Manufacture of oriented board using mild steam treatment of plant fiber bundles

This study investigated the effects of mild steam treatment (0.1 MPa for 2 h) of natural bio-based fibers and orientation (0° and 90°) of those fibers in various fiberboards. Ramie bast, pineapple leaf, and sansevieria fiber bundles were used as materials. The composite fiberboards were prepared using phenol-formaldehyde (PF) resin. To investigate the effect of mild steam treatment on wettability, contact angles of PF resin to the fiber were measured. The mechanical properties of the boards were examined as well as their dimensional stability. The contact angle data showed that mild steam treatment was effective in improving the wettability of fibers. Unioriented steam-treated boards showed better performance of internal bond (IB), moduli of rupture (MOR) and elasticity (MOE), thickness swelling (TS), and water absorption (WA) than other boards. Unioriented steam-treated sansevieria board with longitudinal fiber direction showed higher average values of MOR (403 MPa), MOE (39.2 GPa), and IB (1.33 MPa) and lower values of TS (5.15%) and WA (8.68%) than other boards. The differences in the mechanical properties and dimensional stability of boards were found mainly due to the differences in the ratios of fiber fraction of the boards to the density of the fiber bundles.     

Mechanical and physical characterization of sodium hydroxide treated Borassus fruit fibers

In order to improve the properties by chemical modification and to optimize the alkali concentration,we treated Borassus fruit fine fibers with aqueous sodium hydroxide solutions of different concentrations.In each case,the tensile properties of the fibers were determined.The morphology of the untreated and alkali treated fibers was observed using scanning electron microscope.The surface of the fibers became rough on alkali treatment.The tensile properties of the fibers improved on alkali treatment.The fibers attained maximum tensile properties when treated with 15% aqueous sodium hydroxide solution and decreased thereafter.The crystallinity index of the fibers showed a similar trend.The thermal stability of the alkali treated fibers was found to be higher than that of untreated fibers.Further,the char content was maximum for fibers treated with alkali having concentration of 15% and above.The chemical composition indicated that the percentageof α-cellulose was maximum when the fibers were treated with 15% aqueous sodium hydroxide solution and then decreased thereafter thus indicating the beginning of degradation of the fibers at higher concentrations.Thus,the optimum concentration of NaOH was established as 15% for alkali treatment of the Borassus fibers.     

热磨条件对麦秸中密度纤维板性能的影响

在不同的热磨条件下(蒸汽压力为0.4、0.6、0.8、1.0MPa,磨盘转数为2 500r/min和3 000r/min),将麦秸原料分离成纤维,并试制了相应的麦秸中密度纤维板,对比分析了不同的热磨条件对麦秸中密度纤维板的内结合强度、弯曲性能、吸水性能、表面硬度和边部握螺钉力的影响。结果表明,不同的热磨条件下分离得到的麦秸纤维形态存在差异,纤维的强度和形态对麦秸中密度纤维板的物理力学性能影响较大。当蒸汽压力为0.8MPa,磨盘转数为3 000r/min,麦秸中密度纤维板的各项性能得刮改善。     

用红外光谱分析刨花蒸汽处理后成分的变化

用红外光谱法分析了云杉和白桦刨化蒸汽处埋后成分的变化。红外谱图不出了蒸汽处埋后刨花中的半纤维素和羟基比未处理的减少了,这是蒸汽处理改善刨花板尺寸稳定性的主要原因。红外谱图还示出了在同样的蒸汽处理条件下,白桦中半纤维素和羟基的减少程度大于云杉的减少程度,因此蒸汽处理后白桦刨花板尺寸稳定性的改善程度大于云杉刨花板的改善程度。     

