Integrated approach for improving mechanical and high-temperature properties of fast-growing poplar wood using lignin-controlled treatment combined with densification.

Previous studies on the modification of fast-growing wood have extensively examined the effects of density and lignin content on the strength and high-temperature properties of modified wood. However, a comprehensive quantitative analysis of their effects on high-temperature performance remains insufficient. To address this knowledge gap, we applied alkali treatment and compression densification to fast-growing poplar, resulting in modified specimens with varying densities and lignin levels. The quantitative effects of density and lignin content on high-temperature properties were meticulously evaluated. Chemical changes were analyzed using Fourier transform infrared spectroscopy (FT-IR), while the mechanical and high-temperature properties were comprehensively assessed. Delignification was found to be positively correlated with treatment duration, with hemicellulose degradation also detected via FT-IR analysis. Significant enhancements were recorded in flexural strength, tensile strength, and modulus of elasticity, accompanied by improvements in ductility ratio and compressive strength. The modified poplar wood exhibited increased thermal stability at elevated temperatures. Furthermore, density and lignin content were identified as significant factors affecting high-temperature performance, establishing minimum density thresholds for various lignin contents in modified poplar wood to ensure optimal performance. This study enhances to the understanding of the intricate relationships among wood properties, modification techniques, and high-temperature performance.

Fire Resistance Improvement of Fast-Growing Poplar Wood Based on Combined Modification Using Resin Impregnation and Compression.

Fast-growing poplar with low wood density has been generally regarded as a low-grade wood species and cannot be used as a building material due to its poor fire resistance. As the fire resistance of wood materials is positively correlated with density, combined treatment using resin impregnation, which imparts thermal resistance, and compression, which improves density, appeared to be a route toward improved combustion performance. Fast-growing poplar wood was modified with a combination of borate-containing phenol-formaldehyde resin impregnation and compression in a transverse direction at varying intensities. The effects of the combined treatment on fire resistance were then examined and discussed. Char residue morphology analysis and microscopic observations were conducted to reveal the effects and mechanism of the combined treatment on fire resistance improvement. The test results showed that fire resistance was greatly improved, including the static and dynamic bending performance at elevated and high temperatures, as well as the combustion performance. The higher the compression ratio was, the better the fire resistance of the modified wood.

Preparation of Transparent Fast-Growing Poplar Veneers with a Superior Optical Performance, Excellent Mechanical Properties, and Thermal Insulation by Acetylation Modification Using a Green Catalyst.

There has been growing interest in transparent conductive substrates due to the prevailing flexible electron devices and the need for sustainable resources. In this study, we demonstrated a transparent fast-growing poplar veneers prepared by acetylated modification, followed by the infiltration of epoxy resin. The work mainly focused on the effect of acetylation treatment using a green catalyst of 4-Dimethylpyridine on the interface of the bulk fast-growing poplar veneer, and the result indicated that the interface hydrophobicity was greatly enhanced due to the higher substitute of acetyl groups; therefore, the interface compatibility between the cell wall and epoxy resin was improved. The obtained transparent fast-growing poplar veneers, hereafter referred to as TADPV, displayed a superior optical performance and flexibility, in which the light transmittance and haze were 90% and 70% at a wavelength of 550 nm, respectively, and the bending radius and bending angle parallel to grain of TADPV were 2 mm and 130°, respectively. Moreover, the tensile strength and tensile modulus of the TADPV were around 102 MPa and 198 MPa, respectively, which is significantly better than those of the plastic substrates used in flexible electron devices. At the same time, the thermal conductivity tests indicated that TADPV has a low coefficient of thermal conductivity of 0.34 Wm-1 K-1, which can completely meet the needs of transparent conductive substrates. Therefore, the obtained TADPV can be used as a candidate for a flexible transparent substrate of electron devices.