For the development of a redispersible latex powder emulsion? -Huaqiang Electronic Network

Redispersible latex powder emulsion is a new generation of functional materials created by drying polymer emulsions. It has the unique property of being able to redisperse in water, forming an emulsion that closely resembles the original one. Compared to traditional lotions, redispersible polymer powders offer advantages such as easy handling, stable storage, convenient transportation, and environmental friendliness. They significantly improve the cohesion and flexibility of inorganic building materials, making them highly promising for future development. The key performance of redispersible latex powder is its redispersibility, but the mechanism behind it remains unclear. Understanding this process is crucial for improving the performance and development of polymer-based materials. In this study, we focused on the development of a redispersible latex powder emulsion, particularly examining its water dispersibility and film-forming water resistance. We prepared a water-resistant NMA-styrene-acrylic redispersible latex powder. The main findings of this research include: 1) **Stability Mechanism**: The use of ionizable hydrophilic monomers like MAA helps form a "fluff structure" and a thick hydration layer around the latex particles. This enhances protection during drying and increases surface charge density, which improves electrostatic repulsion and ultimately optimizes redispersibility. 2) **Diffusion Enhancement Mechanism**: During the spray-drying process, three key steps occur: (1) the surface of the emulsion droplets dries to form a protective shell, (2) the inner layer dries, causing the hydration layer to evaporate and create micropores, and (3) these pores expand to form continuous channels. When the powder is dispersed in water, moisture enters through these micropores, accelerating the breakdown of the powder into nano-sized particles similar to the original emulsion. 3) **Hydrophobic Association Mechanism**: Hydrophobic interactions within the polymer can inhibit the formation of the "fluff structure" and hydration layer, reducing surface charge density and hydrophilic group density. This leads to irreversible agglomeration when the particles dry. Upon redispersion, hydrophobic associations reduce osmotic pressure and hinder charge repulsion, which negatively affects water dispersibility and stability. 4) **Performance Optimization**: A novel NMA-styrene-acrylic latex powder was developed with both good water dispersibility and water resistance. The optimal synthesis formula includes: shell MAA monomer content at 6%, St/MMA mass ratio of 5/25, 0.33% emulsifier, 1% NMA monomer, and a spray emulsion pH of 8.5. The preparation of polymer latex powder and its redispersion in water involve a balance between hydrophobicity and hydrophobic association. The main factors contributing to effective dispersion are repulsive stability and the presence of microporous channels that allow rapid moisture penetration. These findings provide valuable insights for further advancements in redispersible latex powder technology.

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