Use of pomegranate peel extract for preparation of UV-absorbing and antimicrobial nitrocellulose coating for wood finishing

Antimicrobial and UV-resistant coatings are important finishing materials for making specialty wood products. In the current work, anti-bacterial and UV-resistant coatings were prepared from nitrocellulose (NC) and pomegranate peel extract (PGE). Different ratios of PGE were added to NC solution (up to 10 wt.% of NC) and the effect of PGE on the viscosity of NC solution, optical, UV-absorption, mechanical, moisture sorption, and antibacterial properties of NC films was studied. Finally, the NC/PGE solution with the appropriate antibacterial activity was sprayed onto the surface of beechwood and its surface was evaluated and compared to neat NC coating regarding gloss, color, change in color due to daylight and thermal aging, and wettability by water. The results showed that PGE reduced the viscosity of NC solution even at low concentrations. All the NC/PGE films had good homogeneity, transparency, UV light absorption, film flexibility, and good antibacterial properties against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria at PGE content 6% or higher. PGE moderately increased the moisture sorption of NC films at high relative humidity (98%). Beechwood was sprayed with NC/8% PGE solution in ethyl acetate; the presence of PGE in NC didn’t affect the visual appearance or light indices (L, a, and b) of the coated wood when compared to the coating with neat NC. The NC/8%PGE coating had high stability against daylight aging while there was no difference in color change between the wood coated with NC and NC/8%PGE after thermal aging. The study showed the potential of PGE as a renewable and safe anti-bacterial and UV-resistant additive for nitrocellulose lacquers used in furniture.

Graphical abstract