Moisture induced stresses in cross laminated timber (CLT) made from hydrothermally modified wood

European Journal of Wood and Wood Products - In the current research work, moisture gradients and moisture induced stresses (MiS) were investigated in cross laminated timber (CLT) bearing...     

Synthesis,Characterization, Speciation,and Biological Studies on Metal Chelates of Carbohydrates with Molecular Docking Investigation

The role of starch aerogel (St-AG) and carboxymethyl cellulose (CMC) as biolgical active compounds, when they subjected for complexation with metal ions, is assessed in this work. The complexation is carried out with palladium(II) and copper(II) ions, in solid state. Different tools of analysis are carried out to characterize and elucidate the structures of these complexes, namely: elemental analysis, IR, thermal analysis, magnetic measurement and molar conductance techniques. All synthesized complexes are formed with 1:2 (metal:ligand) stoichiometry except the case of aerogel starch 1:1 (Pd:starch). All isolated complexes show a satisfactory cytotoxic effect results against colon cancer cell lines HCT11. Additionally, these complexes are screened for their antibacterial activities against two types of Gram positive and negative bacteria. Molecular docking investigation confirmed the cytotoxicity and antibacterial results. Proton–ligands association constants and their complex formation constants with some bivalent metal ions, using potentiometric method show that the complexes formed in solution have a stoichiometry of 1:1 [metal:ligand]. The effects of metal ion, ionic radius, electronegativity and nature of ligand on the formation constants are discussed. The formation constants of the complexes with 3D transition metals followed the order Mn²⁺ < Co²⁺ < Ni²⁺ < Cu²⁺ > Zn²⁺.     

纳米纤维素的疏水改性及应用研究进展

纳米纤维素作为一种性能优越的可再生纳米材料，应用前景极为广阔。然而，由于纳米纤维素结构上富含羟基，使其具有极强的亲水性，严重影响了纳米纤维素的疏水性能，并且在一定程度上限制了其在复合材料领域的应用。综述了纳米纤维素疏水改性的研究进展，从物理吸附、表面化学修饰（甲硅烷化、烷酰化、酯化等）、聚合物接枝共聚3个方面简述了目前应用较为广泛的疏水化改性方法，并对疏水纳米纤维素在包装材料、造纸、水净化等方面的应用现状进行了总结。最后对疏水改性纳米纤维素的未来发展进行了展望，旨在为疏水纳米纤维素的研究和应用提供参考。     

Improving the physical and mechanical properties of particleboards made from urea–glyoxal resin by addition of pMDI

The effect of pMDI on physical and mechanical properties of the particleboards made from urea–glyoxal resin was investigated. The nontoxic and ecofriendly urea–glyoxal (UG) resin was synthesized under weak acid conditions, and its different properties were measured. Then, pMDI at various contents (4, 6 and 8% on resin solids) was added to the UG resin prepared. The thermal and physicochemical properties of the resins prepared as well as their water absorption, flexural properties (flexural modulus and strength) and internal bond (IB) strength of the particleboard panels bonded with them were measured according to standard methods. According to the physicochemical results obtained, the addition of pMDI significantly accelerated the gel time and increased the viscosity and solids content of UG resins. Differential scanning calorimetry indicated that the addition of pMDI decreases the onset and curing temperatures of the UG resin. Physical analysis results of the panels indicated that the particleboards made from UG resins with isocyanate yielded lower water absorption when compared to those bonded with the control UG resins. Based on the findings of this research work, the mechanical properties of particleboard panels bonded with UG resins could be significantly enhanced by the addition of increasing percentages of pMDI. The panels having 8 wt% pMDI exhibited the highest flexural modulus, flexural strength and IB strength value and the lowest water absorption among all the panels prepared.     

