Abstract: Aiming at the long-term weather resistance demand of super-hydrophobic coatings for outdoor equipment, this study developed a super-hydrophobic coating system based on silicone rubber matrix. Through the combination of sol-gel method and powder spreading method, a micro-nano dual-scale rough structure was constructed, and the preparation mechanism, surface morphology regulation and weather resistance of the coating were systematically studied. Experiments show that the coating still maintains super-hydrophobicity (contact angle > 150°) in extreme environments (low temperature, salt spray, ultraviolet, mechanical wear), providing high-performance protection solutions for 5G communications, power insulation and marine equipment.
Coating preparation process and mechanism
Sol-gel method to construct low surface energy system
Using terminal hydroxyl fluorinated polysiloxane as film-forming material and 1H,1H,2H,2H-perfluorooctyl triethoxysilane as modifier, a three-dimensional network structure is formed through hydrolysis condensation reaction. Add precipitated silica (particle size 20-40 nm) and fluorocarbon solvent, and use silane coupling agent (KH-570) to achieve inorganic-organic interface bonding. During the transformation of sol into gel, fluoride migrates to the surface in a directional manner to form a low surface energy layer (surface energy <10 mN/m), and at the same time, silica nanoparticles self-assemble into a porous structure with a contact angle of 153.2°±0.2°.
Powdering method to construct micro-nano rough structure
Using high temperature vulcanized silicone rubber (HTV) as the matrix, silica powder (particle size 5-15 μm) is sprinkled and cured at 180°C. The phase separation effect during the curing process of PDMS causes the silica particles to embed into the matrix, forming a micro-nano composite structure similar to a lotus leaf (fractal dimension 2.3-2.7). The surface roughness (Ra) reaches 35.695 μm, the contact angle is increased to 157.7°, and the rolling angle is less than 5°, achieving a self-cleaning function.
Weathering performance optimization strategy
Enhanced environmental adaptability
Improved UV resistance of coating by fluoride modification: After 30 cycles of alternating ultraviolet irradiation (313 nm) at 60°C and condensation at 50°C, the contact angle only dropped to 161.1°, and the superhydrophobicity was still maintained. After the salt spray aging test (35°C, 5% NaCl solution, 500 h), the coating surface was not corroded, and the contact angle was stable at more than 152°, thanks to the physical barrier effect of silica and the chemical inertness of fluoride.
Improved mechanical stability
A double-layer structure is used to enhance wear resistance: the bottom layer is a PDMS/silicon dioxide composite layer, and the surface layer is a fluoride modified layer. After 300 sandpaper abrasions (load 500 g), the contact angle is still 159.9°, and the rolling angle is 7.5°, which is better than a single-layer coating (contact angle after abrasion <150°). In addition, the coating showed no cracking after thermal shock cycles (100 times) from -18°C to 150°C, and had excellent thermal expansion coefficient matching.
Typical application cases
5G antenna cover anti-rain attenuation
In the simulated rainfall test (48 h, rain intensity 10 mm/h), the contact angle of water droplets on the surface of the coated antenna cover was 165.1°, the rolling angle was <3°, and the signal loss (-0.05~-0.28 dB) was reduced by more than 90% compared with the uncoated antenna cover (-3.71~-5.17 dB), effectively solving the rain attenuation problem of 5G base stations.
Anti-pollution flashover of power insulators
Superhydrophobic coating is applied to 110 kV composite insulators. In the artificial pollution (NaCl+diatomaceous earth, ash density 2.0 mg/cm²) test, the flashover voltage is increased by 29.0% (mild pollution) and 42.9% (severe pollution) compared with ordinary RTV coating, which significantly improves the reliability of transmission line operation.Conclusion and Prospect
This study achieved a breakthrough in the weather resistance of silicone rubber superhydrophobic coatings through material design and structural optimization.
Future research will focus on:
Developing green solvent systems to reduce VOC emissions;
Integrating luminous and conductive functions to expand application scenarios;
Optimizing the spraying process to achieve large-scale industrial production.
This coating has important promotion value in the field of outdoor equipment protection and can provide long-term protection solutions for smart grids, 5G communications and marine engineering.
