Anti-bacterial and Anti-mold Efficiency of ZnO Nanoparticles Present in Melamine-laminated Surfaces of Particleboards

Lamination is one of the most widely used techniques for the surface treatment of wood-based composites such as particleboards, fiberboards, etc. It is usually carried out using decor papers impregnated with amino thermosetting resins, mostly melamine-formaldehyde, urea-formaldehyde, or their mixture. Conventional laminates with non-bioactive surfaces are not able to reduce or stop microbial growth when contaminated with organic substances. In this work, zinc oxide (ZnO) nanoparticles were applied into their surface structure to improve their anti-bacterial and anti-mold properties. Melamine-formaldehyde (MF) resin, for the white decor paper impregnation, was modified with ZnO in amounts of 0.1 wt.%, 0.3 wt.%, 0.6 wt.%, and 1 wt.% and pressed onto particleboards. The presence of ZnO in the melamine-laminated surfaces somewhat improved their resistance to the Gram-positive bacteria Staphylococcus aureus (by 20.7% or 9.5%). However, the improvement was considerable (similar to 65% or 46.8%) against the Gram-negative bacteria Escherichia coli. The presence of ZnO in MF resins increased the anti-mold resistance of the intentionally contaminated laminated surfaces against the microscopic fungi Aspergillus niger and Penicillium brevicompactum at most by approximately 50%. ZnO nanoparticles had none or only a small negative effect on the resistance of the laminated surfaces towards aggressive chemicals and dry heat 180 degrees C, and their abrasion resistance decreased at most by approximately 17%.