As a building exterior wall coating material, hydrophobic silicate sol's weather resistance and anti-penetration performance are related to the service life and safety of the building.
First, the performance is optimized by adjusting the chemical composition of the sol. In hydrophobic silicate sol, the integrity of the silicon-oxygen network structure directly affects the coating performance. In the preparation process, it is crucial to reasonably control the modulus of silicate (i.e., the molar ratio of silicon dioxide to alkali metal oxide). Sols with lower modulus have high alkali metal oxide content, fast initial film formation but poor weather resistance; sols with higher modulus have high silicon-oxygen polymerization degree and can form a denser network structure, which can significantly improve weather resistance and anti-penetration ability. In addition, the introduction of organosilicon modifiers, using their special silicon-carbon bond structure, cross-linking reaction with hydrophobic silicate sol, forming an organic-inorganic hybrid network on the coating surface, not only retains the hardness and weather resistance of inorganic materials, but also gives the coating a certain flexibility and hydrophobicity, effectively blocking water penetration, while enhancing the coating's ability to resist erosion by harsh environments such as ultraviolet rays and acid rain.
Secondly, optimizing the preparation process of sol is of great significance to performance improvement. The particle size and distribution uniformity of sol will affect the microstructure of coating. The sol particles can be refined and the particle size distribution can be narrower by using ultrasonic dispersion, mechanical stirring and high-pressure homogenization. Sol with uniform particle size can form a smoother and denser coating during coating, reduce pores and defects, and thus improve the anti-permeability performance. At the same time, precise control of sol aging time and temperature is also indispensable. Properly extending the aging time can promote the further polymerization of silicon oxygen bonds in the sol and enhance the stability and film-forming property of the sol; while a reasonable aging temperature can accelerate the reaction process, avoid the sol gelling too fast due to high temperature, or the reaction is incomplete due to low temperature, which affects the final performance of the coating.
Furthermore, adding functional fillers is an important way to optimize performance. Fillers such as nano-sized titanium dioxide and zinc oxide have good ultraviolet shielding ability. Evenly dispersing them in hydrophobic silicate sol can effectively absorb and scatter ultraviolet rays, reduce the damage of ultraviolet rays to the coating, and improve weather resistance. In addition, fillers such as flaky mica powder and glass flakes can form a "maze effect" inside the coating, extend the water penetration path, and significantly improve the anti-penetration performance. When adding fillers, it is necessary to control their dosage and particle size. Excessive dosage may affect the fluidity of the sol and the flexibility of the coating, while too large a particle size cannot fully exert its function. At the same time, a coupling agent is used to surface treat the filler to enhance the compatibility of the filler with the sol, prevent the filler from agglomerating, and ensure that the filler is evenly dispersed in the sol to give full play to its performance advantages.
Then, improving the construction process of the coating can also effectively improve the performance. Before construction, ensure that the wall base is flat, dry, and clean, which can enhance the adhesion between the coating and the base, reduce the cracking and peeling of the coating caused by base problems, and indirectly improve the weather resistance and anti-penetration performance. During the coating process, it is crucial to choose the appropriate coating method and number of coating layers. Spraying construction is efficient and can form a uniform coating, but there may be problems with uneven coating thickness; roller coating can better control the coating thickness, but the efficiency is lower. Generally, a multi-layer coating method is adopted, and the thickness of each layer of coating is controlled within a reasonable range, so that the coating is gradually dried and solidified to form a dense overall structure. The interval time of each layer of coating needs to be reasonably determined according to the drying characteristics of the sol. If it is too short, the coating may not be completely dried before the next layer is coated, affecting the coating quality; if it is too long, the coating surface may be polluted or aged due to environmental factors, reducing the performance.
Then, the introduction of nano-composite technology brings new breakthroughs for performance optimization. The nano-materials are compounded with hydrophobic silicate sol, and the small size effect and surface effect of the nano-materials are used to give the coating more excellent properties. For example, nano-silicon dioxide particles have a high specific surface area and strong surface activity, which can be closely combined with the silicon-oxygen network in the hydrophobic silicate sol, further filling the pores of the coating, improving the density and hardness of the coating, and enhancing the anti-penetration and weather resistance. Nano-silver particles have good antibacterial properties. Compounding them into the coating can not only improve the protective performance of the coating, but also prevent the coating surface from being damaged by microbial erosion, thereby extending the service life of the coating. In the process of nanocomposite, it is necessary to solve the problem of dispersion of nanomaterials, and adopt methods such as surface modification and ultrasonic dispersion to ensure that nanomaterials are evenly dispersed in the sol and give full play to their functions.
In addition, the development of intelligent coatings is also a cutting-edge direction for optimizing performance. By adding intelligent materials such as temperature-sensitive and humidity-sensitive materials to hydrophobic silicate sol, the coating can have self-regulation and repair functions. For example, after adding temperature-sensitive materials, when the ambient temperature changes, the coating can automatically adjust the microstructure, maintain good flexibility at high temperatures, and avoid cracking of the coating; enhance hardness at low temperatures to resist external impact. Humidity-sensitive materials can make the coating automatically shrink pores when the humidity is high, reduce water penetration; restore to its original state when the humidity decreases, and maintain good air permeability. This intelligent coating can dynamically optimize its own performance according to environmental changes, significantly improve weather resistance and anti-penetration capabilities, and provide a more efficient solution for the protection of building exterior walls.
Finally, establishing a scientific performance evaluation and monitoring system is the guarantee for continuous performance optimization. In the laboratory stage, the weather resistance of the coating is comprehensively tested by simulating harsh environments such as ultraviolet radiation, acid rain erosion, high and low temperature cycles, etc.; the anti-penetration performance of the coating is evaluated by using methods such as water pressure test and water vapor permeation test. In actual engineering applications, non-destructive testing technology is used to regularly monitor the thickness, adhesion, porosity and other performance indicators of the coating, timely detect changes in coating performance, analyze the causes and take targeted optimization measures. At the same time, combined with big data and artificial intelligence technology, a large amount of performance test data is analyzed, and the law of performance changes is summarized, providing a scientific basis for the application and performance optimization of hydrophobic silicate sol in building exterior wall coatings, and promoting its continuous development and improvement.
