1. Introduction to silicone sealant
Silicone sealant is also called silicone structural glue. It is a very important sealant for construction. It requires no heating, light, or other special conditions. It can solidify into elastic material at room temperature. Silicone sealants are silicone products. It has strong adhesive properties and high tensile strength. It is also weather-resistant, vibration-resistant, moisture-proof, and can adapt to temperature changes. It is also very convenient to use. Due to its versatility, it has important applications. It is often used to bond various building materials. Silicone sealants can fill gaps between structural elements and bond materials. It reacts with moisture in the air at room temperature. It then cures into elastic silicone rubber. So it is also often called “room temperature glue”.
2. Classification and Applications
Silicone sealants can be divided into structural sealants and general sealants.
Structural adhesives in construction projects have long had strict requirements. These adhesives are essential for bonding building materials to major structural elements. For example, in glass curtain wall applications, the material must be able to withstand wind loads and the self-weight of the glass. It must also meet the specified elastic modulus standards. So it requires a high technical content.
As living standards improve. Sealants containing anti-mildew and antibacterial ingredients are increasingly favored by consumers. Depending on the chemical properties of the material, sealants are available in the deacidification type, dealcohol type, deketoxime type, etc.
- 1. Deacidification type (acid sealant). It is most commonly used due to its fast curing speed and high bonding strength. It is suitable for sealing, plugging, leak-proof, weatherproofing, and other occasions. But during curing, it produces acetic acid. It will cause certain corrosion to metal materials.
- 2. Dealcohol type (neutral sealant). It avoids the generation of acidic substances during the curing process. Although its adhesion is strong, it has the disadvantage of a relatively slow curing speed.
- 3. Deketoxime type. Used as a structural adhesive, such as the structural bonding and sealing fields of glass curtain walls and insulating glass.
3. Product Performance
In comparison to other materials, key performance factors of organic silicon products include:
3.1 Temperature resistance
The usage temperature range is extensive. The main chain structure of silicone products is silicon-oxygen bonds. The silicon-oxygen bond energy is 121 kcal/gram molecule. In contrast, carbon-carbon bonds have a bond energy of 82.6 kcal/mol. So, silicone products have high thermal stability. Molecular chemical bonds do not break or decompose at high temperatures. Additionally, they exhibit excellent low-temperature resistance, surpassing that of other materials.
3.2 Weather Resistance
Extended service life is a hallmark of silicone products. Ozone in the atmosphere is most destructive to polymer materials. It can cause oxidative degradation and thus lose its use value. Especially rubber materials contain double bonds. The main chain structure of silicone products is silicon-oxygen bonds. And there are no double bonds. So, it is not easily decomposed by ultraviolet rays and ozone. They can last for decades in the natural environment.
3.3 Electrical Insulation Performance
Compared to most insulation materials. Silicone products exhibit excellent dielectric loss and withstand voltage and surface resistivity. They serve as stable electrical insulation materials in the electronics and electrical industries.
Silicone sealant has excellent weather resistance and anti-aging properties. It is particularly beneficial for applications that require long-term exposure to outdoor environments, such as curtain walls, photovoltaics, etc.
In the field of building curtain walls, silicone glue is usually used in two scenarios. 1. The only connection between the curtain wall glass and the backing aluminum alloy frame, and the transfer of loads. 2. As a hidden frame glass curtain wall joint seal to resist wind and rain intrusion. Although the design life of glass curtain walls is generally 25-30 years. However structural adhesives and sealants tend to have shorter warranties. Some inferior sealants may cause problems within 1-2 years. It will cause the glass to fall off and cause serious safety accidents. It can be seen that the field of building curtain walls has higher quality requirements for sealants.
In an insulated glass field, an insulated glass sealant system must use double sealing. It uses the first coat of sealant to protect against water vapor. It uses a second layer of glass sealant to maintain structural stability. Among them, the first glue is mostly made of butyl glue, and the second glue is mostly made of organic silica gel.
4. Supply and Demand Landscape
At present, China’s normal temperature glue consumption is about 1 million tons. The industry market size is approximately 30 billion yuan. Among them, the consumption of silicone sealants for construction accounts for about 58%. The largest consumer area of silicone sealants in the world is the construction industry. In the United States, Japan, and Europe. The consumption of normal temperature adhesives in construction accounts for 44%, 38%, and 40% of the total consumption in these areas respectively.
The widespread use of silicone sealants in China began in the 1980s. Acidic silicone sealant is currently the most commonly used variety, especially in the field of construction. China’s rapid urbanization process promotes the rapid development of glass curtain walls, aluminum curtain walls, and stone curtain wall materials. So, the requirements for bonding and sealing materials are also corresponding increasing. This promotes the large-scale application of sealants.
At present, the annual production capacity of China’s silicone sealant industry exceeds 1.5 million tons/year. The output is approximately 1.04 million tons. The annual export scale is about 50,000 tons. The import scale is less than 10,000 tons.
5. packaging Methods
According to the packaging method, it can be divided into single-component (RTV-1) and two-component (RTV-2). One-component silicone structural sealant, mainly used for small curtain walls and on-site construction. Two-component silicone structural sealant is mainly used in large-scale curtain wall construction.
Silicone glue is resistant to high and low temperatures, weather aging, and ozone. It has good adhesion to various substrates and has strong resistance to displacement. Therefore, it is the only structural bonding sealing material for hidden frame curtain walls. Silicone sealants not only completely isolate and seal the inside from the outside. It can also securely bond decorative panels such as glass to metal frames on buildings. Since the glass panels have no other mechanical fixings. Silicone structural sealant itself has good elastic deformation ability. It creates a resilient connection between the main body of the building and the decorative glass panels. This can reduce losses caused by natural disasters such as earthquakes and hurricanes. Therefore, the quality and use of silicone structural sealant play a decisive role in the safety of hidden frame glass curtain walls.
