1.How to choose the right antimicrobial agent?
Inorganic antimicrobial agents
Based on metal ions or their compounds, they can achieve antimicrobial effects by slowly releasing metal ions to destroy microbial cell membranes and inhibit enzyme activity. They are suitable for long-term use of color-coated coils.
Silver antibacterial agent:
Antibacterial mechanism: Silver ions can penetrate bacterial cell membranes, bind to DNA to prevent its replication, and destroy the intracellular enzyme system. They have a broad spectrum of antibacterial effects on Escherichia coli, Staphylococcus aureus, mold, etc., with an antibacterial rate of more than 99%.
Form: Nanosilver particles or silver-loaded carriers - the carrier can control the slow release of silver ions and extend the antibacterial life.
Advantages: high safety, good heat resistance, and strong weather resistance.
Organic antimicrobial agents (auxiliary or short-term scenarios)
Antimicrobial agents are used through chemical reactions (such as destroying cell membranes and inhibiting metabolism). They are effective quickly, but have poor durability and weather resistance. They are suitable for short-term antimicrobial needs or for use in combination with inorganic antimicrobial agents.
Common types:
Quaternary ammonium salts: good effect on Gram-positive bacteria, strong water solubility, and need to be compatible with coating resins;
Phenols: broad-spectrum antibacterial, but easy to decompose at high temperatures;
Isothiazolinones: high antibacterial efficiency, but poor UV resistance.
2.How to rationally introduce antimicrobial ingredients through coating system design?
Topcoat layer: directly in contact with the outside world, it is the main antibacterial agent
Addition method: mix the antibacterial agent with the topcoat resin, pigment, and solvent, and apply it to the primer surface by roller coating or spraying. The thickness usually accounts for 60%~80% of the total coating.
Key: The antibacterial agent needs to be evenly dispersed to avoid agglomeration.
2. Primer layer: auxiliary antibacterial + enhanced adhesion
The primer is directly combined with the substrate, and a small amount of antibacterial agent can be added to inhibit the growth of microorganisms caused by substrate corrosion, while enhancing adhesion with the topcoat.
3. Varnish layer: protect antibacterial components
For high-demand scenarios, a transparent varnish can be applied on the topcoat surface, which contains antibacterial agents or serves as a protective layer for antibacterial topcoat to reduce the loss of antibacterial components in the bottom layer due to friction and cleaning.
3.How to ensure stable antibacterial performance in antimicrobial agent dispersion process?
Use high-speed shear dispersion or sand milling to disperse the antimicrobial agent particles to the nanometer level to ensure uniform distribution in the coating - uneven dispersion will lead to insufficient local antimicrobial agent concentration and form an "antimicrobial blind zone".
Add dispersant to improve the compatibility of antimicrobial agent and resin and reduce agglomeration.
4.How does the coating curing process ensure stable antibacterial properties?
Curing temperature and time need to match the stability of the antimicrobial agent:
Inorganic antimicrobial agents (such as silver) are resistant to high temperatures (can withstand 250~300℃ curing temperature) and are suitable for high-temperature curing systems such as fluorocarbon and silicon-modified polyester;
Organic antimicrobial agents (such as quaternary ammonium salts) have poor high-temperature resistance (usually ≤180℃) and need to be matched with low-temperature curing resins (such as acrylic resins) to avoid high-temperature decomposition and failure.
Ensure that the coating is fully cured (cross-linking degree ≥90%) and reduce pores (pores will cause the antimicrobial agent to migrate and lose too quickly, reducing durability).
5.How to pre-treat substrates?
Substrates (such as galvanized sheets and cold-rolled sheets) need to be thoroughly degreased and rust-free to prevent residual oil or scale from becoming a "hotbed" for microbial growth (even if the coating is antibacterial, microorganisms on the surface of the substrate may corrode the coating).
For humid scenes, the substrate can be galvanized + passivated (such as chromate passivation) to improve corrosion resistance and reduce the indirect impact of substrate rust on the performance of the antibacterial coating.