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Bamboo node is a specialized structure that has great effect on both bamboo growth, physical-mechanical properties, and its utilization. Compact structure and particularly high hardness make bamboo node very difficult for slice specimens preparation. In this study, in order to explore the differences in anatomical characteristics of bamboo nodes' vascular bundles among species, 3D structures of bamboo nodes in four bamboo species (Bambusa emeiensis, Phyllostachys edulis , Pleioblastus amarus , and Bambusa rigida) were reconstructed by the micro-CT technique. The characteristics of vascular bundles were comparatively analyzed based on the CT images. The results showed that the vascular bundle morphology of Pleioblastus amarus and Bambusa rigida changed significantly from node to internode. The areas of fiber cells in the middle part along the radial direction of bamboo culm wall has the largest area (0.204 mm2), followed by the inner part (0.151 mm2) and the outer part (0.072 mm2). The area of transport tissue in the inner part along the radial direction of bamboo culm wall has the largest area (0.046 mm2), followed by the middle part (0.028 mm2) and the outer part (0.002 mm2). The bending vascular bundles in bamboo node can be divided into thick and thin types. The average thickness of the thin bending vascular bundles among the four bamboo species was 125 μm, with the thinnest value of 109 μm. While, the average thickness of thick bending vascular bundles was 265 μm, with the thickest value of 335 μm. The number proportion of thick vascular bundles was 60.8%, 42.5%, 32.9%, and 10.7% for Bambusa rigida , Bambusa emeiensis, Pleioblastus amarus , and Bambusa rigida. This study set up a nondestructive and efficient method for 3D anatomical structure characterization of bamboo node and the variation analysis in bamboo nodes' vascular bundles. • 3D structures of nodes of four bamboo species were successfully reconstructed. • Characteristics of Nodes' vascular bundle were determined based on CT images. • Variation in vascular bundle's characteristics could be evaluated by micro-CT. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers were successfully isolated from bamboo using microwave liquefaction combined with chemical treatment and ultrasonic nanofibrillation processes. The microwave liquefaction could eliminate almost all the lignin in bamboo, resulting in high cellulose content residues within 7 min, and the cellulose enriched residues could be readily purified by subsequent chemical treatments with lower chemical charging and quickly. The results of wet chemistry analyses, SEM images, and FTIR and X-ray spectra indicated the combination of microwave liquefaction and chemical treatment was significantly efficient in removing non-cellulosic compounds. Ultrasonication was used to separate the nanofibrils from the purified residues to extract nanofibers. The TEM images confirmed the presence of elementary fibrils, nano-sized fibril bundles, and aggregated fibril bundles. As evidenced by the TGA analysis, cellulose nanofibers isolated by this novel technique had high thermal stability indicating that the isolated nanofibers could possibly be applied as reinforcing elements in biomaterials. [ABSTRACT FROM AUTHOR]

Applications of eco-friendly soy protein (SP) adhesives in the wood industry are restricted by their poor wet bonding strength and mold resistance. In this study, we noted that epoxy crosslinking agents not only have cross-linking properties, but also antifungal properties and can be used as cross-linkable antifungal agents to simultaneously improve the mold resistance and strength of SP adhesives. In order to develop sustainable and highly active epoxy cross-linkable antifungal agents, biomass-derived oxalic acid (OA) was converted into epoxy oxalic acid (EOA) with two electron-withdrawing ester groups, with 99.93% antifungal activity. The 1% ultra-low amount of EOA (when used as crosslinking agent) was uniformly dispersed in the uncured adhesive, prompting the anti-mold life of the adhesive to increase from 2 to 26 days. After curing, the tighter and more stable cross-linked network structure of the adhesive was constructed by the reaction of low reactive groups such as amide II bonds with ultra-low amounts of EOA, and the dry and wet shear strengths were increased by 49.0% and 139.7%, respectively, compared with pure adhesives. In addition, the anti-mold life of the cured adhesive increased from 4 to more than 30 days under the action of residual EOA. This work demonstrates the novel antifungal effect of epoxy crosslinkers, providing a controllable, green, and sustainable idea for the high-efficient improvement of mold resistance and strength of bio-based adhesives. • Epoxy crosslinkers generally have antifungal properties and can act as antifungal agents. • Epoxy oxalic acid (EOA) exhibited 99.93% antifungal activity, derived from inexpensive bio-based oxalic acid. • Soy protein functional groups cross-linked with EOA to construct a stable cross-linked network structure of the adhesive. • The bonding strength and mold resistance of the adhesive were efficiently enhanced by ultra-low levels of EOA. [ABSTRACT FROM AUTHOR]

