Classification of Sealant Products in the Construction Industry 

Classification of Sealant Products in the Construction Industry 

In a secluded corner of a modern building, the sealant is protecting itself with its elastic form from the attacks of wind, temperature changes and displacement. Different types of sealant each perform their own duties, safeguarding the safety and durability of the building. 

Building sealants, as the "invisible guardians" of modern buildings, their performance directly affects the durability, safety and energy-saving effect of the buildings. Depending on the different base polymers, sealants can be classified into silicone type, polyurethane type, polysulfide type, modified silane polymer type and acrylic type, each type having its own unique performance characteristics and application scenarios. 

The global sealant market is continuing to grow. The market size of polyurethane sealants has reached approximately 20.7 billion yuan in 2023 and is expected to reach 26.7 billion yuan by 2030, with a compound annual growth rate of 4.2%. 

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01 Silicone sealant: Excellent weather resistance performance 

Silicone sealant is based on liquid silicone rubber of organic silicon oxide. It is one of the most widely used types of sealants at present. This type of sealant hardens when exposed to moisture in the air and releases low-molecular-weight products at the same time. 

Silicone sealants can be classified into acidic sealants and neutral sealants. Acidic sealants are prone to causing metal corrosion and concrete acidification, but they have good adhesion to glass; neutral sealants (such as alcohol-free type, ketoxime-free type, amine-free type, etc.) have a wider range of applications. 

This type of sealant possesses high-temperature stability, low-temperature flexibility, good elasticity, resistance to climate aging, water resistance, and is stable for glass bonding. The service life of high-quality structural assembly silicone can exceed 50 years, providing long-term security for building safety. 

Silicone sealant is widely used in the sealing of glass joints in curtain walls, joints in concrete buildings, and joints in stone materials. It is classified into multiple levels based on its displacement capacity and modulus to meet the requirements of different projects. 

02 Polyurethane Sealant: High Elasticity and Durability 

Polyurethane sealant is a polymer formed by the reaction of diisocyanates with polyether polyols. It is divided into two types: single-component and two-component. The single-component polyurethane sealant can be used directly and the construction is simple; the two-component one needs to be mixed in proportion before use. 

Polyurethane sealant has the characteristics of good wear resistance, high mechanical strength, excellent bonding performance, and good elasticity. It has excellent recoverability and can be used for dynamic joints. It has good low-temperature flexibility, excellent weather resistance, and a service life of up to 15 to 20 years. 

Compared with traditional silicone sealant, polyurethane sealant has a tensile elongation of more than three times and a bonding strength of more than twice. The single-component polyurethane sealant is non-toxic after curing and can be used in drinking water projects. 

Polyurethane sealant is widely used in various fields such as building joint sealing (concrete structure joints, curtain wall systems, window and door installations), waterproofing projects (roof waterproofing, basement waterproofing), infrastructure sealing (bridges, tunnels, subways), and decoration projects. 

03 Polyurethane Sealant: Applications in Special Environments 

Sulfurized sealant is based on liquid polysulfide rubber and is divided into two types: single-component and two-component. The single-component type is cured by moisture; the two-component type is cured by chemical reaction. 

This type of sealant has excellent properties such as resistance to oil, solvents, aging, acid and alkali. It has an extremely low air permeability and is heat-resistant, water-resistant, has good elasticity and stable adhesion. 

The application of polysulfide sealant requires strict adherence to the procedures: including preparatory work, base surface treatment, filling of gaps, surface smoothing, curing and hardening, and inspection and acceptance. The construction environment temperature should be between 5℃ and 35℃. Avoid construction in high-temperature or low-temperature conditions. 

The specific construction method of two-component polysulfide sealant is rather complex: A and B components need to be mixed evenly in a ratio of 100:10 to 100:14 by weight. Mechanical stirring should last for no less than 6 minutes, and manual stirring should last for no less than 9 minutes. During the mixing process, bubbles should be prevented from entering. The prepared sealant should be used up within 2 hours. 

04 Modified Silane Polymer Sealant: An Eco-friendly New Option 

Modified silane polymer sealant (such as MS sealant) is a one-component, neutral curing, solvent-free high-performance building sealing material. It is renowned for its outstanding weather resistance, aging resistance and chemical resistance. 

This type of sealant is environmentally friendly and does not contain volatile organic compounds (VOCs). It is friendly to the environment and human health. Its neutral curing property means that no acidic substances are produced during the curing process, making it friendly to substrates such as metals and concrete. 