Mechanical and thermal properties and microstructural evolution of Ta-doped Nb4AlC3

(Nb_1-xTa_x)₄AlC₃ (x = 0–0.5) ceramics were prepared by the hot press sintering method. The XRD results show that the second phase (Nb_1-xTa_x)C is formed when the Ta content increases to 25 mol%. The SEM micrographs show that (Nb_1-xTa_x)C has a core/rim structure, whose formation mechanism was also investigated. Substituting some Ta for Nb can significantly improve the mechanical properties of Nb₄AlC₃. (Nb_0.75Ta_0.25)₄AlC₃ exhibits an excellent fracture toughness of 8.3 ± 0.3 MPa m^1/2 at room temperature (RT). The highest Young's modulus (349 ± 16 GPa) and Vickers hardness (4.5 ± 0.3 GPa) at RT are exhibited by the (Nb_0.5Ta_0.5)₄AlC₃ sample, which correlate to increases of 18% and 80%, respectively, compared with those of Nb₄AlC₃. The flexural strengths of (Nb_0.5Ta_0.5)₄AlC₃ are 439 ± 18 MPa at RT and 344 ± 22 MPa at 1100 °C, which correlate to increases of 27% and 45%, respectively, compared with those of Nb₄AlC₃. The solid solution of Ta and the formation of (Nb_1-xTa_x)C are beneficial to the strengthening of Nb₄AlC₃. The coefficient of thermal expansion (CTE) increases slightly from 7.08 × 10⁻⁶ K⁻¹ for Nb₄AlC₃ to 7.24 × 10⁻⁶ K⁻¹ for (Nb_0.75Ta_0.25)₄AlC₃ at 25–1400 °C. The thermal conductivity of (Nb_0.75Ta_0.25)₄AlC₃ (28.4–29.8 W/m·K) is higher than that of Nb₄AlC₃ (18.1–21.2 W/m·K) over the whole test range (25–1000 °C). Owing to their excellent mechanical and thermal properties, Ta-doped Nb₄AlC₃ ceramics have good potential as structural materials.     

Nanocellulose-based films and their emerging applications

Extensive research has been directed towards the reinvention of paper for advanced applications. Nanocellulose-based films, a novel class of specialty paper primarily made of nanocellulose, demonstrate an ideal combination of sustainability and enhanced or novel properties. Enormous efforts have been devoted to enhancing these intrinsic properties and/or creating novel functions to expedite and expand the use of these materials in high-end fields such as touchscreen, solar cells, and nanogenerators. We review state-of-the-art advances in nanocellulose-based films and their utilization in several emerging and promising fields. We begin with an introduction of four types of nanocellulose-based films distinguished by their functional material loads (e.g., synthetic macromolecular polymers, 0D, 1D, and 2D nanomaterials), which involves their manufacturing techniques, structure design, properties, novel functions, and underlying principles. Additionally, we summarize the value-added applications of nanocellulose-based films in flexible electronics, energy converting or harvesting devices, and water treatment. Finally, we provide a critical viewpoint on the remaining challenges and future opportunities in this field.     

Effects of typical soybean meal type on the properties of soybean-based adhesive

In order to effectively apply soybean meal for the preparation of water-resistant soybean-based adhesives for plywood, the effects of three typical soybean meal products, namely, low-temperature soybean meal (LM), high-temperature soybean meal (HM), and physical soybean meal (PM), on the properties of soybean-based adhesive were investigated. The results indicated that the number of reactive groups in the three soybean meals followed the order LM > HM > PM, which in turn led to various crosslinking densities when these soybean meals were crosslinked by epichlorohydrin-modified polyamide (EMPA) during the curing process. The LM soybean adhesive had 6.6% higher soaking bond strength and 16.5% higher boiling-dry-boiling bond strength than the HM soybean adhesive, and 19% higher soaking bond strength and 33% higher boiling-dry-boiling bond strength than the PM soybean adhesive, respectively. These three soybean meals could be used to prepare soybean adhesives for interior-use plywood because all plywood panels bonded with their adhesives passed a water-soaking test at 63 °C for 3 h, but only the LM soybean adhesive achieved the desired water resistance for floor-base plywood. Among the three evaluated soybean meals, LM was the most promising raw material for the preparation of soybean-based adhesive because of a greater number of reactive groups, higher crosslinking density, and superior bond strength. Plywood panel bonded with HM soybean adhesive had a water resistance lower than, but very close to, the standard required value (>0.8 MPa) for floor-base plywood.     

