Bamboo delignification is a common method for studying its functional value-added applications. In this study, bamboo samples were delignified by treatment with sodium chlorite. The effects of this treatment on the bamboo’s microstructure, surface chemical composition, and pyrolysis behaviour were evaluated. Field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were conducted to evaluate these parameters. The FTIR results demonstrated that the lignin peak decreased or disappeared, and some hemicellulose peaks decreased, indicating that sodium chlorite treatment effectively removed lignin and partly decomposed hemicellulose, although cellulose was less affected. The XPS results showed that, after treatment, the oxygen-to-carbon atomic ratio of delignified bamboo increased from 0.34 to 0.45, indicating a lack of lignin. XRD revealed increased crystallinity in delignified bamboo. Further pyrolysis analysis of treated and untreated bamboo showed that, although the pyrolysis stage of the delignified bamboo did not change, the maximum thermal degradation rate (R_max) and its corresponding temperature (from 353.78 to 315.62 °C) decreased significantly, indicating that the pyrolysis intensity of the bamboo was weakened after delignification. Overall, this study showed that delignified bamboo develops loose surfaces, increased pores, and noticeable fibres, indicating that alkali-treated bamboo has promising application potential due to its novel and specific functionalities.

In this study, a further investigation was carried out on the synthesis mechanism, optimal manufacturing conditions, and curing behavior of a sucrose-ammonium dihydrogen phosphate (SADP) adhesive. The results of ¹³C nuclear magnetic resonance (NMR) spectroscopy confirmed that SADP was composed of 5-hydroxymethylfurfural (5-HMF), deoxyfructosazine (DOF), amino compounds, Schiff base, monosaccharides, and oligosaccharide. The optimal hot-pressing conditions were a hot-pressing temperature of 170 °C, a hot-pressing time of 7 min, and a spread rate of 120 g/m². The wet shear strength of plywood bonded at optimal manufacturing conditions met the requirements of China National Standard (GB/T 9846-2015). Thermal analysis and insoluble mass proportion measurements showed that the main curing behavior of the SADP adhesive occurred at curing temperatures higher than 145 °C, and more than 50% insoluble mass was formed when the heating time was longer than 5 min. Fourier-transform infrared spectroscopy (FT-IR) indicated that cross-linking of the cured adhesive was promoted by prolonging the heating time. In addition, pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) confirmed that the cured SADP adhesive was composed of furan and nitrogen-containing compounds.

Bleaching is a common modification method widely used in the industrialization of wood dyeing. Bleaching can regulate the color of the wood, and it also has great effects on the subsequent wood dyeing properties. In this work, three woods, Ayous, Linden, and Poplar, were processed by using the NaOH/H₂O₂/Na₂SiO₃ bleach pretreatment method. Then, the pretreated wood and untreated wood were stained separately by means of water bath dyeing with three dyestuffs: blue anthraquinone and red and yellow double-azo dyestuffs. The study mainly focused on the effect of the bleach pretreatment on the color control and dyeing properties of the wood by analyzing the color difference, staining rate, and final dyeing rate of the dyed wood. The results were as follows: For the color difference, the L* and h* values showed increasing tends, while the a*, b*, and c* values showed decreasing trends. For the staining rate, Ayous reached an equilibrium staining rate at 3~4 h, but for the others, this was not obvious. For the dyeing rate, red and blue Linden veneers and blue Ayous veneers were similar to the unbleached ones, while the final dyeing rate of the other veneers was less than that of the original wood, and the staining rate of the Ayous red and yellow veneer, Linden yellow veneer, and Poplar veneer was less than that of the original wood. The final dyeing rate of the Ayous red and yellow veneers, Linden yellow veneer, and Poplar red, yellow and blue veneers decreased by 4.54%, 2.91%, 5.45%, 10.75%, 2.66%, and 9.55%, respectively. In general, the bleach pretreatment made the staining color of the material surface uniform. The dyeing rate increased due to the increase of the veneers’ permeability. Thus, the veneers quickly reached the equilibrium staining rate, but the equilibrium staining rate of some test pieces decreased. This work provides scientific support for the dyeing process.

In order to further improve the performance of impregnated paper decorated blockboard (ecological board), high-density fiberboard (HDF) was selected as the equilibrium layer to replace the commonly used poplar veneer. Results showed that the performance of HDF ecological board can be comparable to that of poplar veneer ecological board. It had good appearance quality, and its surface scratch resistance, surface wear resistance, water resistance and mechanical properties met the requirements of National Standard GB/T 34722-2017. The surface cracking resistance of the ecological board prepared with HDF as the equilibrium layer reached the highest level (grade 5), far better than that of the poplar veneer ecological board. This was because HDF was a relatively homogeneous material, and its dry shrinkage in both the transverse direction and along the grain direction was much lower than that of the poplar veneer. This characteristic of HDF made it possible to improve the dimensional stability and bending resistance of blockboard substrates under dry and hot conditions. The formaldehyde emission of the HDF ecological board was higher than that of the poplar veneer ecological board, but it met the formaldehyde emission requirements of indoor materials according to GB 18580-2001.

Purpose: The purpose of this paper is to prepare a water-resistant adhesive (SA) from soy flour (SF) with less water-soluble components. Design/methodology/approach: Defatted SF was suspended and stirred in water. Then, the pH of dispersion was adjusted to a predetermined value (i.e. 8, 9 or 10) by the addition of 2M sodium hydroxide (NaOH) solution. After stirring at a predetermined temperature (25°C, 35°C, 45°C) for different time (1 h, 2 h, 3 h), the 2M hydrochloric acid (HCl) solution was added in a dropwise manner into the dispersion until the pH value was adjusted to 4.5. Then, the dispersion was centrifuged at 6,000 rpm for 2 min. The obtained precipitate with less water-soluble components was used as an adhesive (SA) directly. Findings: SA had a wet strength of 1.02 MPa when used for the fabrication of poplar plywood. Polyvinyl alcohol (PVA) solution was applied to improve the tack of SAs to wood surface and the viscosities of SAs were decreased from 10,200 cP to 4,100 cP at room temperature after the PVA addition. The soy proteins in SAs were not denatured to a large extent according to the differential scanning calorimetry and light microscopy. The remained multilevel structures of soy protein played a positive contribution to the water resistance of SAs, and the bond lines of cured SAs were much more stable than those of the cured SF and soy protein concentrate (SPC). Research limitations/implications: The fluidity and solid content of soy adhesives is much lower than formaldehyde adhesives. Further investigations are needed to improve the fluidity of soy adhesives with high solid contents. Originality/value: Novel water-resistant soy adhesives were provided.