High-performance metallic-effect powder coatings enabled by microwave energy

Metallic-effect powder coatings (MPCs), made of base powder coatings (BPCs) and metallic pigments (MPs), offer a metallic appearance and substrate protection. Their market growth is driven by zero VOC emissions and lower costs, compared to solvent-borne metallic-effect coatings (SMCs). However, MPCs typically add <2.0 wt% MPs, whereas the addition of MPs in SMCs is generally above 5.0 wt%. The relatively low MPs addition in MPCs restrict their further development. The challenge for MPCs is the instability of the metallic effect caused by the separation of MPs from the BPCs during the spraying. Traditional bonding using frictional energy and hot-water jackets often fails to maintain stability with higher MP contents. This study explores microwave energy as heating source for bonding method, showing that microwave-bonded MPC exhibit better metallic effects, and higher stability, especially at a high metallic effect of 8.0 wt% MP (Al flakes). This study offering a promising approach for MPCs with high MP concentrations.