What are the curing time of silicone waterproof coatings and their high/low temperature resistance after curing?

The curing time and temperature resistance of silicone waterproof coatings after curing are critical parameters in practical applications. Below is a comprehensive explanation:

I. Curing Time

1. Standard Curing Stages
   • Surface drying time: Approximately 2–4 hours (surface becomes non-tacky and can be lightly touched).
   • Full curing time: Approximately 24 hours (complete solidification, capable of bearing external forces or subsequent operations).
2. Influencing Factors
   • Temperature:
     • High temperature (>30°C): Accelerates curing; surface drying may shorten to 1–2 hours.
     • Low temperature (<10°C): Slows curing; surface drying may take 4–6 hours, and full curing may extend beyond 48 hours.
   • Humidity:
     • High humidity (e.g., rainy season) prolongs curing time; improve ventilation or use dehumidifiers.
   • Coating thickness:
     • Excessive single-layer thickness (>1mm) may lead to uneven internal curing; apply multiple thin layers instead.
3. Variations in Specialized Products
   • Single-component coatings: Rely on ambient humidity for curing; time is relatively stable.
   • Two-component coatings: Require proportional mixing; curing time is more controllable (e.g., fast-curing types may achieve full curing in 6–8 hours).

II. High/Low Temperature Resistance After Curing

1. Standard Product Temperature Ranges
   • High-temperature resistance: Withstands -40°C to 200°C long-term and up to 250°C short-term (e.g., thermal shock).
   • Low-temperature resistance: Maintains flexibility at -60°C without brittleness or cracking.
2. Enhanced Product Performance
   • High-temperature modifications: With additives like ceramic or aluminum powder, resistance can reach 300°C–400°C (suitable for boilers, exhaust pipes).
   • Ultra-low-temperature modifications: Phenyl-modified silicone formulations tolerate -100°C (for polar engineering or liquid nitrogen equipment).
3. Performance Characteristics
   • Thermal stability: Stable Si-O bonds resist oxidation and decomposition under prolonged high temperatures.
   • Low-temperature flexibility: High molecular chain mobility ensures bendability and elongation (>100% at -40°C).
   • Thermal cycling resistance: Withstands drastic temperature fluctuations (e.g., alternating between -30°C and 150°C) without cracking or delamination.

III. Precautions and Selection Guidelines

1. Application Tips
   • Avoid applying in rain or humidity >85%; use climate control if necessary.
   • Apply layers at 0.3–0.5mm thickness; ensure prior layers are surface-dry before recoating.
2. Product Selection
   • Standard environments: Choose coatings rated for -40°C to 200°C.
   • Extreme high temperatures (e.g., chemical plants): Opt for modified products rated above 300°C, verified by third-party tests (e.g., TGA reports).
   • Ultra-low temperatures (e.g., cold storage): Prioritize phenyl-modified or ultra-flexible formulations.
3. Verification and Maintenance
   • Post-curing, check hardness (e.g., Shore A hardness ≥50) or adhesion via pull-off tests.
   • For long-term exposure to extreme temperatures, regularly inspect for color changes or abnormal hardness.

IV. Typical Applications

• High-temperature fields: Metallurgical equipment, automobile engine compartments, solar panel backsheet sealing.
• Low-temperature fields: Cold chain logistics warehouses, ski resort structures, waterproofing for bridges in frigid zones.
• High thermal cycling environments: Desert building exteriors, aerospace component protection.