Discuss the waterproofing mechanism of waterproof coatings

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There are a wide variety of waterproof coatings, but their waterproofing mechanisms can be divided into two categories: the film-forming type and the hydrophobic type. 1. Waterproofing mechanism of film-forming waterproof coatings: Film-forming waterproof coatings provide waterproofing by forming a complete film that prevents water from passing through or water molecules from penetrating. There are always some gaps between many coating molecules, with a width of several nanometers; in theory, a single molecule should be able to pass through these gaps. However, water in nature is usually in an associated state, with dozens of water molecules forming large clusters due to hydrogen bonds, which makes it difficult for them to pass through the gaps between the molecules. This is the main reason why waterproof coatings possess waterproofing properties. The waterproofing principle of acrylic emulsion is film-forming. 2. Waterproofing mechanism of hydrophobic waterproof coatings: Since some polymer molecules contain hydrophilic groups, a complete and continuous coating layer formed by these polymers does not guarantee that all such coating layers will have good waterproof properties. If the polymer itself has hydrophobic properties, resulting in complete incompatibility between water molecules and the coating film, then the problem of water molecule penetration can be resolved at its root. Polysiloxane waterproof coatings are designed based on this principle.