Stabilized, highly light-blocking microcomposite coating based on size-controlled polystyrene microspheres for paper surface engineering

Environmentally friendly waterborne coatings have attracted significant interest in the paper industry. However, the poor compatibility of masking materials with coating matrices often compromises film formation, adhesion, and stability, thus driving the need for high-performance alternatives. To tackle this challenge, monodisperse polystyrene microspheres (∼1.35 μm) with exceptional light-blocking properties were successfully synthesized through a simple yet optimized dispersion polymerization approach. These microspheres were subsequently incorporated into styrene-acrylic latex (SAL) to develop a microcomposite coating system. The resulting microcomposite coating showed a significant reduction in UV–vis transmittance, decreasing it to below 25 %. This represented a 70.16 % (±2.02 %) reduction in maximum transmittance compared to the pristine SAL coating. Furthermore, the microcomposite coating demonstrated superior environmental durability under various conditions, including aqueous, ethanol, saline, acidic, alkaline, UV light and cyclic mechanical stress conditions. When applied to paper substrates, the microcomposite coating significantly enhanced both optical and mechanical properties, outperforming conventional masking materials. In addition, the coated paper was fully biodegradable under natural conditions within 30 days. Notably, the residues from the polymerization process exhibited exceptional reusability, consistent with the principles of the circular economy. This study presents a green synthesis approach for high-performance waterborne coatings, combining exceptional light-blocking efficiency with robust stability, with potential applications in papermaking, construction, and automotive industries.