In this work, both the bio-polyol and cellulose nanocrystals (CNCs) used to produce high bio-content polyurethane (PU) foams were prepared from microwave liquefaction of rape straw. As high as 40% petro-based polyol was replaced by bio-polyol and the bio-foams containing 40% bio-polyol (PU40) were further reinforced by incorporating 1 to 6% CNCs. GC–MS, 1 H NMR and FTIR observations demonstrated that the bio-polyol is a hydroxyl-rich source consisting of C5, C6 sugars and aromatics. The maximum physico-mechanical performance of bio-foam without CNCs was observed from the bio-foam containing 20% bio-polyol. When further increasing bio-polyol content from 20 to 40%, these properties dramatically decreased. This result was possibly due to the complex polyurethane crosslinking reactions with C5, C6 sugars and aromatics. As compared with reference (PU40), the Young's modulus and compressive stress in the optimal 4% CNCs reinforced bio-foam increased by 590% and 150%, respectively. It was noteworthy that these values were highly superior to those of the petro-based foam. Solid state 13 C NMR and FTIR analysis of CNC reinforced bio-foam evidenced that the hydroxyl-rich structure in CNCs participated in the cross-linking reactions, resulting in an increase of the polyurethane crosslinking density, which contributes to the increased physico-mechanical performance of bio-foam. [ABSTRACT FROM AUTHOR]

In this study, the prepolymers (TYF) were prepared by formaldehyde and l -tyrosine, different amounts of TYF were added to prepare TYF modified urea-formaldehyde adhesives (LUF), and the gel time of resin, formaldehyde emission and wet shear strength of the plywood were tested. This result indicated that the optimal addition amount was 3 wt%, and the formaldehyde emission of plywood decreased by 23% to 0.57 mg/L, and the wet shear strength increased by 47% to 1.47 MPa. The thermal degradation and curing characteristics of urea-formaldehyde (UF) and LUF resins were characterized by thermogravimetric (TG) and differential scanning calorimetry (DSC), and the kinetic parameters were analyzed. The results showed that TYF could reduce the formaldehyde emission and improve the wet shear strength significantly. Moreover, the thermal degradation activation energy (E α) of UF resin was increased, and the thermal stability was enhanced. Although the initial and peak curing temperatures of LUF were higher, but the LUF cured more easily than the UF once the curing temperature was reached. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In this study, diethyl ether extractives were isolated from Phoebe zhennan wood and then added into PLA matrix for the preparation of UV protective films (UV-PF). The results revealed that the diethyl ether extractives had good compatibility with PLA. The prepared UV-PF with the addition of 24 wt% extractives showed complete absorption of UV-C (200–280 nm) and UV-B (280–315 nm) and more than 90% absorption of UV-A (315–400 nm), indicating the addition of extractives into PLA contributed to the super UV resistant ability of the PLA based films. The UV-PF still exhibited excellent UV absorbability after strong UV light irradiation. The differential Scanning Calorimetry (DSC) analysis of the films showed that the UV-PF had relatively low thermal degradation temperature compared to the neat PLA films (PF), while the UV-PF showed stronger tensile strength with comparison to that of the PF. The results on the chemical composition analysis of the diethyl ether extractives revealed that the UV absorbability of the UV-PF may own to the benzene structure, C O bonds, C C bonds in the constituents of the extractives, which all have strong absorption in the near UV-region (200–400 nm). Graphical abstract Diethyl ether extractives were isolated from Phoebe zhennan wood and added into PLA matrix for the preparation of UV protective films. The prepared UV protective films with the addition of 24 wt% extractives showed complete absorption of UV-C and UV-B (280–315 nm) and more than 90% absorption of UV-A (315–400 nm), indicating the addition of extractives into PLA contributed to the super UV resistant ability of the PLA based films. The UV absorbability of the UV protective films may own to the benzene structure, C O bonds, C C bonds in the constituents of the extractives, which all have strong absorption in the near UV-region (200–400 nm). Unlabelled Image [ABSTRACT FROM AUTHOR]

