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1.
We investigated morphological changes in wood tissues of sugi (Cryptomeria japonica) resulting from treatment with the ionic liquid 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which dissolves cellulose. Treatment with [C2mim][Cl] caused dissociation and distortion of tracheids in latewood, but not in earlywood. This difference was due to the difference in swelling behavior of the cell wall between earlywood and latewood. Many pit membranes in bordered pits were broken by treatment with [C2mim][Cl]. In addition, some chemical changes in wood components, such as cellulose and lignin, occurred before significant disruption or destruction of the cell wall. Our results show that the reaction of wood liquefaction by [C2mim][Cl] treatment is not homogeneous, both from chemical and morphological viewpoints. 相似文献
2.
Hisashi Miyafuji Kenji Miyata Shiro Saka Fumio Ueda Midori Mori 《Journal of Wood Science》2009,55(3):215-219
Reaction of Japanese beech (Fagus crenata) in an ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, was investigated.
Although both lignin and polysaccharides such as cellulose and hemicelluloses can be liquefied at a treatment temperature
of around 100°C, the liquefaction of polysaccharides mainly occurs at the beginning of the treatment with [C2mim][Cl]. Cellulose
crystallinity in the wood was gradually broken down as the treatment continued. The solubilized polymers were depolymerized
to low molecular weight compounds. The results indicate that [C2mim][Cl] is an effective solvent and reagent for the liquefaction
of wood components and subsequent depolymerization of them.
Part of this report was presented at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, April 2008 相似文献
3.
The morphological changes in wood tissues of Japanese beech (Fagus crenata) upon treatment with the ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, were investigated. Treatment with [C2mim][Cl] induced significant swelling of all wood tissues. However, the swelling behavior of wood fibers was different from that of vessels. Intervascular pits were occluded, and pit membranes in ray-vessel pits were broken after treatment with [C2mim][Cl]. No significant differences in swelling behavior were found between latewood and earlywood, although different morphological changes for latewood and earlywood during [C2mim][Cl] treatment were seen in our previous studies on sugi (Cryptomeria japonica). We have found that the effects of [C2mim][Cl] on Japanese beech tissues are inhomogeneous and different from those found for other wood species. 相似文献
4.
Umi Hamidah Takuya Arakawa Yin Ying H’ng Akiko Nakagawa-izumi Masanori Kishino 《Journal of Wood Science》2018,64(2):149-156
In this work, pretreatment of wood meals using a recycled ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim]Ac), enhanced glucose liberation by enzymatic saccharification, without dissolution of cellulose and lignin. In contrast, previous studies on IL pretreatment have mostly focused on lignocellulosic dissolution to regenerate cellulose and removing lignin. Softwood (Cryptomeria japonica) was pretreated with [Emim]Ac at 60–100 °C for 2–8 h without collecting regenerated cellulose. The pretreatment did not have a strong effect on wood component dissolution (weight of residues: 91.7–98.8%). The residues contained relatively high amounts of lignin (26.6–32.6%) with low adsorption of [Emim]Ac (0.9–2.7%). Meanwhile, the crystallinity index (C r I) of cellulose in the wood was significantly reduced by pretreatment, from 50.9% to 28.4–37.1%. In spite of the high lignin contents in the residues, their glucose liberation values by enzymatic saccharification using a cellulase mixture were 3–16 times greater than that of untreated wood. A good correlation was found between the saccharification effectiveness of pretreated samples and the C r I. Although lignin dissolved in [Emim]Ac continued to accumulate after repeated use of [Emim]Ac, the pretreatment was found to be effective for three consecutive cycles without the need to remove the dissolved materials. 相似文献
5.