七层熔融共挤出石头纸在昆钢的工业化实践

通过制备印刷层、遮盖层、发泡层、增强层母料,再将上述各挤入层的熔融胶状物通过同一模头挤出发泡,经常规三辊压光、冷却、牵引、收卷,即得到七层熔融共挤出石头纸。采用该方法制备的石头纸,挺度好、印刷适应性好,比重低,不透明度高、平滑度好、厚度均匀,各项性能指标符合GB/T22806-2008"白卡纸"的性能指标要求,可用于印制美术印刷品、卡片、名片、包装纸盒等。该制备方法在云南昆钢石头纸环保材料有限得到工业化实践。     

柠条的纤维特性及其双螺杆CMP制浆性能研究

以柠条为原料，分析了其化学组分和纤维形态，并探讨了柠条双螺杆CMP法的制浆工艺以及浆料的纤维形态和成纸的物理性能。研究结果表明：与针、阔叶木相比，柠条原料中纤维素和综纤维素质量分数较低，苯醇抽出物和热水抽出物质量分数较高，柠条纤维长度总体偏短，木质部和皮部的纤维质量平均长度分别为0.621和0.819 mm，还存在部分杂细胞。采用3.5% Na₂SO₃和1.5% NaOH常温预浸12 h、90℃汽蒸1 h后再用双螺杆挤浆机在质量分数35%下进行搓丝，并结合高浓盘磨机磨浆，所得CMP浆得率可达73%。柠条CMP浆基本保持了纤维原有的长度，质量平均长度达0.650 mm，长宽比为32.7，纤维解离较好，但分丝帚化情况不理想，含有部分纤维束和杂细胞。当加拿大游离度为300 mL时，柠条CMP浆成纸的环压强度指数和松厚度较高，分别为8.67（N·m）/g和2.56 cm³/g，抗张指数为19.6（N·m）/g，本色浆白度较高，达50%（ISO）。柠条CMP浆适合配抄瓦楞原纸等包装用纸，漂白后可配抄新闻纸和白板纸。     

A viewpoint on the gastrointestinal fate of cellulose nanocrystals

BackgroundCellulose nanocrystalline (CNC) particles possess unique functional properties such as vastly modifiable surface, considerable mechanical strength and acid resistance, as well as, high aspect ratio. CNCs have received great attention for application in diverse fields of technology including (composite) hydrogels fabrication for the gastric protection and enteral delivery of drugs and nutraceuticals.Scope and approachThe orogastrointestinal digestibility and absorbability of the orally administered CNCs is overviewed in the current article. At first, some surface charge-related characteristics of acid-isolated CNCs are communicated. Then, the biocompatibility and biodegradability of CNCs and CNC-reinforced hydrogels are reviewed, followed by presenting credible digestion and absorption scenarios. Finally, the post-absorption metabolism of CNCs is briefly debated.Key findings and conclusionsBacterial cellulose shows good biocompatibility and hemocompatibility. CNC oxidation provides biologically beneficial impacts; for instance, the TEMPO- and periodate-oxidized CNCs have been shown to regulate some blood metabolic variables and improve the degradability in simulated human blood plasma, respectively. Spherical and carboxyl-bearing cellulose nanoparticles can be isolated through ammonium persulfate digestion. The sphericity of particles results in faster cellular uptake. Negatively-charged CNCs are non-mucoadhesive and thus upon ingestion can penetrate into the buccal and intestinal mucosa. One may augment the absorption of CNCs by targeted receptor-mediated endocytosis. It was postulated that sodium bicarbonate secretion into the duodenum can alter CNCs surface chemistry and influence CNC interaction with gut microbiota.