Dimensional stability and decay resistance of clay treated, furfurylated, and clay-reinforced furfurylated poplar wood

Plantation-grown poplar (Populus cathayana) is regarded as a source of low-quality wood, with poor dimensional stability and low decay resistance. In this study, poplar wood was impregnated with sodium montmorillonite (Na-MMT) or organo-montmorillonite (O-MMT), furfuryl alcohol (FA, at concentrations of 15%, 30% and 50%), separately or in their combinations to prepare clay treated, furfurylated, and clay-reinforced furfurylated wood, respectively. The two-step method by introducing Na-MMT first and then FA and organic modifier was feasible to achieve a reasonable penetration. These components could entirely enter the wood cell lumen or partly enter the wood cell wall, and thus initiate a series of reactions. Compared with Na-MMT reinforced furfurylated wood (M-F), the O-MMT reinforced furfurylated wood (O-F) exhibited better dimensional stability (ASE up to 71%) and decay resistance (3.2% mass loss). Moreover, O-MMT played a predominant role in decay resistance of O-MMT reinforced furfurylated wood. Even at low O-MMT loadings, the modified wood had a significant inhibitory effect on the white-rot decay fungus Trametes versicolor. Based on an overall evaluation, O-MMT reinforced furfurylated wood seemed to provide an optimal choice for both moist or wet conditions.

CHEMICAL AND STRUCTURAL CHANGES IN POPLAR WOOD UPON STEAM TREATMENT AT CONSTANT TEMPERATURE AND PRESSURE CONDITIONS FOR DIFFERENT TIME INTERVALS

Technology advancement has helped in the development of high-throughput equipment for the analysis of raw material in paper industries. In this research, we have used some advanced techniques to analyze the pore size, structural and chemical changes, and cellulose crystallinity of poplar wood pretreated with steam at constant temperature and pressure conditions for different treatment time. Samples were analyzed by the nitrogen adsorption test, Fourier-transform infrared spectroscopy – attenuated total reflectance (FTIR–ATR), X-ray diffraction (XRD), and field scanning electron microscopy (FE-SEM). Slit-shaped pores were formed, with a diameter of 2.12 nm, after 30 minutes of treatment. FTIR results revealed the degradation of the lignin skeleton through the formation of guaiacyl and syringyl units and deformation in the cellulose and hemicelluloses structure. The crystallinity index (CI) increased upon steam treatment for up to 15 min, but after that, a drop in the CI was observed. The crystallite thickness (d200) increased after 15 min of treatment, due to the rearrangement of cellulose chains. However, a further increase in steam treatment duration to 30 min resulted in a decline of d200, followed by an increase in the cellulose II crystalline region and d020. The steam treatment duration of 15-30 min was found to be a critical time interval, which led to increases in the number of mesopores, CI, d200, and the cellulose II region in the poplar wood.

Effects of P-Coumarate 3-Hydroxylase Downregulation on the Compositional and Structural Characteristics of Lignin and Hemicelluloses in Poplar Wood (Populus alba × Populus glandulosa)

Elucidating the chemical and structural characteristics of hemicelluloses and lignin in the p-coumarate 3-hydroxylase (C3H) down-regulated poplar wood will be beneficial to the upstream gene validation and downstream biomass conversion of this kind of transgenic poplar. Herein, the representative hemicelluloses and lignin with unaltered structures were prepared from control (CK) and C3H down-regulated 84K poplars. Modern analytical techniques, such as 13C NMR, 2D-HSQC NMR, and gel chromatography (GPC), were performed to better delineate the structural changes of hemicelluloses and lignin caused by transgenesis. Results showed that both the hemicelluloses (H-CK and H-C3H) extracted from control and C3H down-regulated poplar wood have a chain backbone of (1→4)-β-D-Xylan with 4-O-Me-α-D-GlcpA as side chain, and the branch degree of the H-C3H is higher than that of H-CK. With regarding to the lignin macromolecules, NMR results demonstrated that the syringyl/guaiacyl (S/G) ratio and dominant substructure β-O-4 linkages in C3H down-regulated poplar were lower than those of control poplar wood. By contrast, native lignin from C3H down-regulated poplar wood exhibited higher contents of p-hydroxybenzoate (PB) and p-hydroxyphenyl (H) units. In short, C3H down-regulation resulted in the chemical and structural changes of the hemicelluloses and lignin in these poplar wood. The identified structures will facilitate the downstream utilization and applications of lignocellulosic materials in the biorefinery strategy. Furthermore, this study could provide some illuminating results for genetic breeding on the improvement of wood properties and efficient utilization of poplar wood.