超声辅助提取对竹纤维结构和机械性能的影响

文章以超声波辅助提取竹纤维,研究超声波处理以及超声波处理方式（前超声和后超声）对低试剂量条件下提取竹纤维结构和热性能的影响。结果表明：超声波处理应用于低试剂量竹纤维提取,可降低竹纤维胶质含量,改善竹纤维细度和细度均匀性。用后超声辅助提取竹纤维,竹纤维胶质含量可降低13.2%,纤维直径由489±247 μm降至224±52 μm,平均直径降低率达54.2%。超声辅助提取对竹纤维机械性能有一定程度的影响,对竹纤维拉伸强度略有降低,拉伸模量下降明显,断裂伸长率略有提高,机械强度均匀性增加;后超声辅助提取较前超声辅助提取对竹纤维的机械性能降低程度小。经提取工艺,竹纤维结晶度增加,但超声辅助提取竹纤维结晶度又略有下降,未超声竹纤维结晶度为56.50%,后超声竹纤维结晶度为55.89%,前超声竹纤维结晶度为56.25%;傅里叶红外光谱分析表明,竹纤维化学结构变化主要由纤维提取工艺引起,超声处理对纤维结构影响不明显;通过电镜观察,经纤维提取工艺,原竹材结构中被胶质包覆的单纤维形态暴露,单丝状明显,超声辅助提取增加了纤维表面粗糙度,后超声辅助提取单丝分散性增强;总体上,超声辅助提取可促进低试剂量条件下的长竹纤维提取,对纤维细度有明显改善效果,但对纤维结构和机械性能影响不大。     

蒸汽爆破-乙醇蒸煮两步法预处理对麦秆结构的影响

对麦秆采用先蒸汽爆破后乙醇蒸煮的两步法进行预处理,研究预处理对麦秆组分及结构变化的影响。蒸汽爆破过程实验条件选取200 g绝干麦秆,压力1.75 MPa和时间3.5 min。乙醇预处理过程选取80 g蒸汽爆破麦秆(绝干),55%乙醇,两者固液比1∶5(g∶mL),温度170℃、时间30 min。通过高效液相色谱法测定,预处理最终产物组分中半纤维素降低89%左右,木质素降低35%左右。采用红外光谱、纤维形态分布分析及SEM分析对预处理过程中麦秆结构变化情况进行研究,结果表明:蒸汽爆破过程破坏了半纤维素酯键连接且半纤维素降解非常明显,但对纤维素链结构影响和降解作用相对较低;麦秆经过蒸汽爆破预处理后,纤维平均长度明显降低,而平均宽度却显著增加;再经乙醇预处理后纤维平均长度基本保持不变,但平均宽度降低;经两步预处理后麦秆纤维的天然物理结构由紧密到蓬松,纤维束呈松散状态且纤维表面基本无碎片附着物,利于后续加工利用。     

CHEMICAL AND PHYSICAL CHANGES OF STEAM TREATED WOOD CHIP

High dimensional stable particlcboards could be produced by usisng saturatedsteam treated wood chip at elevated pressures.Sample Particleboards were made from woodchip of Birch(Platyphylla).The component changes of steam treated wood chip were analysedby infrared.Infrared spectra demonstrated that the hemicelluloses in steam treated chip wereless than those in untreated chip.This is one of the main reasons why steam treatment could im-prove particlcboard stability.The free radical concentration of steam treated chip surfaces wasanalysed by ESR spectroscopy.The results showed that free radical concentration of treatedchip surface was higher than that of untreated chip surface.The glueyness of chip increased andparticlcboard resin content decreased.     

Superheated steam treatment of rubberwood to enhance its mechanical,physiochemical, and biological properties

ABSTRACT

This research was aimed to investigate mechanical properties, color and cell-wall components changes, and durability of pre-dried rubberwood (Hevea brasiliensis) after superheated steam (SS) treatment. Wood samples were treated at different SS temperatures (140–180°C) for 1–3?h. The highest compression strength parallel-to-grain, hardness and impact strength were found for samples treated at 160°C for 3?h (30.7% higher than untreated), at 150°C for 1?h (26.6% higher than untreated) and at 150°C for 2?h (52.6% higher than untreated), respectively. The surface color became darker after each treatment in comparison with the untreated wood. The number of accessible hydroxyl groups decreased and the relative cellulose crystallinity increased with SS temperature, indicating decreased hygroscopicity of the treated wood. Also, SEM micrographs of wood surface showed consistent decrease in starch particles with treatment temperature. Both decay and termite resistances of treated rubberwood improved with treatment temperature. All the analyzes showed that dried rubberwood treated with SS had some improvements in the mechanical properties, decreased hygroscopicity, and increase resistance to decay.     

