Abstract
An efficient and simple method for preparing bonded metallic powder coating is in high demand in the paint manufacturing and application industries. The bonding purpose is to keep the mass percentage of metallic pigment consistent between the original and recycled coating powder, which aims at solving the problem of recyclability. One possible method capable of realizing this goal is using the binder to cohere metallic pigment with base particles through a cold bonding method. Through this approach, the pre-curing and high-reject-rate problems generally present in thermal bonding can be completely eliminated. In this paper, polyacrylic acid (PAA) and polyvinyl alcohol (PVA) are applied as binders for the bonding process. At various dosages of liquid binder and D.I. water, bonded samples with different bonding effect were prepared. Finally, a good bonding quality with the lowest variance between the mass concentrations of Al flakes in the original powder (before spray) and deposited powder (after spray) 2.94% with PAA as a binder and 0.46% with PVA as a binder was achieved. These results manifest that the cold bonding method is a green and simple approach for preparing the metallic powder coating.
Highlights
Metallic powder coating, which is a powder coating incorporated with metallic pigment(s), has been gaining increased market share in recent years [1,2,3,4,5]
Powder coatings are dry paints formulated with resins, pigments, and additives, which are similar to the solvent borne paints with the exception of no solvent present; while metallic pigments, such as aluminum, copper, nickel and zinc, are introduced for providing better aesthetic appearance and protection
All metallic powder coatings were non-bonded, which means that a powder base coat was prepared and metal flakes were dry-blended into the powder to create a metallic effect [11,12,13]
Summary
Metallic powder coating, which is a powder coating incorporated with metallic pigment(s), has been gaining increased market share in recent years [1,2,3,4,5]. The sharp distinctions between base particle and metallic flake, such as shape, surface conductivity, volume and mass, result in a difference in the concentrations of the metallic pigment in the final film and the original coating powder when using the electrostatic spraying process, which is the main spraying method in the powder coating industry due to its ability to realize full-automatic painting with thick films (50–300 μm) on a large scale [16,17,18]. The sticky surface of the base particles glue up the metallic flakes This approach solves the problems in the non-bonding and melt-extrusion methods, and gives the product a shiny and uniform final appearance. After a detailed investigation on the dependence of bonding quality on different binder-water formulas, the optimal formula was determined, and a simple and economic cold bonding method was developed
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