Soy-based adhesives are considered to be a substitute for toxic petroleum-based adhesives in wood industry because of its environmentally-friendly property. However, their application range is limited by the lack of high wet bond strength and high toughness. While it is possible to impart these properties to soy-based adhesives by adding a variety of corresponding modifiers, it is difficult to do so by adding a single modifier. In this work, a multifunctional cross-linking agent dodecanedioic acid diglycidyl ester (DADE) with high reactivity, toughening, and hydrophobic effects was synthesized and incorporated into soy-based adhesive to ameliorate the bonding performance of the adhesives. The reaction process between DADE and protein was confirmed by instrumental analyses. Results revealed that the introduction of 4% DADE increased the wet bond strength of the soy protein adhesive by 140% to 1.57 MPa, whereas the wet bond strength (1.11 MPa) of soybean meal adhesive containing 4% DADE was comparable to that of MUF resin. The micrographs of the fracture surface and the force-distance curves of the shear strength test showed that the toughness of the adhesives was significantly improved by DADE. These improvements were attributed to the long hydrophobic aliphatic chains and highly reactive groups from DADE. This modification method avoided using large amounts of chemical additives. This work may provide an efficient and low-consumption method for producing bio-based adhesives with excellent bonding properties. [Display omitted] • The resulting soy-based adhesive was an environmentally-friendly wood adhesive. • A multifunctional crosslinker with toughening and hydrophobic effects was developed. • The use of DADE avoided the addition of additional hydrophobic and toughening agents. • The strength of the SPD adhesive was higher than that of formaldehyde-based resin. [ABSTRACT FROM AUTHOR]

Dioecious plant species exhibit sexual dimorphism in morphology and physiology under water deficit conditions, but the metabolic and molecular mechanisms underlying such differences are barely explored. In this study, we integrated metabolome and transcriptome analyses of female and male full-sibs of Populus deltoides that featured different drought tolerance in response to moderate and severe water shortage conditions. The results showed that male poplars had higher chlorophyll content and photosynthetic capacity, which result in a better growth performance than female poplars under drought conditions. The metabolome profiling revealed that both the quantification and qualification of differentially expressed metabolites in male poplars were higher than those in females. The transcriptome analysis revealed that the KEGG pathway was enriched in plant hormone signal transduction and carotenoid biosynthesis pathway in both male and female poplars under water deficiency. Moreover, the number of differentially expressed genes (DEGs) that were altered by plant sex was much lower than that by drought treatment. Simultaneously, most of these DEGs were up-regulated in male poplars, especially the key genes that involve in ABA synthetic pathway. The results revealed the metabolic and molecular mechanisms underlying the better ability of drought resistance observed in male poplar plants. • Male poplars grew better than female conspecifics under water deficit condition. • Male poplars enriched higher differentially expressed metabolites than females. • Key genes involved in ABA synthetic and signal pathway were up-regulated more in male poplars. [ABSTRACT FROM AUTHOR]

Different spatial locations provide different external conditions for root decomposition, while species and root order cause obvious differences in root substrate quality. Both differences in internal and external conditions may determine root decomposition rate. We explored the effects of decomposition position, root order, and species differences on root decomposition, and determined the role of manganese (Mn) in root decomposition. We conducted a fine root decomposition experiment using roots from Schima superba , Cleyera japonica, and Eurya loquaiana (separated into orders 1−3, 4−5, and 6) in the litter layer, and at 0−10 cm, 20−30 cm, and 40−50 cm soil depth in a subtropical forest. Root mass and concentration of C, N, P, Mn, condensed tannins and total phenolics were measured during two years of decomposition. Root decomposition rates decreased with increasing soil depth for all root samples. Compared to decomposition at 0−10 cm soil depth, remaining mass (% of initial) declined by 7%–34% in the litter layer and increased by 17%–37% at 40−50 cm soil depth. Lower-order roots had a higher decomposition rate than higher-order roots in the litter layer, but at 40−50 cm soil depth, we observed the opposite. Root litter Mn concentration and remaining mass were negatively correlated during the whole decomposition period including the early, middle, and late stages. Initial root Mn content was negatively correlated with remaining mass after two years of decomposition in the litter layer, and at 20−30 cm, 40−50 cm soil depth. However, no significant relationship between mass remaining and initial root N, P, condensed tannins and total phenolics were observed in the subsoil. Variance partitioning showed that the soil layer contributes significantly to the variance in remaining root mass, C, and Mn, whereas root order group contributed more than the soil layer to remaining root N and P. Our results indicate that soil depth is more important than root order for fine root decomposition rate at a site scale. Relative root decomposition rate between lower- and higher-order roots depends on the decomposition environment. Overall, this study strongly suggests that root Mn concentration (whether in initial or other decomposition stages) was much more consistently correlated with mass remaining than traditional predictors of N, P, condensed tannins, or total phenolics. Root Mn concentration greatly indicates root decomposition rates across soil layers, root orders, and species. Initial root Mn concentration and Mn supply capacity of the decomposition environment jointly control root decomposition rates throughout the decomposition process. • Fine root was decomposed by root order in litter layer, and at different soil depth. • Root Mn content and remaining mass were negatively correlated during decomposition. • Root decomposition rate is more affected by soil depth than root order. • Root Mn content controls root decomposition rates across soil layer and root order. [ABSTRACT FROM AUTHOR]