Characterization of the morphological,physical, and mechanical properties of seven nonwood plant fiber bundles

The morphological, physical, and mechanical properties of the nonwood plant fiber bundles of ramie, pineapple, sansevieria, kenaf, abaca, sisal, and coconut fiber bundles were investigated. All fibers except those of coconut fiber had noncircular cross-sectional shapes. The crosssectional area of the fiber bundles was evaluated by an improved method using scanning electron microscope images. The coefficient factor defined as the ratio of the cross-sectional area determined by diameter measurement, to the cross-sectional area determined by image analysis was between 0.92 and 0.96 for all fibers. This indicated that the area determined by diameter measurement was available. The densities of the fiber bundles decreased with increasing diameters. The diameters of each fiber species had small variation of around 3.4%-9.8% within a specimen. The tensile strength and Young’s modulus of ramie, pineapple, and sansevieria fiber bundles showed excellent values in comparison with the other fibers. The tensile strength and Young’s modulus showed a decreasing trend with increasing diameter of fiber bundles.     

Effect of steam pretreatment on wood moisture content and characteristics of vacuum drying

The effects of high temperature steam pretreatment on the change in wood moisture content (MC) and characteristics of vacuum drying were investigated in this study. Poplar and manchurian walnut woods were pretreated with high temperature steam at 100°C and 140°C, prior to vacuum drying. A comparison of the characteristics of vacuum drying between steam pretreated wood and untreated wood was carried out. The results show that during steam pretreatment, the MC of wood decreased within a few hours. The reduction of MC varied with the temperature; the higher the temperature, the faster the MC dropped. During the vacuum drying stage, the rates of drying of pretreated samples were higher than those of untreated samples when MC was below the fiber saturation point. Furthermore, the total drying time of samples treated at a steam temperature of 140°C was lower than that of untreated samples. Therefore, a vacuum procedure after steam pretreatment can effectively shorten the drying time when drying wood.     

Effects of fiber length and orientation on elasticity of fiber-reinforced plywood

Short carbon fibers, a reinforced material in wood veneer composites, were used to investigate the effects of fiber length and orientation of fibers on the elasticity of plywood. The technical feasibility, elasticity, and strength of the reinforced plywood with short carbon fiber were evaluated. In a short fiber reinforcement system, the fiber length does not directly influence the reinforcement in Cox's theory when the fiber length exceeded a certain length. When the length of short carbon fiber is beyond 3 mm, the high reinforced result was obtained in the experiment. However, if fiber length was too long, the reinforced result was less owing to the bridge between fibers and the increase of holes. The optimum fiber length must be considered. The orientation of fibers has a strong influence on the reinforcement. Unidirectional, perpendicular, and random orientation displayed different influence on the elasticity. Experimental results were discussed with Cox's method. Reinforced plywood with short carbon fibers in random orientation has a higher shear modulus and bending strength than the controls, in addition to other mechanical properties.     

Effect of alkali treatment on wettability and thermal stability of individual bamboo fibers

The aim of this study is to examine the wettability and thermal properties of individual bamboo fibers after alkali treatment. The individual bamboo fibers were treated by sodium hydroxide (NaOH) solution with varying concentrations (6, 8, 10, 15 and 25%) followed by freeze-drying treatment. The surface analysis of alkali-treated individual bamboo fibers was characterized by atomic force microscope. Water droplet on the individual fiber surface was observed with drop shaper analyzer and the contact angles on fiber surface were also measured. Thermal properties were further studied by thermogravimetric analysis. The results indicated that alkali treatment resulted in the increase in surface roughness of individual bamboo fibers. Alkali treatment with low NaOH concentration could enhance the wettability of treated individual bamboo fibers, and while the wettability was reduced with alkali treatment at high concentration (25%). Thermal analysis revealed that the onset of decomposition and the maximum decomposition were moved to higher temperature after alkali treatment at low NaOH concentrations (6, 8, and 10%), suggesting the improvement in the thermal stability of treated individual bamboo fibers, while the thermal stability was compromised after alkali treatment at higher concentrations (15 and 25%).     

