Fabrication of Nano-Silver–Silver Ion Composite Antibacterial Agents for Green Powder Coatings

Abstract

Nano-silver is characterized by broad-spectral, strong and stable antibacterial properties, which make it a promising material in coating applications. However, the efficiency of nano-silver is generally low in the coating of films. Here, we developed a series of highly active and durable silver ions–nano-silver antimicrobial agents for powder coatings. To optimize antimicrobial activity and durability, two different nano-silver generation methods, i.e., in situ and ex situ methods combined with different carrier materials, i.e., zeolite with high ion-exchange ability and montmorillonite of layered structure were adopted and investigated. All four antibacterial additives show high activity with a reduction rate of over 99.99% and R value of over 5. The ex situ generated nano-silver antibacterial agents with both carriers exhibit higher activity in the initial antibacterial property and antibacterial durability that the coating films are able to maintain over 99% antimicrobial reduction after 20 cycles (1200 times) of soap solution wiping. They also show a lower yellowish color difference of less than three compared to the films with in situ generation method. The one with montmorillonite as carrier shows the stronger antibacterial property with an R value of 5.88 and slightly better film appearance of lower color difference, smaller reduction in gloss and increase in haze as compared to zeolite carrier due to the layered structure.

Effect of Carrier Materials for Active Silver in Antibacterial Powder Coatings

“…Carrier materials should have some important parameters, including unique characteristics in cation exchange capacity and pore structure, as these aspects influence the function of the active components. It is widely reported that zeolite-and clay-based materials can serve as carriers for silver ions [12][13][14]. Zeolite carriers possess a framework of silicate with high adsorption and ion exchange capabilities, which permits them to act as inorganic reservoirs for silver ions [15][16][17][18].…”