Researchers have optimized the spray drying process for vinyl acetate-ethylene (VAE) polymer dispersions to produce redispersible powder coatings (RPCs), a sustainable alternative to traditional waterborne coatings. RPCs offer biocide-free storage and reduce transportation weight, but challenges with powder production and film formation have limited their widespread use.

The study explored the impact of using different stabilizers—polyvinyl alcohol (PVA) and an emulsifier-PVA mix—on spray drying outcomes. Using PVA as a stabilizer significantly reduced particle size, achieving as small as 1.0 μm, and increased process yield to around 80%. In contrast, the emulsifier-PVA mixture produced larger particles, with a minimum size of 4.69 μm and a lower yield of 29.2%. The stabilization method also influenced the morphology of the powders, with PVA-stabilized particles forming agglomerated, raspberry-like structures, and emulsifier-PVA particles resulting in larger, spherical shapes.

The research further investigated how different glass transition temperatures (Tg) of the VAE polymers affected the coatings’ performance, particularly in terms of wet scrub resistance (WSR). Coatings formulated with low Tg emulsifier-PVA-stabilized VAE (EP-VAE) dispersions demonstrated enhanced film formation and higher WSR. In contrast, high Tg EP-VAE dispersions showed poorer WSR. PVA-stabilized VAE powders, however, failed to form coherent films, leading to complete washout after 200 scrub cycles. This issue was mitigated by adding a solid plasticizer to improve film integrity.

The findings highlight the potential of optimized spray drying processes and the choice of stabilizers in improving the performance of RPCs for architectural coatings.

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