Structural Sealant
Structural Sealant
Structural Sealant is a high-strength adhesive that can accommodate movement within a joint. It comes in a variety of Liquid Applied Sealants. They are categorized into different movement classes and grades depending on their capability to accommodate movement.
A recently developed performance-based test method explores mechanical behavior and sealant response under superimposed climatic load over the course of an annual cycle. It also tests for adhesive and cohesive failure.
Durability
Structural Sealant is a high-performance silicone adhesive for structural bonding of glass, stone, and metal. It has high compressive strength, steel-steel positive tensile bonding strength, and shear strength and is resistant to aging, fatigue, and corrosion. Its durability allows it to transfer large loads from glass panes to the supporting structure and also withstand movement at joints. It can be used in the construction of high-rise buildings and bridges.
To assess the durability of Structural Sealant, we Structural Sealant conducted a series of mechanical tests. The test results from tensile and shear tests show that the structural sealant passes ETAG 002-1 Initial Mechanical Strength and Residual Strength requirements. Furthermore, the tensile and shear tests showed that the silicone adhesive withstands a combination of weathering and enforced movement without any loss of adhesion or failure of the bond.
The continuous characterisation of the system response during combined mechanical and climatic exposure was complemented by discontinuous characterisation, including visual inspection of the sealant joints as well as hardness measurements on the exposed surface of the sealant. It was observed that the stiffer sealant of series A has a higher hardness than the less-stiff sealant of series B. This is likely to be due to the stress relaxation behaviour of the two different structural sealants. It also reflects that the shear moduli Gdyn of the sealant of series A is higher than the tensile moduli EDyn.
Weather-Resistant
The most demanding applications for sealants are the ones on outside buildings. These joints must withstand movement as well as the harsh effects of sun, wind and rain. They must also be able to remain stable over a long period of time, without experiencing adhesive or cohesive failure.
The structural sealant is a load bearing adhesive and must transfer the external forces on the glass and glazing details to the curtain wall assembly; it is important for the structural sealant to have good tear resistance, elongation at break and tensile strength, as well as good durability. The weather resistant sealant is a non-load bearing adhesive and its main characteristic is resistance to the effects of UV radiation, snow and acid rain.
When choosing a sealant for the curtain walls of your building, ask about the ability of the product to handle the movement expected in the specific climate. You should also request data on how much dead load the sealant can carry, as well as the point at which it experiences either adhesive or cohesive (creep rupture) failure.
Structural silicones can be used to bond a variety of materials. The key consideration is to use the correct primer, and make sure the substrates are clean and dry. A wide joint is best, Structural Sealant as it can accommodate movement better, and a greater ratio of width to depth will allow the sealant to fill the gap. Use a joint backing or bond-breaker tape to eliminate “three-sided adhesion” and help the sealant flow into the gap.
Chemical Resistance
During the construction process the structural sealant must withstand many environmental factors. This includes exposure to UV radiation and rainwater. It should also be resistant to chemicals and solvents that may come into contact with the sealant.
It’s important to check the chemical resistance of the sealant prior to use by performing a compatibility test with the glass, metal frame and other materials that the sealant will be installed between. There are several industry tests that can be used to evaluate compatibility. A good option is the AAMA/FGIA 713 voluntary test for compatibility of sealants with self-adhered flexible flashings.
Another important consideration is the sealant’s ability to resist thermal shock, which can occur when the structure shifts between different temperature zones. This is why it’s important to perform a thermal cycling test. The test should include dynamically repeated tensile and shear testing at the onset of stress, then again after a period of time with enforced movement.
The test results should show that the structural sealant maintains its initial tensile and shear strength throughout a wide range of temperatures and under enforced movement. This is particularly important for ETAG 002-1, which requires that the mean residual tensile and shear strengths must not drop below 75% of the values measured after weathering and enforced movement.
Safety
Structural Sealant is a moisture curing polymer that takes in surrounding humidity to polymerize into an extremely tough, flexible and temperature resistant silicone rubber compound. This makes it an ideal adhesive for bonding, sealing and fixing applications in construction.
It is highly durable and will resist aging, fatigue and corrosion while remaining effective throughout its expected service life. Structural Sealant is an excellent choice for glazing, bonding and weatherproofing, especially in areas subject to vibration or movement.
When used as a structural sealant in curtain wall framing systems, it transfers all the structural loads from the glass panels to the metal framing system preventing potential glass pane collapse. It is also able to transfer wind load and other effects from the outside environment to prevent damage to the panel and frame structures.
The results of the initial mechanical strength tests on the structural sealant, performed according to ETAG 002-1 show that it significantly exceeds the required tensile and shear strengths for its intended application. It has a high initial mechanical strength and a good joint movement capability which is ideally suited for structural glazing tasks.
It is able to withstand the impact of flying debris, heavy traffic, blasting and earthquakes as well as extreme temperatures. It is also impervious to UV radiation, ozone, acid rain and fungus.