Akira Isogai 《Journal of Wood Science》2013,59(6):449-459
Nanocelluloses, which include nanofibrillated celluloses (NFCs) and cellulose nanocrystals (CNCs) with high and low aspect ratios, respectively, are promising new bio-based nanomaterials, prepared from wood and other plant celluloses by mechanical shearing in water with or without pretreatments. Low degrees of enzymatic hydrolysis, carboxymethylation, acetylation, oxidation, and other position-selective modifications on cellulose microfibril surfaces have been applied as pretreatments to wood celluloses to reduce energy consumption in the mechanical shearing process and to improve the nanofibrillation level of the obtained NFCs. NFCs are convertible to nanocellulose sheets, films, hydrogels, foams, and aerogels with fibril network structures or close-packing structures using coating on base films or filtration process like papermaking, which is advantageous for efficient removal of water predominantly present in the NFC/water dispersions. NFC-containing self-standing films, coated films, and NFC/matrix nanocomposites in most cases show explicitly high mechanical strength and ductility despite being lightweight and having optical transparency, thermal stability, and gas-barrier properties. Because NFCs have aspect ratios and molecular weights higher than those of CNCs, the most promising and challenging end products are NFC-containing nanocomposite materials having higher functionalities than those of the conventional fiber-reinforced composite materials. 相似文献
6.
Several ionic liquids promote depolymerization of wood components, i.e., polysaccharides and lignin, into low molecular weight compounds, some of which further re-polymerize into resin-like compounds. In this study, the depolymerization/re-polymerization of wood components in ionic liquids was applied to preparation of plywoods from Japanese cedar (Cryptomeria japonica) veneers by employing ionic liquids as adhesives. The adhesive solution was prepared by mixing an ionic liquid (pyridine hydrochloride ([Py][Cl]), imidazole hydrochloride ([IM][Cl]), or 1-ethylpyridinium chloride ([EtPy][Cl])) with water and d-glucose in various weight ratios. Tensile shear test of the three-ply plywoods prepared from the veneers and the adhesive solution through hot-pressing indicated that the plywood bonded with the [IM][Cl]-based solution ([IM][Cl]/water/glucose ratio: 9/3/2) exhibited the highest strength. Scanning electron microscope observation on the plywoods suggested that the ionic liquids softened the cell walls of the probably plywood through the depolymerization/re-polymerization reactions and the cell walls were compressed during the hot-pressing process. Entwining of the compressed cell walls and van der Waals force enhanced by the compression were considered to be origins of the adhesion of the veneers. 相似文献
7.
The influence of reaction atmosphere on the liquefaction and depolymerization of wood in an ionic liquid, 1-ethyl-3-methylimidazolium
chloride ([C2mim][Cl]), has been systematically studied. The wood samples were treated with [C2mim][Cl] at 120°C under various
atmospheres such as oxygen, nitrogen, and carbon dioxide, both dried and humidified. The percentage of residue after the treatment
shows that oxygen considerably accelerates the liquefaction of wood in [C2mim][Cl], and humidity hardly affects liquefaction
under any atmosphere. Gel permeation chromatography (GPC) and high performance liquid chromatography (HPLC) analyses on the
solubilized compounds in [C2mim][Cl] indicate that oxygen and humidity enhance the depolymerization of the wood component.
Thus, the reaction atmosphere was revealed to influence, and 1be capable of controlling, the reaction of wood in [C2mim][Cl]. 相似文献
8.
To improve interfacial adhesion between wood veneer and high-density polyethylene (HDPE) film, wood veneer was thermally modified in an oven or chemically modified by vinyltrimethoxysilane. The wood veneers were used to prepare plastic-bonded wood composites (PBWC) in a flat-press process using HDPE films as adhesives. The results showed that both modifications reduced veneer hydrophilicity and led to enhancement in shear strength, wood failure, and water resistance of the resulting PBWC. The thermal treatment significantly decreased the storage modulus close to 130 °C (the melting temperature of plastic). Thermal-treated wood veneer maintains mechanical interlocking for bonding and veneer strength which then declined under thermal treatment due to hemicellulose degradation and cellulose de-polymerization. In the silane-treated PBWC, enhanced interlocking and a stronger bonding structure resulted from the reaction between the silane-treated veneer and HDPE. This strong bonding structure allowed thermal stability improvement demonstrated by high modulus and low tanδ values. However, the strength of silane-treated PBWC was still much lower than thermosetting resin-bonded composites at higher temperatures due to the melting behavior of thermoplastic polymer, precluding its use in certain applications. 相似文献
9.
