The flexibility of silicone coatings (especially crack resistance in low temperature environments) comes from their unique molecular structure and modification technology, which enables them to maintain excellent elasticity and crack resistance under severe cold conditions. The following is a specific analysis:

1. Molecular structure gives low-temperature flexibility
The main chain of silicone coatings is composed of ‌Si-O-Si‌ bonds, with high bond energy (up to 422 kJ/mol) and large bond angle (140°), which allows the molecular chain to rotate freely at low temperatures to avoid rigid fracture.
The methyl and phenyl organic groups on the side chains provide steric hindrance effects, reduce intermolecular forces, and further enhance low-temperature deformation capabilities.
‌Low-temperature performance‌:

‌Pure silicone resin‌: Remains flexible at ‌-50℃‌, and the impact strength does not decrease significantly‌.
‌Modified silicone resin‌ (such as polyurethane/polyester modification): Cold resistance is improved to ‌-80℃‌, and the elongation at break is maintained at more than 200%.

2. The core mechanism of low-temperature crack resistance
‌Elastic deformation ability‌
The elongation of silicone coating at low temperature can reach 200%-300% (much higher than 50% of ordinary coatings), which can absorb the stress caused by thermal expansion and contraction of the base layer to avoid stress concentration and cracking.
‌Microstructure stability‌
After curing, an elastic rubber-like continuous film is formed. The molecular chain segment movement ability is still strong at low temperature, and it is not easy to undergo glass transition (Tg as low as -60℃).
‌Freeze-thaw cycle resistance‌
After 150 freeze-thaw cycle tests at ‌-40℃↔25℃‌, the coating has no cracking and peeling (3 times the national standard requirement).

3. Modification technology improves adaptability to extreme environments
‌Nanocomposite technology‌
Add fillers such as nano-silica to form an interpenetrating network structure, which enhances the tensile strength of the coating at low temperature (increased by 40%) and deformation recovery ability.
‌Organic-inorganic hybrid‌
Such as silane-modified polyether (such as Oriental Yuhong DMSC):
Remove unstable structures (-NCO groups) in the molecular chain to avoid low-temperature embrittlement;
Flexibility remains unchanged at -40℃, and supports construction at -10℃ (curing and film formation in 24 hours).
‌Optimization of hydrophobic groups‌
Introduce long-chain alkyl siloxane to reduce surface energy (contact angle>110°) and prevent water from penetrating and freezing and expanding to cause microcracks.

4. Engineering application verification and construction points
‌Extreme environment case‌
Harbin Ice and Snow World Hotel (-45℃): The silicone-modified coating has been used for 4 years without cracking, and the freeze-thaw damage area is less than 0.5%.
Transmission towers in high-cold areas: The coating inhibits ice adhesion in freezing rain environments and reduces structural loads.
‌Key control of construction‌
‌Temperature limit‌: Construction environment ≥4℃, avoid freezing due to low temperature uncured‌; ‌Coating thickness‌: Single coating ≤0.5mm, total thickness 1.0-1.5mm (too thick will shrink and crack); ‌Enhancement treatment‌: Add carcass cloth to the corners to improve the crack resistance of the stress concentration area‌.