The modified silane polymer sealant has high elasticity and can adapt to the minor changes of the joint, preventing the formation of cracks. At the same time, it has good adhesion to various materials, such as concrete, metal, and glass. 

It is widely used for sealing at various building joints (such as doors and windows, curtain walls, roofs), waterproofing treatment (for roofs, basements, tunnels), sealing of bridge joints, as well as sealing and waterproofing of equipment and structures in industrial buildings. 

05 Acrylic sealant: Economical and practical type 

Acrylate sealant is based on polyacrylate resin. The product is a squeezable and viscous fluid, usually in single-component and multi-component packaging. The majority of the products are in emulsion form, and solvent-based products are rarely seen. 

Emulsion-type acrylic sealant is low in cost and can be used on damp interfaces. It cures by evaporation of water. This type of sealant is free from solvent toxicity. After curing, it is resistant to water, aging and oil. It has sufficient elongation and adhesion. 

The silicone-modified acrylic sealants that have emerged in recent years possess superior properties, especially their water resistance and aging resistance are much higher than those of ordinary acrylic sealants. 

It is mainly used for sealing the internal joints of buildings, such as the joints of exterior wall panels, windows, door frames and installed glass, etc. In places that require mold prevention, such as kitchens, bathrooms and toilets, there are also specially designed mold-resistant acrylic sealant products. 

06 Technical Standards and Performance Requirements 

Chinese building sealants have a complete technical standard system, which mainly includes: 

- GB/T 23261-2009 "Building Sealant for Stone Materials"
- GB/T 14683-2017 "Silicone and Modified Silicone Building Sealants"
- GB 16776-2005 "Building Silicone Structural Sealants"
- GB/T 24267-2009 "Flame Retardant Building Sealant"
- T/CECS 10185-2022 "Sealants for Prefabricated Buildings" 

These standards have specified various parameters for building sealants, including **chemical resistance, elongation at break, viscosity, fire resistance, and weather resistance**, providing unified technical specifications for the production, inspection, and acceptance of sealants. 

In terms of international standards, the ISO 11600 standard has classified the physical and mechanical properties of sealants. Based on this, various countries have also formulated their own national standards. 

07 Application Areas and Selection Guide 

Adhesive sealant is widely used in the construction industry, mainly including: 

- Curtain wall system: Sealing between the panels and frames of glass curtain walls, aluminum plate curtain walls, and stone curtain walls, which adapts to structural deformation and maintains airtightness and watertightness.
- Door and window installation: Sealing between the door and window frames and the walls, preventing air leakage and water seepage, and enhancing energy efficiency.
- Concrete structure joints: Sealing for expansion joints, settlement joints, and construction joints of concrete components such as floor slabs, walls, beams, and columns, to prevent water and gas penetration.
- Waterproofing projects: Sealing for joints of metal roofs and concrete roofs, resisting ultraviolet rays, temperature changes, and rain erosion.
- Infrastructure sealing: Sealing for structural joints of bridges, tunnels, subways, and pipe galleries, to prevent groundwater infiltration and the leakage of harmful gases. 

When making a selection, the following factors need to be taken into consideration: 

-  Single-component vs. Two-component: The single-component is easier to apply and suitable for small areas or quick repairs; the two-component has more stable performance and is suitable for large areas or projects with high durability requirements over the long term.
- Displacement capacity level: Select based on the deformation amount of the joint (such as ±12.5%, ±25%, ±50%), to ensure that the sealant has elastic matching.
- Environmental protection requirements: Choose products with low VOC (volatile organic compounds), in line with indoor air quality standards. 

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The development of sealant technology is advancing rapidly. In the future, more emphasis will be placed on environmental performance, ease of application, and long-term durability. With the popularization of the concept of green buildings, sealant products with low VOC, no solvents, and biobased materials will become the mainstream in the market. 

New products such as modified silane polymer (MS) sealant have overcome the contamination defects of traditional sealants at the mechanism level. They do not cause hydrophobicity around the joint, thus avoiding the adhesion of contaminants. This characteristic is particularly important in the application of porous materials such as stone and concrete. 

Over the next five years, with the advancement of urban renewal and green building policies, the sealant industry will undergo deeper technological changes and experience a growth in market demand, providing safer, more environmentally friendly and more efficient sealing solutions for the global construction industry.