Improvement of wood against UV weathering and decay by using plant origin substances: Tannin acid and tung oil

In this study, two kinds of plant origin substances, namely tannin acid (TA) and tung oil (TO), were used to treat wood to improve their durability during outdoor applications. For this purpose, southern yellow pine wood was firstly impregnated with TA solution and then immersed in TO at atmospheric pressure. The samples treated with TA or TO alone, as well as untreated wood, were also prepared for comparison. The performance of the different samples during accelerated UV weathering and brown-rot decay tests were evaluated. The results showed that TO imparted wood with excellent color stability against weathering, while samples treated with TA alone experienced more obvious discoloration. The presence of TO built a barrier for the penetration of UV light and water on wood surface. TA acted as a good UV absorber and free-radical scavenger during UV exposure. It also successfully prohibited the colonization of brown-rot fungi (Gloeophyllum trabeum) on wood owing to its strong antioxidation activity. Overall, wood treated with both TA and TO exhibited the best durability during photodegradation and biodeterioration process.