Effects of removal of extractives on the chemical composition and mechanical properties of wood

Abstract

Poplar and pine wood were extracted with water, 1% NaOH (wt%) solution, and benzene:ethanol solution (V1 : V2, 2 : 1) to investigate the governing factors and mechanism by which extractives affect wood structure and mechanical properties. The structure, pore distribution, crystal structure, and mechanical properties of samples were analyzed by Fourier transform infrared spectroscopy (FTIR), adsorption of N2 gas, X-ray diffraction (XRD), and mechanical testing, respectively. The results demonstrated that cellulose, hemicellulose, and lignin were degraded to some extent in the course of the dissolution of the extractives. This degradation had a great influence on the structure and quantity of pores. The extraction treatment did not change the crystallization type of the wood, but it increased the crystallinity of the wood, and the length and width of the crystallization area changed. In addition, the mechanical properties of wood were changed when the content of the extractives was reduced.

Mechanical Properties of Low-Stiffness Out-of-Grade Hybrid Pine—Effects of Knots, Resin and Pith

“…With an average RAR of 0.46 (0.45 median), the resins are on average 0.6% higher (−1.2% median) and 0.4% lower (+3.4% median) than clear bending MOE and strength, respectively. Studies on other species also found little to no difference between the bending performance of wood with and without extractives [35,[46][47][48] with the exception of Garcia-Iruela, et al [35], who reported a 14% higher bending strength for resinous wood. The bending failure behaviour of timber which is initiated by its low-relative-compression properties [49] indicates that an increase in compression properties would increase bending performance.…”

“…With an RAR of 0.58 (0.57 median), resins are on average 0.6% (−2.9% median) higher than the clear samples (Table 2 and Figure 29). Zhao, et al [48] found pine containing extractives was 23% stronger in tension than unextracted pine and they attribute this reduced performance to the reduction in density resulting from the extraction processes. Nevertheless, in their study the extraction processes removed not only extractives but also other components of the cell structure that would affect structural performance.…”