Sand blasting was proposed as a surface modification approach on the small diameter and thin culm wall bamboo species of Neosinocalamus affinis for the fabrication of laminated bamboo composites. The results revealed that sand blasting modification could almost wipe off the wax and silicons deposited on the green and yellow surfaces by removing or damaging the suberized and siliceous cells, pith membrane, and compact arranged sclereid, resulting in the uncovering of the porous structure. Meanwhile, the surface roughness was also increased by the sand blasting modification, which provided appropriate surface characteristics for resin permeability. The weight loss after sand blasting modification was merely 4.3%, and the internal structure was mostly preserved. Average modulus of rupture, modulus of elasticity, and compressive strength of the laminated bamboo composites fabricated from Neosinocalamus affinis were comparable to previous reported similar products and were higher than those from Phyllostachys pubescens and Phyllostachys bissetii. The findings in this study revealed that sand blasting modification could be used as an efficient and environmentally friendly approach on the high yield production of laminated bamboo composites from small diameter and thin culm wall bamboo species. • Sand blasting was efficient in cleaning up non-lignocellulosic substances on bamboo surfaces. • Laminated bamboo composites with yield of 96% was successfully fabricated. • The composites showed comparable mechanical strength with previously reported products. • Sand blasting surface modification was suitable for small diameter bamboo utilization. [ABSTRACT FROM AUTHOR]

Soy protein-based adhesives are biodegradable and renewable and are widely used in wood based products. However, the application of soy protein (SP) adhesives is also limited by its poor mildew resistance, water resistance and bonding strength, so it is necessary to find ways to promote the comprehensive performance of SP adhesives. In this study, hydroxymethyl l -tyrosine (TYF) synthesized from l -tyrosine and formaldehyde was used to enhance the mildew resistance and bonding strength of the SP adhesive. The results showed that the cross-linking reactions of TYF and SP molecules and the condensation reactions between an appropriate amount of TYF molecules enhanced the force between SP molecules and made the cross-linked structure more stable and compact, resulting in a significant increase in the bonding strength of the SP adhesive modified by TYF. Compared with the plywood prepared by the SPI adhesive, the SP adhesive modified with 6 wt% TYF had the best bonding performance, and its dry and wet shear strength were increased by 49.3% and 110.1%, respectively. In addition, l -tyrosine Schiff base, which had antibacterial, bactericidal and antiviral effects, was produced by dehydration of TYF molecules, so the mildew resistance of SP adhesives modified by TYF was effectively enhanced. [ABSTRACT FROM AUTHOR]

