What Is Structural Sealant?
Structural Sealant is a moisture curing polymer that takes in the surrounding humidity to polymerize and form a tough, flexible and temperature resisting rubber compound. These are the polymeric sealants that can be found in a number of building applications, such as glass, metal and curtain wall production.
While structural silicone sealants are widely used in curtain wall assembly, installation and repair work, the durability of this adhesive is often overlooked. This is particularly true in Europe where there is no clear guidance on the long-term performance of SSG structures.
Sealant Selection
When it comes to choosing the right sealant for a specific application, there are many things to consider. For example, the chemistry of the polymer used is important as it can influence a number of properties including adhesion and durability. Additionally, the type of application and the substrates that will be bonded can determine what polymer is most suitable for the job.
Ultimately, the most important consideration is what sealant will best perform in the particular application. There are several factors that can affect this, including moisture, temperature, cyclic joint movement, and movement during curing.
In addition, the adhesive bonding strength and cohesion of the sealant can significantly impact its performance over the life of the project. This is why it is important to ensure that the sealant will be able to pass a test to verify its performance over time.
There are several different tests to evaluate the ability of a sealant to move in a joint. One of the most common is ASTM C719 which is validated by the SWR Institute (SWR Institute Product Validation Program).
This test requires the joint to be exposed to accelerated artificial weathering for only 100 hours. It is the most rigorous test that can be done to determine if a sealant can handle a given level of movement over the course of its useful life in a specific climate and application.
The other most commonly used test is ASTM C510 which uses a standard concrete as the substrate and exposes the joint to accelerated artificial weathering for 20 days. It is the most popular test to use for structural glazing, but also applies to other types of architectural applications like glass, window frames and stone.
Both of these tests are very good and provide a clear understanding of what a sealant can handle during its life span. However, it is also important to understand that these tests only test the initial performance of a sealant and does not predict how it will perform in the field.
This is why it is so important to consult with the sealant manufacturer to ensure that it will perform in the specified environment. The sealant manufacturer can help the specifier select the right sealant for their application and will have available a range of data to show the performance of their product.
Adhesion
Adhesion is a term used to describe the attraction of two substances together. The word adhesion is derived from the Greek root words ad (to) and hesion (to stick to).
There are a number of different mechanisms that are associated with adhesion. These include adsorption, mechanical interlocking, interdiffusion, and surface reaction. The first mechanism is adsorption, which occurs when adhesive molecules adsorb onto an adherend surface and bond with it.
The second mechanism is mechanical interlocking, which occurs when the adhesive molecules flow into pores or around projections on the adherend surface. The third mechanism is interdiffusion, which occurs when the liquid adhesive dissolves and diffuses into the adherend material. The fourth mechanism is surface reaction, which occurs when the adhesive molecules chemically react with the surface of the adherend material.
These mechanisms are the basis of adhesives’ ability to adhere to their surfaces. However, there are many other factors that determine the amount of adhesive an adhesive can have on a given surface.
For example, the properties of Structural Sealant an adhesive surface can be affected by environmental factors such as temperature and humidity. This affects the strength of the bond between the sealant and the substrate and its ability to withstand external forces.
This is important when deciding on the type of sealant to use. For example, a structural sealant must have sufficient mechanical and bonding strength to withstand tensile stresses while a weather resistant sealant needs to be strong enough to withstand abrasion.
Another important factor that can affect the adhesion of a sealant is the substrate’s surface texture. This is especially true for substrates such as stone, mortar, and aluminum. If the substrate is too rough, it can reduce the effectiveness of the adhesive, and if it is too smooth, the sealant may fail.
Regardless of the specific surface texture, it is always important to ensure that the sealant will adhere to the substrate in a manner that is consistent with the specifications and recommendations of the manufacturer. For example, if the data sheet says that the adhesive is generally unprimed, then you should ask the manufacturer to test the product on job site substrates that are close to the substrates that will be applied to the project.
Durability
Structural sealants are moisture curing polymers that will take in the surrounding moisture and polymerize to create a tough, flexible and temperature resistant rubber compound. These are ideal for bonding and sealing structural glazing to a variety of Structural Sealant building substrates such as glass, metals, ceramics and composite materials, providing a durable and water-tight seal.
Several different types of structural sealants are available for use in the construction industry including silicone, urethane, acrylate and acrylics. Each of these is designed to meet specific needs for a variety of applications, including structural glazing, curtain wall and roof systems.
Silicone structural sealants are a type of moisture curing polymer that will take in the surrounding humidity to polymerize and form a tough, flexible and temperature resistant rubber substance. These are a popular choice for sealing and bonding structural glazing to a variety of building substrates including glass, metals, ceramics and composites.
Unlike many other adhesives that can lose their strength in response to natural aging, silicone structural sealants continue to display their original mechanical properties throughout the entire life of the product. This is especially noticeable with accelerated weathering tests such as those conducted in ASTM C734 where the cured sealant is cooled to 0 degF (-17degC) or 32 degF (-20degC) and quickly bent over a mandrel.
In addition, tensile and shear tests were carried out at various temperatures and the corresponding residual strength ratios were calculated. The tensile and shear strength values were then evaluated against ETAG002-1 requirements for Initial Mechanical Strength and Residual Mechanical Strength.
The results clearly show that the 2nd generation of Dow Corning 993, a neutral curing structural 2-part silicone, passes both these key criteria with flying colors. Even after 23+2 years of natural aging, the resulting tensile and shear strengths still matched or exceeded the tensile and shear requirements for the ETAG002-1 initial mechanical strength test.
Additionally, the tensile and shear strength values of the naturally aged product also matched or exceeded the tensile strength requirements for the accelerated weathering test in ASTM C734. The resulting interfacial (adhesion) failure was minimal with a few points exhibiting significant loss of adhesion at the specimen corners.
Sustainability
Using sealant that is environmentally friendly is a key part of any building owner’s sustainability program. This can range from simple initiatives like minimizing the amount of materials that end up in landfills to more involved efforts that include reducing the number of volatile organic compounds (VOCs) in products and applying green building standards during construction.
In a general sense, sustainability means the ability of an organization to meet its financial goals and ethical obligations without negatively impacting the environment, community or society. It can also help organizations attract employees, customers and shareholders who share the same values.
The UN has established 17 Sustainable Development Goals (SDGs) that are aimed at achieving various objectives, including reducing poverty and hunger, improving health, education and living conditions, environmental sustainability and gender equality. These goals are designed to guide global discussions on how the world can best work together to meet environmental needs while ensuring a fair distribution of resources.
These SDGs are not intended to replace the current economic system; rather, they are a new way to measure progress and encourage new ideas and strategies to flourish while staying realistic about the future of our planet. They bring together a broad range of people with diverse skills and thought processes to talk about key issues.
According to the United Nations, economic sustainability is a process that combines conservation of natural resources and maintaining the quality of life on earth. It involves balancing expenses and revenues to earn profit in the long run. This principle applies to any economic activity, whether it is public or private.
Some examples of economic sustainability may include anti-poaching campaigns, nonprofit work or eco-tourism generating revenue from wilderness safaris and wildlife viewing excursions. The concept of sustainability has been formulated into a series of principles and is informally known as the Triple Bottom Line.
This approach to business has many benefits. It improves environmental quality, reduces waste and creates a more stable business model in the long term. Moreover, it can increase business revenues and attract investors who share these goals. It can also protect a company’s brand and mitigate risk.