作为合聚俣物复合材料增强的木纤维素包括木纤维素粉和纤维素纤维。本文综述３个方面主要的研究进展；木纤维素粉在热固性塑料中的增强，用偶俣剂涂覆纤维素纤维在热塑性聚合物中的增强以及纤维素纤维在易生物降解聚俣物的增强。简要介绍了三类木纤维素增强复合材料的性质，指出最终的目标是制备符合环保要求完全物降解的复合材料。 相似文献
10.
Three hardwoods of varying vessel arrangement were treated with the ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, to investigate its influence on wood tissue morphology. Characterization was carried out by light and scanning electron microscopy. The wood fibers of all species swelled significantly during [C2mim][Cl] treatment. The swelling behavior varied according to wood species and differed from other cell types such as ray parenchyma cells. Morphological changes of the pits also varied between wood species. Treatment with [C2mim][Cl] affects wood tissues differently depending on wood species and cell type. These differences are not due to the vessel arrangement and its presence, but possibly from the chemical component and the microfibril angle of various wood tissues. 相似文献
11.
Ankita Hazarika 《Wood material science & engineering》2017,12(1):24-39
Wood polymer nanocomposites (WPNCs) based on nano-ZnO and nanoclay were prepared by impregnation of melamine formaldehyde–furfuryl alcohol copolymer, 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU), a cross-linking agent and a renewable polymer obtained as a gum from the plant Moringa oleifera under vacuum condition. Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD) studies were employed for the characterization of modified ZnO and WPNCs. The change in crystallinity index (CrI) value of the cellulose in wood and the distribution of ZnO nanoparticles in composites were determined using FTIR and XRD. Scanning electron microscopy and Transmission electron microscopy showed the presence of nanoparticles and nanoclay in the cell lumen or cell wall of wood. An enhanced UV resistance property was shown by the treated wood samples as judged by lower weight loss, carbonyl index, lignin index, cellulose CrI values, and mechanical property loss compared to the untreated wood samples. Wood polymer composites treated with 3 phr each of nanoclay, ZnO, and the plant gum showed an improvement in mechanical properties, flame-retarding properties, thermal stability, and lower water uptake capacity. 相似文献
12.
Rashmi Kumari Hirokazu Ito Masahiro Takatani Miho Uchiyama Tadashi Okamoto 《Journal of Wood Science》2007,53(6):470-480
Although wood/cellulose-plastic composites (WPC) of low wood/cellulose content have been more accepted worldwide and are promoted
as low-maintenance, high-durability building products, composites containing high wood/cellulose content are not yet developed
on an industrial scale. In this study, flow properties, mechanical properties, and water absorption properties of the compounds
of cellulose microfiber/polypropylene (PP) and maleic anhydride-grafted polypropylene (MAPP) were investigated to understand
effects of the high cellulose content and the dimensions of the cellulose microfiber. The molding processes studied included
compression, injection, and extrusion. It was found that fluidity is not only dependent on resin content but also on the dimension
of the filler; fluidity of the compound declined with increased fiber length with the same resin content. Dispersion of the
composite was monitored by charge-coupled device (CCD) microscope. Increasing the plastic content in the cellulose-plastic
formulation improved the strength of mold in addition to the bond development between resin and filler, and the tangle of
fibers. The processing mode affected the physicomechanical properties of the cellulosic plastic. Compression-molded samples
exhibited the lowest modulus of rupture (MOR) and modulus of elasticity (MOE) and the highest water absorption, while samples
that were injection-molded exhibited the highest MOR (70 MPa) and MOE (7 GPa) and low water absorption (2%). 相似文献
13.
