Eucalyptus oil encapsulated within calcium-crosslinked sodium alginate for natural wood preservatives against fungi and termite

Abstract

Eucalyptus oil (EO) has attracted considerable interest as a promising wood preservative due to its antifungal properties, biodegradability, and low toxicity to vertebrates. However, its high volatility limits its application as a wood preservative. To resolve this problem, EO was encapsulated by sodium alginate (SA) crosslinked by calcium ions to achieve its sustainable release and the resulted EO@SA-Ca complex was then used as wood preservative to treat wood in this study. The results indicated that EO@SA-Ca showed better water resistance than EO with SA (EO@SA gel). Ca² ⁺ can cross-link with the carboxyl groups in SA to form a three-dimensional mesh structure wrapping EO. The rubberwood EO@SA-Ca treated achieved an acceptable decay resistance rating and could satisfy the requirements on class I defined in Chinese standard GB/T 13942.1-2009. Compared with the wood untreated, the mass loss reduced from 37.98 % to 8.73 % and 30.44-4.83 %, respectively, after 12 weeks' exposure to white and brown rot fungi under 28 °C and 85 % relative humidity storage conditions. Microstructure analysis proved EO@SA-Ca treatment could protect internal structure of wood. The EO@SA-Ca treated rubberwood also showed significantly improvement on termite resistance. Compared with the wood untreated, the mass loss reduced from 5.72 % to 0.85 %. The results indicate that EO@SA-Ca as a wood preservative showed promising prospect in industry.