What Is Concrete Sealant?

Building sealants are mostly synthetic adhesives, whose main body is polymer, and their properties can be divided into three categories: bulk properties, process properties, and use properties (product performance).

The bulk properties depend on the chemical properties and physical structure of the main polymer of the sealant, which can be accurately and repeatedly measured. Process properties refer to the relevant characteristics exhibited by the sealant during the manufacturing process. It is self-evident that the nature of use (product performance) mainly refers to the comprehensive performance of the sealant during the formation of the cementation to the formation of the cemented joint, which depends on the functional requirements of the sealant on the building joints. Regardless of the outer envelope of the building or the interior decoration of the building; whether it is a window structure or other forms of envelope and decoration structure, they can be regarded as a unit composition, and then there will be a seam between each unit. Most require building sealants to seal and fill. The rational design of building joints, the understanding of building sealants, the reasonable selection of materials and the correct construction of building seals are all necessary processes to ensure the success of building joint seals.

The functional requirements of the building sealant mainly depend on environmental factors: including radiation aging in the sun, oxidation of oxygen and ozone, erosion of water and water vapor, the influence of environmental temperature changes, the effects of wind loads, shear forces, and cycling Mechanical (compressive / tensile) loads, invasive air pollution (such as acid rain, salt spray, etc.), the effects of microorganisms and macro organisms (fungi, etc.). After understanding the environmental factors and considering the needs of building joints, the functions of building sealants can be summarized as the following functions: building waterproofing, sound insulation, energy saving, corrosion protection, pollution prevention, fire protection, decoration, structural elastic connection, structural safety and durability.

1.Classification by basic polymer

Including: silicone, polyurethane, polysulfide, acrylic, butyl, asphalt and oil-based resin modified products. Among them, silicone, polysulfide, polyurethane three room temperature curing elastic sealants are most widely used in China, especially silicone sealant products.

Because of its special molecular structure, silicone sealants have the characteristics of both inorganic and organic polymers. The original gum of silicone gum is a polymer composed of Si-O as the main chain. Its bond energy is 106Kcal / mol, while the CO and CC bond energies of common polymer materials are relatively small, 80 and 85.2cal / mol, respectively. In other words, if the Si-O chemical bond is broken, a higher energy will be necessary, Therefore, the silicone adhesive is stable and has outstanding characteristics of UV resistance, ozone resistance, weather resistance, temperature resistance, and one-component and two-component applications in various forms. At the same time, products with different performance requirements can be manufactured according to the needs of the building. , Especially in the structural bonding application of hidden frame glass curtain wall, other materials are irreplaceable. And the development of China's raw material industry in the production of silicone sealants is relatively large and mature in terms of polysulfide and polyurethane. At present, silicone construction sealant products account for more than 60% of China's construction sealant usage. Modified silicone products are also widely used in construction abroad. At present, China is limited to other fields.

As early as the 1960s, the polysulfide sealant for construction was used in the oil and solvent-resistant bonding seals in the fields of aircraft and aviation. In the 1980s, it was also used in the sealing of construction joints. High, has been basically replaced by silicone products. However, the polysulfide sealant has good gas permeability and oil and solvent resistance characteristics, and is still widely used in the manufacture of insulating glass, and some of it is used for anticorrosive sealing of construction joint sewage, garbage dumps, oil storage structures and steel structures.

The diversity of polyurethane molecular structure can make different products with a wide range of modulus, which is suitable for the bonding of many materials. And because of its flexible molecular chain, it has good vibration resistance and fatigue properties. It is particularly suitable for bonding different materials and bonding to flexible materials. It also has very good low temperature resistance and is used in many industries. Very extensive. In the field of construction, the application of this material in the United States, Japan, Germany and other developed countries is close to that of silicone products. At present, due to the backwardness of the raw material industry in China, the development of sealant products is subject to certain restrictions. In addition, there are butyl, acrylic, asphalt, and oil-based resins with less elastic sealing paste products. This type of product has low elasticity and can be applied to parts with low mechanical displacement requirements of building joints. ^[1]

Silicone building sealant is a new type of waterproof sealing material. The storage conditions are protected from light, ventilation and moisture. It has the characteristics of good bonding performance and wide temperature range.

After curing, it has excellent weather resistance and excellent resistance to ultraviolet, high and low temperature, corrosion and temperature. The neutral dealcoholization type cures at room temperature. When the temperature difference changes greatly, the curing agent can also be adjusted to cure.

Its typical physical properties can form excellent structural strength at -30 ° C to 120 ° C. Primer two-component silicone sealants are generally not required to be primed, but if the adhesion test report indicates that primers are required, apply a primer to the base with a clean, lint-free cloth before applying sealant Spread a thin layer and allow it to dry. Testing must be done before applying the sealant to determine if a primer is required. ^[2]