Lignin is a potential precursor for low-cost carbon fiber production, but it is difficult to spin and spool lignin because of its complex and interconnected molecular structure. This disadvantage can be overcome by introducing g-polyacrylonitrile (PAN) to lignin. However, the resulting copolymer is insoluble in common organic solvents. In this study, kraft lignin (KL)-g-polyacrylonitrile copolymers with different KL/PAN proportions were prepared via atom transfer radical polymerization (ATRP) method and their solubility in ionic liquids (ILs) was investigated at different temperatures. 1-Ethyl-3-methylimidazolium acetate ([EMIM]Ac), 1,3-dimethylimidazolium methyl sulfate ([MMIM]MeSO4), 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), and 1-butyl-3-methylimidazolium bromide ([BMIM]Br) were used as the ILs. At all investigated temperatures, the highest solubility of KL-g-PAN was observed in [EMIM]Ac, with the order of [MMIM]MeSO4 > BMIM]Br > [BMIM]Cl. The solubility in BMIM]Br and [BMIM]Cl was remarkably low, reaching values of less than 4 g/Kg. The viscosity and surface tension of the KL-g-PAN/[EMIM]Ac solution increased and decreased, respectively, with increasing amounts of PAN and further by the addition of dimethylformamide (DMF) to the solution. FTIR spectra of KL-g-PAN copolymers before and after dissolution suggested that PAN was partially depolymerized from the copolymer during the dissolution process. 相似文献
14.
本文讨论了木质纤维自身胶合的问题，湿法纤维板是实现自身胶粘的典型例子，提出利用木质纤维原料生成实现自身胶合，以及木质纤维原料表面活化是实现良好先决条件，对木质纤维原料自身胶粘的研究寄予厚望。 相似文献
15.
《Wood material science & engineering》2013,8(3-4):106-117
Abstract One of the major issues in a long-term perspective for the use of wood–plastic composites (WPCs) in outdoor applications is the moisture sensitivity of the wood component and the consequent dimensional instability and susceptibility to biological degradation of the composite. In this work, the effects of using an acetylated wood component and a cellulose ester as matrix on the micromorphology, mechanical performance and moisture uptake of injection-moulded WPCs have been studied. Composites based on unmodified and acetylated wood particles, specially designed with a length-to-width ratio of about 5–7, combined with both cellulose acetate propionate (CAP) and polypropylene (PP) matrices were studied. The size and shape of the wood particles were studied before and after the processing using light microscopy, and the micromorphology of the composites was studied using a newly developed surface preparation technique based on ultraviolet laser irradiation combined with low-vacuum scanning electron microscopy (LV-SEM). The water vapour sorption in the composites and the effect of accelerated weathering were measured using thin samples which were allowed to reach equilibrium moisture content (EMC). The length-to-diameter ratio was only slightly decreased for the acetylated particles after compounding and injection moulding, although both the unmodified and the acetylated particles were smaller in size after the processing steps. The tensile strength was about 40% higher for the composite based on acetylated wood than for the composite with unmodified wood using either CAP or PP as matrix, whereas the notched impact strength of the composite based on acetylated wood was about 20% lower than those of the corresponding unmodified composites. The sorption experiments showed that the EMC was 50% lower in the composites with an acetylated wood component than in the composites with an unmodified wood component. The choice of matrix material strongly affected the moisture absorptivity of the WPC. The composites with CAP as matrix gained moisture more rapidly than the composites with PP as matrix. It was also found that accelerated ageing in a Weather-Ometer® significantly increased the moisture sensitivity of the PP-based composites. 相似文献
16.
