What is the principle of waterproof coating?

The principle of waterproof coating is mainly to achieve waterproof function by forming a complete coating film and hydrophobic effect. ‌
Waterproof coating is a fluid or semi-fluid substance. After being coated on the surface of the base layer, it forms a continuous film with a certain elasticity and thickness through the volatilization of solvents or water, or chemical reactions between the components. This film can prevent the penetration of water molecules. Waterproof coatings are usually made by mixing base materials (such as acrylic polymers, synthetic rubber, synthetic resins, asphalt, etc.) and various additives (such as plasticizers, fillers, antioxidants, etc.).
Working principle of waterproof coating
Forming a complete coating film: A continuous and seamless waterproof layer is formed on the surface of the substrate through film-forming substances to prevent water penetration. After curing, polymer composite coatings can form a complete and continuous paint film. The width of the molecular gap is about a few nanometers. Single water molecules can pass through, but water in nature usually exists in an associated state, forming larger water molecule clusters, which are difficult to pass through the gap of the coating film.
Hydrophobic effect: Additives in the coating (such as hydrophobic agents) are used to change the surface properties of the coating, making it difficult for water droplets to stay on the surface, thereby enhancing the waterproof effect. In addition, some high-performance waterproof coatings also have a "breathing" function, that is, allowing water vapor in the wall to be discharged outward while preventing external moisture from entering to keep the structure dry.