Characteristics of microfibrillated cellulosic fibers and paper sheets from Korean white pine

Microfibrillated cellulosic fibrous product was successfully obtained from Korean white pine (Pinus koraiensis Sieb. et Zucc.) by using two alternative pretreatments (steam and ozone treatments) followed by disk milling (DM). The steam and ozone treatments were effective in extracting some of the hemicelluloses and degrading lignin, respectively, with both types of treatment resulting in the improvement of mechanical fibrillation as a result of loosening of the cell wall structure. The obtained products showed nanoscopic fibrous morphology even though hemicelluloses and lignin components remained. The specific surface area and filtration time were increased using the DM treatment after both treatments, and the values increased further with longer periods of DM. The paper sheets of the fibrillated products after both the alternative treatments had higher tensile properties at the same DM time scale than the sheets of the products obtained without treatment. Tensile strength was further increased by increasing sheet density showing the highest tensile strength and modulus of 125 MPa and 20 GPa, respectively.     

几种禾本科纸浆纤维在造纸法再造烟叶中的应用研究

对几种禾本科纸浆纤维微观结构、质量及其对再造烟叶理化性质的影响进行研究。结果表明:随着片基中纤维比例增加,片基的抗张强度和涂布率提高;在相同的添加比例下,添加稻麦草浆、大麻秆芯NaOH-AQ浆的再造烟叶表面致密、匀整,而添加蔗渣浆、大麻秆芯APMP浆和针叶浆的再造烟叶表面粗糙、孔隙较大;在相同的添加比例下,添加大麻秆芯机械浆、APMP浆、NaOH-AQ浆、稻麦草氧碱浆、蔗渣浆、针叶浆的再造烟叶,总糖、还原糖、钾离子、氯离子、总植物碱和总氮总体均呈下降趋势。     

利用木质剩余物与废纸制备纸浆模塑材料的比较

对三种缓冲材料及利用木质剩余物一次纤维和废纸再生纤维制备纸浆模塑材料工艺过程进行对比。并利用扫描电镜观察热压干燥和真空干燥成型时,木质剩余物一次纤维与废纸再生纤维纤维形态结构的变化。结果表明：木质剩余物一次纤维纤维长度、宽度较废纸再生纤维得均匀,废纸再生纤维纤维表面有所损伤,纤维间的空隙增加,会导致与纤维间结合力有关的抗张强度、耐破强度和耐折强度等物理性能地下降。在生产实践中,要根据包装物的具体情况,选择合适的纸浆模塑原材料。     

Manufacture and properties of ultra-low-density fiberboard

Low-density fiberboards with densities ranging from 0.05 to 0.50g/cm³ were manufactured with steam injection pressing. Bond-type and foam-type isocyanate compound resin adhesives were used separately at 10% and 30% resin content levels. Two types of different-size fibers from softwood were used. Mechanical, dimensional, thermal, and sound insulation properties of the fiberboards were tested. The results are as follows: (1) Bond-type isocyanate adhesive showed higher mechanical and dimensional properties of low-density fiberboards than the foam-type adhesive. (2) Fiberboards produced from small fibers have better mechanical and dimensional properties than those made from large fibers. (3) Thermal conductivity of fiberboards depends more on the board density than on the type of resin or fiber dimension. At a board density lower than 0.2 g/cm³, the thermal conductivity is almost equivalent to those of thermal insulation materials such as polystyrene foam and rock wool, (4) Generally, the sound absorption coefficient of low-density fiberboards tends to increase at higher sound frequency. As the board thickness increases, low-frequency sounds are more readily absorbed by boards.Part of this report was presented at the 46th annual meeting of the Japan Wood Research Society, Kumamoto, April 1996     