Manuel Raul Pelaez-Samaniego Vikram Yadama Eini Lowell Raul Espinoza-Herrera 《Wood Science and Technology》2013,47(6):1285-1319
The objective of this paper is to review the published literature on improving properties of wood composites through thermal pretreatment of wood. Thermal pretreatment has been conducted in moist environments using hot water or steam at temperatures up to 180 and 230 °C, respectively, or in dry environments using inert gases at temperatures up to 240 °C. In these conditions, hemicelluloses are removed, crystallinity index of cellulose is increased, and cellulose degree of polymerization is reduced, while lignin is not considerably affected. Thermally modified wood has been used to manufacture wood–plastic composites, particleboard, oriented strand board, binderless panels, fiberboard, waferboard, and flakeboard. Thermal pretreatment considerably reduced water absorption and thickness swelling of wood composites, which has been attributed mainly to the removal of hemicelluloses. Mechanical properties have been increased or sometimes reduced, depending on the product and the conditions of the pretreatment. Thermal pretreatment has also shown to improve the resistance of composites to decay. 相似文献
17.
辐射化学是研究电离辐射与物质相互作用时产生的化学效应的化学分支学科.木材是一种天然生成的由几种高聚物(纤维素、半纤维素、木质素、抽提物)组成的有机复合体, 不同的高聚物在辐射过程中会产生辐射降解、交联等.文中主要概括了辐射加工的发展、特点、原理、辐射剂量, 并详细阐述了辐射加工在木材科学领域中的应用及进展, 主要包括木材辐射干燥、木塑复合材的辐射制备、射线辐射在木材改性中的应用、木材自由基对木材耐候性及辐射对木材各化学组分的影响; 分析了辐射技术在木材科学领域中的应用与发展趋势. 相似文献
18.
Marcel?Kluge Stefan?Veigel Stefan?Pinkl Ute?Henniges Cordt?Zollfrank Albert?R?ssler Wolfgang?Gindl-Altmutter
Coatings fulfill an important function in providing functionality and service life to wood surfaces. In the present study, the potential of nanocellulosic fillers toward improving waterborne wood coating mechanics is evaluated using free-standing coating films. At 2% filler content, significant improvements in static and dynamic mechanical properties were observed. The extent of these improvements was different depending on whether high-aspect-ratio cellulose nanofibrils of short cellulose nanocrystals were used. Chemical surface modification of cellulose nanofibrils did not provide further improvement. The water–vapor sorption properties of the coating films, which were also evaluated, did not show significant effects due to addition of nanocellulose, while optical transparency slightly decreased. 相似文献
19.
Characterization and acetylation behavior of bamboo pulp 总被引：1，自引：0，他引：1
In the present study, the chemical–physical properties of bamboo pulp prepared with a sequential totally chlorine-free procedure
were analyzed and compared with that of commercial wood pulp by SEM, FTIR, TGA, and X-ray. α-Cellulose content was determined
to be 95%, a little less than that of commercial wood pulp. But the crystallinity of bamboo pulp is lower than wood pulp.
Acetylation activity of bamboo pulp was determined to be higher than that of wood pulp, which was carried out in heterogeneous
media with sulfuric acid as catalyst. The cellulose acetate prepared with bamboo pulp can be quickly dissolved in acetone
without distinct difference with that of cellulose acetate prepared with wood pulp. The results indicate the potential utility
of bamboo as an alternative to wood pulp for cellulose derivate fiber material. 相似文献
20.
The chemical conversion of Japanese beech (Fagus crenata Blume) in water-added supercritical methanol was studied for a wide range of water content using a batch-type reaction vessel to obtain chemicals from lignocellulosics. It was consequently found that addition of water enhanced the decomposition of wood cell wall components; cellulose, hemicelluloses, and lignin. In cases of high water content, however, it resulted in low solubility of lignin-derived products causing an increase in the mass of the residue. The water content was thus optimized to be around 10% (v/v) for the decomposition of wood. Concomitantly, the yields and selectivity of the chemicals from wood could be regulated by the addition of water, especially for the lignin-derived products. As a result, the monomeric compounds of lignin, coniferyl alcohol and sinapyl alcohol, were recovered as their γ-methyl ethers in the presence of water in higher yields than those obtained without addition of water. 相似文献