Weather resistance of silicone coatings: How to deal with UV rays and extreme climates?
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Silicone coatings have demonstrated excellent performance in dealing with UV radiation and extreme climates due to their unique molecular structure (with Si-O bonds as the main chain) and material properties. The following are its core protection mechanisms and adaptive strategies:
1. Anti-UV mechanism: Molecular-level protection
Intrinsic resistance
Bond energy advantage: Si-O bond energy is as high as 452 kJ/mol, far exceeding UV energy (300-400 kJ/mol), which can effectively block UV damage to molecular chains.
Perfluorocarbon chain barrier: Modified silicone resin (such as adding phenyl) forms a dense protective layer with a UV reflectivity of up to 95%, reducing energy absorption.
Strengthening technology
Nanocomposite: Adding 5-15% nano-TiO₂ or ZnO particles, the UV absorption rate is increased to 99.5%, while enhancing the mechanical strength of the material.
Surface coating: PVDF/SiO₂ composite coating extends the weathering life by 3 times and is suitable for high radiation areas (such as deserts and plateaus).
II. Extreme climate adaptability 1. High temperature environment (-60℃~800℃) Thermal stability: The thermal expansion coefficient is as low as 8×10⁻⁶/K (300-800℃ range), and the structure is still intact after 200 thermal cycles. Oxidation resistance: A ceramic conversion layer (silicon carbide structure) is formed at high temperature to isolate oxygen erosion and protect the metal substrate.
2. Low temperature and humid and hot environment Flexibility retention: The glass transition temperature (Tg) is as low as -120℃, and the elastic modulus only increases by 5% at -80℃ to avoid brittle cracking. Moisture-proof and mildew-proof: Water vapor transmission rate ≥85g/m²·24h (3 times that of ordinary fluorocarbon resin), expel moisture from the base material, and prevent bubbling and falling off.
3. Scenarios with drastic temperature changes
After 1000 tests of -65℃~200℃ hot and cold shock, the volume change is <0.2%, and the bonding strength retention rate is >90%.
III. Weather resistance verification method
Accelerated aging test
UV fluorescent lamp aging instrument: Simulate outdoor ultraviolet rays, 200-1000 hours of testing is equivalent to 1-5 years of natural exposure, and observe the degree of powdering and discoloration (ΔE≤1.5 is qualified).
Salt spray test: Verify corrosion resistance, such as quartz tiles without rust after 2400 hours of salt spray test3.
Natural exposure data
PTFE tubes were exposed to the Arizona desert for 10 years, and the mechanical properties retention rate was >90%.
Pure silicone resin coating has no gloss loss or powdering after 12 years of outdoor exposure.
IV. Practical application scenarios
Building exterior walls
Metallic art paint coating: hydrophobic angle ≥110° (lotus effect), rainwater self-cleaning rate >90%, solving the problem of dust accumulation and weakening reflection11.
Quartz brick protection: Add titanium dioxide radiation layer, the brick surface temperature in summer is 22℃ lower than asphalt pavement.
Industrial equipment
Automobile exhaust pipe: Resistant to short-term high temperature of 800℃, reducing surface temperature by 60℃ and improving fuel efficiency by 2.3%.
Photovoltaic power station: The junction box protective sleeve has passed the "double 85 test" (85℃/85% RH), and the insulation resistance is >10¹² Ω.
Special environment
Coastal facilities: The salt spray corrosion resistance life exceeds 15 years, suitable for sealing the expansion joints of cross-sea bridges. Aerospace: Satellite cable sheaths withstand space ultraviolet radiation and -100℃~120℃ temperature differences
