Basic Knowledge of Waterborne Coating Formulation - Part 2: Waterborne Resins
In water based paint formulations, the base material is the key component that forms the paint film and determines its performance. When designing the formulation, the amount of waterborne resin should be maximized, accounting for 60-70% by volume, to ensure the highest possible content of effective film-forming agents in the paint. This guarantees a thicker, fuller paint film in a single coat. Waterborne Acrylic Resins Acrylic emulsions, due to their versatility, weather resistance, and diversity, have been widely used in various fields of the coatings industry. Waterborne acrylic emulsions are produced by emulsion polymerization of vinyl monomers, primarily acrylate monomers. Various additives, such as emulsifiers, stabilizers, and pH adjusters, are added during the polymerization process, making the system quite complex. Paint films made from waterborne acrylic emulsions have good weather resistance, are less prone to yellowing, have high hardness, and good gloss. In recent years, with the continuous development of waterborne acrylic emulsion polymerization technology, multiphase polymerization, core-shell technology, self-crosslinking technology, and the application of polymeric surfactants, the properties of waterborne acrylic emulsions have been further improved and enhanced. This has expanded the application range of waterborne acrylic emulsions to meet the needs of different construction and usage conditions. Currently, the application of waterborne acrylic emulsions has expanded to industrial applications with higher performance requirements. Polyurethane Dispersions Polyurethane materials are a general term for a class of macromolecular compounds with urethane structures in their molecular structure, usually produced by polyaddition reactions of diisocyanates and polyols. Polyurethane polymers possess both polar functional groups that enable physical crosslinking and non-polar and flexible segments. When used properly, their polar functional groups can undergo further chemical crosslinking. These molecular characteristics give polyurethane materials high strength, toughness, and solvent resistance. As a high-strength, weather-resistant, and strong-adhesion material, polyurethane has been widely used in the coatings industry. Based on the type of isocyanate used in the preparation of polyurethane, polyurethane emulsions and corresponding paints can be divided into two main categories: aliphatic and aromatic. Aliphatic paint films exhibit excellent weather resistance and anti-yellowing properties; aromatic waterborne polyurethanes are mostly used for interior decorative paints. According to the particle size obtained from polymerization, polyurethane emulsions and polyurethane dispersions are also classified. Waterborne polyurethane dispersions utilize a unique process to disperse polyurethane particles in water, thereby achieving film formation with water as the carrier. Similar to the film-forming mechanism of other emulsions, the film-...
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