Structural Sealant

Structural Sealant is a two-component neutral-curing silicone sealant that offers excellent unprimed adhesion to many substrates. It is also highly resistant to weather.

In the present study, small-scale system specimens were exposed to combined mechanical and climatic loading at regular intervals for a total of 50 durability cycles. These durability cycles were designed to represent one year of service exposure.

Durability

Structural silicone sealants are moisture curing polymers that take in the surrounding moisture to polymerize into a tough, flexible, and temperature resisting rubber compound. This type of sealant can be used for many applications including insulating glass facades, structural glazing, and other high performance glazing systems.

During the design stage of a structural glazing system, durability and long-term service life should be considered. Durability is a critical factor in choosing the correct materials for a system. The ability of a structural silicone sealant to retain its original properties and perform well after exposure to a variety of different climatic conditions is important for ensuring a durable, effective, and safe glazing system.

To assess durability, laboratory tests can be conducted to determine the mechanical characteristics of a structural sealant after combined exposure to climatic and mechanical loading. The results of these tests can be compared to the behavior of the sealant Structural Sealant in the field and help to determine the durability of the bond.

Durability testing is usually conducted in two series, each consisting of a sealant that is subjected to a combination of mechanical and weathering load cycles. Each test series involves a mechanical loading device with actuators, which are arranged inside a climate cabinet, and an extra specimen that is positioned in a weathering rack next to the mechanical loading device.

The mechanical properties of the structural sealant can be evaluated by monitoring a number of dynamic mechanical parameters such as swelling dynamically induced force paths (extension/ compression, shear) over multiple climatic seasons, dissipated energy, and shore A hardness. The latter is a measure of the ability of the sealant to absorb and damp mechanical stress throughout the exposure period.

As can be seen in Table 2, despite 23+2 years of natural aging, the structural sealant passes all key initial mechanical strength criteria and residual tensile strength requirements, according to European ETAG002-1. The strong tensile and shear strength values achieved by this sealant are also an indication of its ability to maintain its original characteristics during accelerated aging and provide a high level of safety in use.

Adhesion

Adhesion, or the ability of a sealant to stick to various substrate materials is important for sealing and waterproofing building construction joints. Each specific type of sealant has different adhesion characteristics and will vary with the material it is intended to adhere to.

In general, a sealant should adhere to the substrate well and will not stain or degrade the surrounding materials. The sealant should also not be affected by the climatic conditions of the area where it will be installed. The manufacturer should provide laboratory test results to verify the product’s compatibility with the substrate.

Generally speaking, adhesion values are determined by the sealant’s modulus. A stiff, high-modulus sealant will have a higher adhesion value than a lower-modulus, softer product. A low-modulus, ultra-low sealant will have a low adhesion value but may have the ability to expand with little or no force.

The proper adhesion force depends on the application and the need for strength. A higher-modulus sealant is generally desired in traffic areas and in most cases will be needed for a structural application. A low-modulus, softer product will be used where elasticity is important.

One way to determine the proper adhesion force is to run the C920 adhesive movement test. This is the most rigorous test that can be performed on a sealant. This test will give a manufacturer a very good idea of how well the sealant will perform in the field.

Another important thing to note is that there are many different test methods and limits within the C920 specification. This is very important to understand as this is a very detailed specification and is very difficult for a sealant to pass.

As an example, ASTM C719 is one of the most commonly used test methods. This test tests the sealant’s ability to handle a joint with some movement for an extended period of time.

In this test the sealant is embedded in a strip of stainless steel or aluminum screen. This strip is then placed on a standard concrete surface. It is then cured and the test is conducted. The test results are then compared to the manufacturer’s data sheet and any differences are noted.

Adhesive Strength

The adhesive strength of a sealant is very important in ensuring that the joint is sealed. It needs to be strong enough to bond securely and continuously to the substrate, and it also needs to be able to handle the movement of the joints under field conditions.

There are a few tests that can be done on the job site to test for adhesion (some are more simple than others). One is ASTM C794 which has a strip of sealant adhered to a standard concrete substrate and then cured. It is then partially undercut to make a tab that a worker pulls by hand. This test is simple and most manufacturers use it to determine if a sealant can be used on certain types of substrates.

If a sealant fails this test it is unlikely that it will pass the C920 specification. It needs to demonstrate no more than 25% adhesive bond loss and the adhesive strength must be at least 22.2 Newtons. This is a minimum value but it does not consider the stiffness of the sealant and it may not be sufficient for a stiffer product.

Adhesion testing is a good way to determine if a particular sealant will work for the job at hand but there are exceptions to every rule. For instance, if the substrate has a lower modulus than the sealant then you can get away with a lower adhesion value since it does not require as much force to be applied to the bond line.

However, if the sealant has a higher modulus then you have to have a very high adhesive value in order to make sure that the joint can be maintained during joint movement and not experience adhesive or cohesive failure. This is why the ASTM C920 peel test is important because it has a very specific mode of failure that is necessary for the sealant to be qualified to this specification.

If a sealant passes the ASTM C920 test and also has an adhesive strength of at least 22.2 N then it is likely that it will be able to meet the requirements of this specification for major projects. It will need to demonstrate that it can maintain its adhesive strength over a long period of time under field conditions and not lose more than 25% of the bond strength.

Weather Resistance

Structural sealant is a type of structural adhesive which can be used for building joint bonding. It can be used in a wide variety of applications such as the bonding of steel, carbon fiber, wood, and other materials. It can also be used for the repair and reinforcement of cracks in the structure.

The weather resistance of a sealant is determined by the amount of sunlight, water, and chemicals that it encounters. It is important that the sealant can withstand these exposures without failing.

Many sealants are designed for use in a wide range of different applications, such as window and door production, curtainwall construction, etc. They offer a combination of mechanical properties, high ultimate tensile strength, un-primed adhesion to most building substrates, and excellent weather-ability.

For example, Dow’s Structural silicone is an excellent choice for bonding glass or metal to the Structural Sealant structure of a building. It has a high level of resistance to UV, is highly resistant to weathering, and can withstand a variety of temperatures.

In addition, it is a highly versatile sealant that can be applied to a variety of different surfaces, such as glass, stone, and metal. It can be cured quickly and is easy to apply.

While structural adhesive is able to withstand a certain degree of tensile and shear force, it may not be able to resist alternating forces such as wind or rain for very long periods of time. Therefore, it should not be exposed to the elements for an extended period of time.

Another important consideration is the ability of the sealant to withstand joint movement. The joint-movement capability of the sealant can be determined through an ASTM C-719 test method.

The test method is intended to determine the maximum expansion and contraction (stretching and compressing) that the sealant can perform over the life of the joint. This varies depending on the sealant’s modulus and is dependent on the expected movement of the joint.

A low-modulus sealant has the ability to expand by up to 100 percent of its original width and a medium-modulus sealant can perform up to 50 percent of its original width. Often, these sealants are used in EIFS and composite cladding systems where high stress can be experienced by the joint during its life.