Preparation of activated carbon fibers with large specific surface area from softwood acetic acid lignin

Softwood acetic acid lignin (SAL) free from a high-molecular-mass fraction could be spun at 220°C by a spinning machine equipped with an extruder. Although the resulting fibers required thermostabilization, this step could be conducted with a faster heating rate than that for fibers obtained from hardwood acetic acid lignin (HAL). The thermostabilized SAL fibers were converted to activated carbon fibers (ACF) by carbonization in a stream of nitrogen at 1000°C, followed by steam activation at 900°C. At an activation time of 40 min, the SAL-ACF had a larger specific surface area than the corresponding HAL-ACF. When the activation time for SAL carbon fibers was prolonged to 80 min, the adsorption capacities of resulting ACF against iodine and methylene blue were markedly increased, as was the surface area of the ACF. It was found that SAL-ACF had adsorption properties comparable to those of high-performance commercial ACF. Also, it had a tensile strength equal to that of a pitch-derived ACF.Part of this work was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

Mechanical properties of wood in an unstable state due to temperature changes,and analysis of the relevant mechanism IV: effect of chemical components on destabilization of wood

In order to investigate the effects of chemical components and matrix structure on the destabilization of quenched wood, we examined the physical and mechanical properties of steam-treated wood, hemicellulose-extracted wood, and delignified wood, which were treated at different levels. For steam-treated and hemicellulose-extracted wood,the relative relaxation modulus of the quenched sample was lower than that of the respective control sample. For delignified wood, the relative relaxation modulus fell with weight loss and reached a minimum value at a certain weight loss, and subsequently increased significantly. The hygroscopicity of all treated samples changed slightly by steaming, whereas increased with removing the component. More-over, the average volumetric swelling per 1% MC at 100% relative humidity (RH) was less than at 75% RH and 93% RH for component-removed wood. It was clear that a void structure existed. As a result, the destabilization evaluated by the fluidity (1 - E _t/E ₀) of steam-treated wood was influenced by the amount of adsorbed water. For component-removed wood, destabilization increased temporarily at lower weight loss because of nonuniform cohesive structure. At high weight loss, destabilization will decreased because capillary-condensed water gathered in the voids and obstructed the motion of adsorbed water. However, the destabilization of all treated wood changed less than that of chemically modified wood.     

壳聚糖前处理染色木材耐光性的研究

对壳聚糖前处理与未处理（对照）染色木材耐光性的研究表明,山杨等６种壳聚糖处理与未处理木材用同一染料染色并辐射１０小时后,处理材色差均比未处理材低;经壳聚糖前处理与未处理的安息香木才,用四种不同染料染色,染色材耐光性优于未处理材,但随染料种类不同略有差异。     

Investigation on physical and mechanical properties of pulp–plastic composites from bagasse

High-density polyethylene (HDPE), bagasse fibers treated by four pulping processes (AS-AQ (alkaline sulfite anthraquinone), SODA-AQ (soda anthraquinone), MEA (monoethanolamine) and chemical–mechanical pulping (CMP)), three levels of nano-SiO₂ (0, 2, and 5?wt%), and maleic anhydride polyethylene as coupling agent were used to produce pulp–plastic composites (PPCs) by injection molding. The physical and mechanical properties of corresponding composites were evaluated according to ASTM standards. The results showed that compared to untreated bagasse/HDPE composite, the addition of bagasse pulp fibers increased significantly the mechanical properties such as tensile strength and modulus, flexural strength and modulus, and hardness. The chemical pulps-reinforced composites showed better mechanical strengths than that of CMP-reinforced composites, but in some properties, CMP pulp composites have comparable results to the chemical pulp-reinforced composites. Natural fibers (untreated and treated) increased water absorption and thickness swelling of composites compared to pure HDPE. The addition of nano-SiO₂ particles showed both increasing and decreasing trends on physical and mechanical properties ofPPCs.