- The following construction steps are the basic requirements for applying construction sealants. Strictly following these construction steps can ensure that the sealant has good performance, which is also a necessary condition for obtaining quality assurance. Because construction silicone adhesives are used in many different environments , this construction step cannot be used as a quality assurance document covering everything.
- Scope of application
It is suitable for the construction silicone sealant series products produced by our company.
- Construction environment
The sealant should be constructed in a clean environment with a temperature of 4-40 °C and a relative humidity of 35% -75%. Ambient temperature is too low will reduce the adhesion of the sealant, because the surface wettability of the sealant is reduced, and frost and ice may form on the low-temperature substrate, affecting the adhesion of the sealant. Therefore, the safe use temperature of the sealant should be greater than 5 ℃. High ambient temperature also has an adverse effect on the sealant. On the surface of the building with excessively high ambient temperature and direct sunlight, the actual temperature of the substrate surface may be higher than the ambient temperature Much higher. Due to the influence of high temperature, the sag resistance of the sealant will be poor, because the time for chemical conversion will be faster, the use time and the trimming time will be shortened, and at the same time it is easy to generate bubbles. If the relative humidity is too low, the seal ant will slow down. The excessively high relative temperature may form a film of condensed water on the surface of the substrate, affecting the adhesion between the sealant and the substrate, and may also cause the sealant to form bubbles. .
On-site adhesion testing must be performed to ensure good adhesion of the glue and verify any recommendations regarding glue. (See the chapter on quality management)
There are five basic requirements for the correct interface surface cleaning and glue application:
- The interface surface must be clean, dry, free from dust pollution and free from freezing.
- If primer is required, the primer must be applied to a clean surface.
- If necessary, use backing materials or release tape.
- Fill the gap of the interface with glue when applying glue.
- The leveling work is to ensure that the glue has the correct shape and can completely contact the substrate.
2.Surface treatment of the substrate and the application of silicone
- Material cleaning steps
This chapter discusses cleaning solvents and basic cleaning steps for porous / non-porous materials. The adhesion between the sealant and the substrate depends on whether the substrate surface is clean. The user should contact the supplier of the substrate to ensure that this cleaning step and the selected cleaning solvents are compatible with the substrate.
A) Use of organic solvents
Not every solvent can effectively remove every contaminant. Some solvents will seriously damage a certain material, please follow the solvent manufacturer’s safe use recommendations and local or national solvent use regulations.
Isopropyl alcohol may not effectively remove contaminants on polyester dust coating materials. Xylene is recommended to clean this material.
B) Non-porous materials
Before applying glue, the surface of the non-porous material must be cleaned with a solvent. The choice of solvent depends on the contaminant and the substrate. Non-oily dust and dirt can be removed with 50% water and 50% isopropyl alcohol. Oily dirt and film should be removed with a degreasing solvent such as xylene.
C) porous material
Building materials such as cement boards, concrete, granite, limestone, other stone materials or cementitious materials, and substrates that can absorb liquids are considered porous materials.
For some new porous materials, dusting may be sufficient. Depending on the surface treatment, the surface of the porous material needs to be abraded to clean, some to be cleaned with a solvent, and some to both. The float and dust on the cement board must be cleaned. Fine silicon dust, water repellent and other surface treatment residues on the surface of the cement substrate, protective coatings and old sealants all affect the adhesion of the adhesive. In order to ensure good adhesion, the above surface residues, coatings and old sealant residues must be removed by grinding. Abrasive cleaning methods include grinding, sawing, washing with sand or water, mechanical grinding or a combination of the above methods. Use wire brush, vacuum cleaner and compressed air without oil to remove dust and loose particles on the surface. Once the surface is clean and dry, the glue can be applied. If the surface is dirty, it must be cleaned with a solvent using the “two rag cleaning method” (described in detail later). Some porous materials will absorb solvent