Scrub resistance is one of the core performance indicators of water-based multifunctional paint, directly affecting the coating's appearance retention and functional stability over long-term use. Achieving this performance is closely related to the selection of resin components and formulation design. Key components such as waterborne acrylic resin, waterborne polyurethane resin, waterborne epoxy resin, and waterborne alkyd resin, through different molecular structures and film-forming mechanisms, collectively determine the coating's physical strength, chemical stability, and weather resistance.
Waterborne acrylic resin is one of the most commonly used film-forming substances in water-based multifunctional paint. Its molecular chains contain acrylate or methacrylate monomers that form a linear or slightly cross-linked structure through copolymerization. This structure gives the coating a good balance of flexibility and hardness: flexibility makes the coating less prone to cracking under external scrubbing, while appropriate hardness resists scratches and abrasion. Furthermore, functional monomers, such as acrylates containing hydroxyl or carboxyl groups, can be introduced into the acrylic resin molecular chain. These groups not only enhance the coating's adsorption capacity for pigments and fillers but also form a denser network structure through cross-linking reactions, further improving scrub resistance. Waterborne polyurethane resins achieve optimized scrub resistance through their unique soft-hard segment structure. The polyurethane molecular chain consists of flexible polyether or polyester soft segments and rigid isocyanate hard segments. The soft segments impart elasticity to the coating, allowing it to disperse stress through deformation under load; the hard segments provide mechanical strength, preventing the coating from being abraded. Waterborne polyurethane is often prepared using a self-emulsification method, introducing hydrophilic groups (such as carboxylates or sulfonates) into the molecular chain, enabling it to be stably dispersed in water. Coatings formed by this dispersion exhibit excellent adhesion and abrasion resistance, making them particularly suitable for applications requiring frequent cleaning.
Waterborne epoxy resins derive their scrub resistance from their high crosslinking density and excellent chemical stability. The epoxy groups in the epoxy resin molecule can undergo ring-opening reactions with curing agents (such as amines or acid anhydrides) to form a three-dimensional network structure. This structure not only gives the coating extremely high hardness and abrasion resistance but also effectively resists the erosion of chemical media. In water-based systems, epoxy resins require emulsification or dispersion techniques to achieve water-based properties. Although their scrub resistance is slightly inferior to solvent-based systems, optimized formulations (such as using reactive diluents or nanofillers) can still meet the requirements of most applications.
Water-based alkyd resins, on the other hand, enhance scrub resistance through their unique ester bond structure and pigment/filler dispersibility. Alkyd resins are formed by the condensation of polyols, polyacids, and fatty acids. The ester bonds in their molecular chains can form cross-linked structures during film formation, enhancing the coating's cohesion. Simultaneously, alkyd resins exhibit excellent wettability and dispersibility for pigments and fillers, forming a uniform and dense coating and reducing weak points caused by uneven pigment/filler distribution. Furthermore, the flexibility of alkyd resins makes them less prone to cracking during scrubbing, thus extending the coating's lifespan.
In practical applications, water-based multifunctional paints often maximize scrub resistance through composite resin systems. For example, blending waterborne acrylic resins with waterborne polyurethane resins can combine the advantages of both to form a coating that is both flexible and wear-resistant; or introducing acrylate monomers into waterborne epoxy resins can improve their flexibility and workability through copolymerization. Furthermore, the addition of nanomaterials (such as nano-silica or nano-calcium carbonate) can further fill the micropores in the coating, improving its density and hardness, thereby enhancing its scrub resistance.
