows.

Structural sealants also work well with concrete, bricks, or stone masonry. They are often used for expansion, shrinkage, separation, and slab floor joints.

You need structural sealants to join precast concrete slabs and panels. These panels tend to be small, so there is little movement, but if they cover a large surface, the cumulative effect could mean substantial shrinking and expansion. The best sealant for this is one with good adhesion to concrete, and elasticity is best.

Water can accumulate on both flat and peaked roofs, so you need roof sealants that repel water and are weatherproof. Roofs are made of different compounds, including shingles, tiles, concrete, and metal, so choose a sealant that works well with the materials and is waterproof.

Tile is usually sealed with cement grout, but sealing two large tiled areas requires a structural sealant. For example, in bathrooms, kitchens, and swimming pools, there is high humidity and a lot of water present, so you need a sealant to prevent moisture from seeping through the seams and ruining walls and subfloors.

Installing Structural Sealants

While structural sealants are made of different chemicals and compounds, the installation procedures are similar:

1. Start with a clean surface.

Properly cleaning the surface ensures the sealant can adhere properly. The surface should be free of dirt, grease, oil, or anything interfering with the bond. For glass, etch the surface. Use abrasion or etch the surface of the glass where it needs to accept the sealant. A roughened surface gives the adhesive something to grip. 

2. Prime the surface.

Primers promote a strong, consistent bond, especially with silicone sealants. Read the manufacturer’s instructions when applying primer. It’s essential not to use too much. Be sure the primer is dried before applying the sealant. 

3. Tape the area.

Consider using masking tape to outline the joint to ensure a neat seal. Be sure to remove the tape before the sealant cures.

4. Apply the sealant.

Once the surface has been prepped, you can apply the sealant. Every structural sealant application requires different procedures and tools to ensure a smooth seal. Follow the manufacturer’s instructions, and if you aren’t sure of the best approach, contact one of the experts at Bay Supply for advice. 

5. Let it cure.

Industrial sealants require adequate curing time, which depends on the type of sealant. Be sure to follow the manufacturer’s instructions.

The most common mistakes people make when applying sealants are inadequately preparing the surface, choosing the wrong sealant, incorrectly applying the sealant, and not letting it cure properly. To get maximum performance from any sealant, inspect the joint regularly for wear or cracking and clean and maintain the joint as needed.

Shop for Structural Sealants on the Bay Supply Marketplace

Structural sealants are a versatile alternative to hardware fasteners and offer several advantages. They can evenly distribute the joint load and provide an invisible bond for a neat installation. 

Visit the Bay Supply Marketplace to shop for the right structural sealant for your needs.