Building silicone sealant is a hydroxy-terminated polydimethylsiloxane as the basic raw material, supplemented by crosslinking agents, fillers, plasticizers, coupling agents, catalysts and other additives in the vacuum mixed paste, in the product form is divided into a single component and two components, the use of single-component sealant is simple, do not weigh and mix before construction. After construction, with the help of moisture in the air or low temperature thermal activation to complete cross-linking curing, two-component sealant, mixed proportionally before use, with the help of cross-linking agent for cross-linking curing. Because the polymer molecule has a siloxane chemical structure on the main chain, it is called silicone sealant. The following is a brief introduction to the role of various ingredients:
1, polydimethylsiloxane is the basic component of silicone sealant, commonly known as "107 base glue", is a colorless transparent viscous liquid, it gives the basic properties of the material: sealing, waterproof, weather resistance, high and low temperature resistance. The molecular structure of 107-based adhesive is based on Si=O chemical bond, and its chemical bond energy is higher than the energy of ultraviolet light, so it has outstanding anti-ultraviolet light ability, which is difficult to compare with polyurethane sealant, polysulfide sealant, acrylic sealant and so on.
2, the crosslinking agent is a multifunctional silane compound, which can chemically react with 107 base glue, so that 107 base glue from the chain molecule into a network crosslinking system, from the appearance of the sealant curing process. Different types of crosslinking agents are used to release different small molecules during curing. According to the types of small molecules released, building silicone sealant can be mainly divided into deacetic acid type, deketone oxime type, dealcohol type, deamide type, etc.
3, the coupling agent is also a multifunctional silane compound, its main role is to improve the bond strength and bond range of the sealant. Building silicone sealant can stick to a variety of building materials is mainly its credit.
4, the use of building silicone sealant filler is mainly active nano-calcium carbonate and white carbon black, their role is to change the sealant mechanical properties (such as: elasticity, strength) and rheological properties (fluidity, extrusion).
5, building silicone sealant plasticizer is generally used inert polysiloxane, commonly known as silicone oil, mainly used to improve the elasticity, consistency and extrusion of sealant. Silicone oil and 107 base glue are siloxanes, with good compatibility, can remain in the sealant for a long time; Some sealant in order to reduce costs, the use of mineral oil as a plasticizer, such as No. 105 white oil, because mineral oil and 107 base glue is not a system, in the sealant will be completely released from the colloid after several months of use, resulting in sealant loss of elasticity, aging and cracking, in addition, white oil will dissolve the insulating glass sealing with hot melt butyl glue, stone pollution and other hazards.
6, in order to improve the curing speed of building silicone sealant, it is necessary to add a catalyst in the colloid, and organometallic complexes are generally selected. In the production of sealant, the catalyst is adjusted according to the actual use needs, the main consideration is the seasonal temperature change.
7, a variety of colors of sealant are mainly modulated with pigments, such as black carbon black, white titanium dioxide, various colors of metal compounds. Among the various colors of sealant, black has good performance, and general structural adhesives are recommended to use black.
8, some sealant need to increase special ingredients to improve some aspects of performance, such as flame retardants can make sealant flame retardant performance; The anti-mildew agent allows the sealant to inhibit the growth of mold.