Although soy protein (SP) adhesives have shown great potential in promoting the green and sustainable development of the wood industry, the practical application of SP adhesives is limited by poor performance (bonging strength, mold resistance and water resistance). Cross-linking modification is considered to be the most effective modification method for SP adhesives. In this work, non-antibacterial l -tyrosine (TYR) was treated with epichlorohydrin to graft multiple epoxy groups and transformed into tetraepoxy l -tyrosine (ETY). Interestingly, ETY exhibited obvious antifungal properties with a bacteriostatic rate as high as 98.3%. Adding a low amount (3 wt%) of ETY, the wet shear strength of the modified adhesive was 169.1% higher than that of the pristine SP adhesive, reaching 1.83 MPa. Moreover, in an environment of 28 °C and 80% humidity, both uncured and cured SP adhesives (with 3 wt% ETY) exhibited an anti-mold period of more than 30 days. Therefore, this work reveals that non-antibacterial bio-based materials may be endowed with antibacterial properties through epoxidation and transformed into multifunctional modifiers, and provides a new way for the development of high-strength antibacterial bio-based adhesives. • Non-antibacterial bio-based materials may be endowed with antibacterial properties through epoxidation. • The antibacterial rate of tetraepoxy l -tyrosine is as high as 98.3%. • High performance adhesive modified by low amount of ETY. • The wet shear strength of the adhesive (with 3 wt% ETY) increased by 169.1% to 1.83 MPa. • Modified adhesives (with 3 wt% ETY) showed an anti-mold period of more than 30 days. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fracture toughness of bamboo increased with the water content. • One function of water in bamboo was to soften the cell wall, which increased the plastic deformation of bamboo and impeded the propagation of cracks. • The other function of water in bamboo was to make the fracture surface smooth, which indicates that cracks propagated easily. • These two functions of water also affected the fracture toughness of other materials. Most engineering materials are chosen based on their fracture toughness rather than their strength. However, water molecules in air would interact with these materials and affect their fracture toughness, especially for the biomass materials. Bamboo is an excellent engineering material, and the effect of water content on its fracture toughness was still unknown. Thus, in this study, the effect of water on bamboo's fracture toughness was investigated, and the mechanism behind it was discussed. The results showed that the growth fracture toughness increased by 7.6 J/m2 per 1 % increase of environmental relative humidity. The effect of the water includes both promoting and impeding crack growth. The hydrated amorphous layer in cell wall impeded the propagation of cracks, while the water layer on cell wall promoted the propagation of cracks. The former effect was the stronger one in bamboo, and thus the fracture toughness increased. This competition mechanism stemmed from water was also found useful to explain the fracture properties of other kinds of materials, such as wood, stone, and clay. Therefore, a reasonable hypothesis to explain the mechanism of water content on fracture toughness of bamboo and even other materials was concluded in this study. [ABSTRACT FROM AUTHOR]

This work prepared a double-cross-linked biohybrid aerogel (DCBA) bead biosorbent from waste bamboo paper and chitosan by sequential physical (hydrogen bonding and electrostatic interaction between -COO- and -NH 3 + groups) and chemical (polymerization reaction between -COOH and -NH 2 , dehydration condensation between Si-OH and -OH) cross-linkings. The resulting DCBA bead was applied to remove cationic (Methylene blue, MB) and anionic (Congo red, CR) dyes in both single and binary systems. The MB and CR adsorption capacities of DCBA bead increased with increasing adsorbent dosage, contact time, temperature and initial dye concentration. With increasing solution pH, the MB adsorption capacity increased, while that for CR increased first and then decreased. The maximal adsorption capacities for MB and CR were 653.3 and 559.6 mg/g, respectively, in the single system. The thermodynamic analysis results showed a spontaneous and endothermic adsorption process. DCBA bead had a good stability and reusability with the removal efficiencies of 49.4% and 60.6% for MB and CR, respectively, after five cycles of adsorption-desorption. In the binary system, the adsorption of MB was inhibited by CR, while the removal of CR was enhanced by MB. • DCBA biosorbent was prepared using double cross-linking method. • The DCBA bead exhibited excellent stability and recyclability. • The maximum adsorption capacities of MB was 653.3 mg/g. • The maximum adsorption capacities of CR was 559.6 mg/g. • The adsorption mechanisms in single and binary systems were investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Micro-sized bamboo cells with lignin (4–10 %) were prepared via microwave liquefaction. • Nanocellulose with width less than 10 nm was obtained in TBAA/DMSO system. • Highly transparent films with good UVA (82 %) and UVB (99 %) absorbing were fabricated. Bamboo is a potential resource to produce renewable materials with replacement of plastic. In this study, cellulose-rich bamboo fibers and parenchyma with partial lignin (4–10 %) retained were prepared from microwave liquefaction, thereafter nanocellulose with uniform diameter (less than 10 nm) distribution were obtained by directly dissolving the cellulose-rich bamboo cells in TBAA/DMSO system. By solvent-casting, transparent nanocellulose films with efficient UV-absorbing ability especially the excellent UVA (82 %) and UVB (99 %) absorbing performance were fabricated. The films showed homogeneous network structure and had good tensile strength (15−25 MPa). Changes in cellulose crystallinity structure was observed during the film preparation process. Results also showed that the lignin in the cellulose-rich bamboo could distribute uniformly in the nanocellulose films and had effect on the film formation, UV-absorbing ability and physical-mechanical properties. Overall, microwave liquefaction coupling with TBAA/DMSO dissolving system could be selected as a facile and simple method to produce transparent nanocellulose films with UV-absorbing property. [ABSTRACT FROM AUTHOR]