Testing the durability of copper based preservative treated bamboos in ground-contact for six years

In this study, durability of bamboo samples in terms of the variability of location along culm height (top, middle and bottom) were evaluated in a ground-contact feld test for six years in comparison to Scots pine and beech wood samples. Bamboo and wood samples were treated with Wolmanit-CB (CCB) and Tanalith-E (Tan-E) solutions, and then were installed in a feld located in the North-West of Turkey. The decay resistance of samples was assessed by weight loss, and compared by SEM observations and FTIR analysis. Furthermore, chemical leaching from the samples was detected by ICP-OES after the test. Results showed that un-treated bamboo and wood samples had a very low durability such that weight losses were found as 64–80% for bamboo and 57–63% for wood samples. The SEM micrographs showed the characteristics decay patterns of soft-rot type I and brown-rot fungi in the parenchyma cells, vessels and fbers in vascular bundles. Fungal hyphae within the cell walls resulted in the gradual breakdown of the cell wall layers. FTIR analysis revealed the mechanism of the biodegradation, which indicates the reduction of carbohydrate content. The weight loss in CCB and Tan-E treated bamboo samples was reduced as 20–45% depending on bamboo height parts, but the wood preservatives did not ensure suffcient resistance for six years against soil degrading organisms since more than half of the chemical amount leached out from the bamboos to soil. Weight losses were well confrmed by chemical leaching rates for both CCB and Tan-E. It was observed that the lower parts of the culm were more durable, which was also in accordance with ICP-OES and SEM analysis. Copper-based preservatives seemed to be more efcient in pine and beech wood samples than bamboos since the impregnability of bamboo was much lower than that of wood

Flavonoid Insertion into Cell Walls Improves Wood Properties

Wood has an excellent mechanical performance, but wider utilization of this renewable resource as an engineering material is limited by unfavorable properties such as low dimensional stability upon moisture changes and a low durability. However, some wood species are known to produce a wood of higher quality by inserting mainly phenolic substances in the already formed cell walls – a process so-called heartwood formation. In the present study, we used the heartwood formation in black locust (<i>Robinia pseudoacacia</i>) as a source of bioinspiration and transferred principles of the modification in order to improve spruce wood properties (<i>Picea abies</i>) by a chemical treatment with commercially available flavonoids. We were able to effectively insert hydrophobic flavonoids in the cell wall after a tosylation treatment for activation. The chemical treatment reduced the water uptake of the wood cell walls and increased the dimensional stability of the bulk spruce wood. Further analysis of the chemical interaction of the flavonoid with the structural cell wall components revealed the basic principle of this bioinspired modification. Contrary to established modification treatments, which mainly address the hydroxyl groups of the carbohydrates with hydrophilic substances, the hydrophobic flavonoids are effective by a physical bulking in the cell wall most probably stabilized by π–π interactions. A biomimetic transfer of the underlying principle may lead to alternative cell wall modification procedures and improve the performance of wood as an engineering material