Structural sealants are used to fill gaps between two or more substrates while providing excellent adhesion to a variety of materials. They also prevent the loss of pressure or liquids and protect components from condensation and corrosion.
A wide range of applications for sealants exist and a variety of polymer chemistry types can be available to meet specific needs. It is important to choose the correct type for your application.
What is a Sealant?
Structural Sealant is a type of silicone adhesive that is primarily used in the construction industry to bond metal, glass, and ceramic panels together. It also has excellent weather-resistant properties and is resistant to heat, cold, and harsh elements.
A structural sealant is used for the transfer of external and internal loads, which helps to ensure that structures stay intact. It is typically used for curtain walls, doors and windows, airport runways, highways and bridges, and engineering joints.
It is also used to prevent water from entering building joints and is a common method of waterproofing. The application of a structural silicone sealant in conjunction with an air-tight membrane prevents water from entering the joint and compromising its integrity.
There are two main types of structural silicone sealant: one-component and two-component. The one-component type is a one-step, self-priming, shelf stable, neutral-cured elastomeric adhesive that exhibits superior Structural Sealant unprimed adhesion to most common building substrates such as glass, reflective glass, anodized aluminum, granite, and most paints.
The two-component type of structural silicone sealant is a more complicated process that requires mixing and blending of both components in order to achieve full cure. It may take several hours to reach full cure, so it is best used in situations where the application is likely to be prolonged and extensive.
As the name suggests, a structural silicone sealant is made from a rubber compound that has been modified with an elastomeric additive that adds elasticity to the sealant and enhances its strength. The elastomeric additive also improves its resistance to bending and provides it with additional impact resistance.
A structural silicone sealant is used in the assembly, installation, and repair of curtain walls and insulating glass. It is a highly effective and economical means of sealing between the glass and its perimeter support system and retaining the glass in the opening.
This type of sealant is a very durable, non-toxic, and non-polluting product that is often used in high-rise buildings. It is also commonly used in the manufacture of walk-in refrigerators and showcases for restaurants, food-safe areas on cruise ships, airplanes, and trains.
Sealants are a key component of a building’s structure. They are used for a variety of purposes such as to bridge gaps and create joints between different parts, to bind different elements together, and to protect against water and air infiltration. The design and use of these joints can have a significant impact on the performance of a building and its components.
There are a wide range of sealant products available and they are categorised by their chemical composition, form, application and durability. Some are polymers that set by drying (such as acrylic, or rubber/solvent-based sealants) and others are elastomeric compounds that have a degree of flexibility which allows the joints to move whilst still providing a strong bond between them.
The elastomeric compounds are usually plastic or rubber but some are based on silicones, which are more durable and have a higher resistance to weathering. These are generally used for high-performance applications such as in the construction industry.
These sealants are usually supplied in cartridges which can be extruded on-site, or as preformed sealants such as dry tapes, ribbons, or extruded shapes. Some are available in a hot-melt form.
One-part systems are often used for on-site application, but in some cases two-part systems are preferred as they offer a wider range of colours and can be stored up to 12 months without a problem. The mixed paste can then be pumped or dipped in the joint.
In contrast, the older oleoresinous and rubber/solvent-based sealants are more difficult to apply on-site and they have a limited pot life. They will start curing after about 30 to 60 minutes, but it will take a much longer time before the entire joint is completely cured.
Some of these can be applied using a gun, which includes PVC made cartridges with nozzles. The gun can be used to apply a single sealant in any position, or a mixer is required for two-part system sealants.
The tensile and shear moduli decrease significantly during the combined mechanical and weather cycling, but these are not at the same level as those of the specimens that were not exposed to both climatic and mechanical loading. As the dynamic stress relaxation of the filled silicone elastomers is mainly determined by the previous load combinations, this effect is influenced by ambient conditions.
Structural sealants are a vital component of building design and construction. They are used to seal joints and openings (gaps) between substrates such as glass, window frames, or stone. The sealing of the gap prevents air, moisture, and other environmental elements from entering or exiting a structure while permitting limited movement of the substrates.
The most common applications of structural sealants are in commercial and residential buildings. They are also used in industrial applications and other specialty applications such as fire stops or electrical or thermal insulation.
There are many different types of sealants and their performance can vary according to the application, the materials of construction of the joint, and the other materials that will be in contact with the sealant. These factors must all be considered.
Adhesion Properties: A sealant’s ability to stick to the various substrates is critical to its performance. Early adhesion failure can result in a reduction in the sealing capability of the sealant. This can be mitigated by the use of primers that promote bonding to the substrates.
Cohesive Properties: A sealant’s strength to, “hold itself together” is equally important as its adhesive ability. This strength enables it to resist the tensile and shear forces that occur when the material is subjected to stress during installation.
Durability Properties: Sealant durability is the preservation of its performance to the specific substrate(s) over a designated service life. This includes the resistance of the sealant to environmental strains such as ultra-violet radiation, moisture, temperature, cyclic joint movement, movement during curing, and biodegradation.
Tests & Standards: There are many tests that can be conducted to determine the performance of a structural sealant in a particular application and the durability it will have to resist the effects of weathering over time. Some of these include:
Initial Mechanical Strength Tests: These tests evaluate the elasticity of the sealant when it is subjected to tensile or shear forces acting on a joint at different temperatures. Temperature-induced variations in the sealant’s elasticity can cause a drop in tensile and shear strength values. The resulting reduction in these values may result in the deterioration of the sealant’s adhesion and cohesive properties.
Sealant maintenance is an important component of a building’s overall structural integrity. It is the first line of defense against water intrusion and helps to extend the service life of your structure and its investment.
A thorough annual inspection program can significantly prolong the lifespan of joint sealants Structural Sealant and prevent structural damage caused by a range of environmental conditions. A robust plan that includes joint inspection, patching/resealing surfaces, power washing, and replacement of failed sealants can help to protect your structure’s investment and improve its value.
One of the most significant factors influencing structural integrity is the weather. The temperature and moisture content of the air in a building can impact the quality of your sealants and the longevity of your structure’s protection.
As a result, it is vital that all sealants be tested for their ability to withstand the various elements of a building’s climate. This testing can be done in a variety of ways and should be based on the knowledge of the specifier, architect, or applicator.
The main factor that influences longevity of a sealant is how well it resists movement and exposure to water, temperature, and chemicals in the environment. There are a number of tests that are available to determine the ability of a sealant to withstand these elements, but these can be complex and time-consuming.
For example, ASTM C1589 10B and 10C are outdoor studies that expose the sealant to a wide variety of climates and temperatures to test its durability. Several manufacturers are also doing this type of testing to assess the longevity of their products in different regions and conditions.
In addition, the performance of a sealant can be measured through tensile and shear testing. The results of these tests reveal the strength and damping capacity of a sealant. However, these results do not reflect the actual strength and durability of the material. In fact, some sealants can fail after only a few years of exposure to harsh weather conditions. In this case, it is necessary to replace the sealant and begin a new durability evaluation.