Properties of gypsum particleboard reinforced with polypropylene fibers

This paper details the influence of the length and content of polypropylene (PP) fibers on the physical and mechanical properties of gypsum particleboard (GPB). The length and amount of PP fibers added had a significant effect on the internal bond strength (IB) and the modulus of rupture (MOR) of GPB. The highest IB value was shown at 9 mm length and 9% content of PP fibers. The MOR was highest when the board was made with PP of 12 mm fiber length and 12% content. Suitable contents of PP fibers were advantageous in that they reinforced the properties of GPB so it achieved high performance. In contrast, a high content of PP fibers reduced the IB, MOR, and modulus of elasticity (MOE) of GPB. The thickness swelling was reduced with an increase in PP length and content. It was concluded that the combination of 12 mm length and 12% content or 3mm length and 9% content was optimum for producing good performance of GPB.Part of this paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

Effects of alkali,mild steam,and chitosan treatments on the properties of pineapple,ramie, and sansevieria fiber bundles

This study focused on the effects of treatments of alkali, mild steam, and chitosan on the surface morphology, fiber texture, and tensile properties of pineapple, ramie, and sansevieria fiber bundles. The fibers were treated with NaOH (2%), mild steam (0.1 MPa), and chitosan solutions (4% and 8%). The properties of these treated fibers were characterized and compared with the untreated fibers. Field emission scanning electron microscopy (FE-SEM) was used to observe the surface morphology of those fibers. X-Ray diffraction (XRD) spectroscopy was used to observe the fiber textures. Tensile properties of the treated and untreated fibers were also recorded. SEM micrographs showed that the surfaces of the NaOH-treated fibers were more damaged than those of the steam-treated fibers. The 4% chitosan solution covered the fiber surface more uniformly than the 8% chitosan solution. The steam-treated fibers had higher values of degree of crystallinity, crystallite orientation factor, and crystallite size than the NaOHtreated fibers. Ramie fiber showed greater mechanical properties than the other fibers. The values of tensile strength, Young’s modulus, and toughness of the steamtreated fibers, which were similar to those of the 4% chitosan-coated fibers, were higher than those for the other treatments.     

栽培措施对短周期工业材材性影响规律的研究

对4种不同栽培措施的日本落叶松、湿地松、马尾松和杉木等多种短周期工业材309株样木的材性进行了全面测试分析研究，结果表明．立地指数大，木材生长率和纤维宽度大．但纤维长度、纤维长宽比、木材基本密度、顺纹抗压强度和抗弯弹性模量减小；立地指数相差两级，木材的年龄宽度、纤维宽度、长度和微纤线角度的差异达到显著或极显著水平栽植密度小，木材的年轮宽度和干缩比增大但纤维长宽比及体积全干缩率减小；栽植密度增大，杉木和昭林6号杨木材的力学强度提高，但尾叶桉和I－69杨降低；不同栽植密度的木材pH值及酸碱总缓冲容量，都是心材大于边材，但木材的脲醛树脂胶凝速度，则是边材快于心材.与未间伐林分的木材比较，随着间伐强度的增大、年轮宽度增大．但纤维长宽比和微纤丝角度减小；间伐强度增大，针叶树村的力学强度降低，阔叶树树则提高．但将强度间伐材（间代40％）与未间伐材比较，结果完全相反；北京杨木材心材的pH值、酸碱缓冲容量及总容量，均随间伐强度的增大而增大，但边材却减小．施肥措施能够增大纤维直径，但将导致纤维长宽比、木材密度和力学强度的降低施肥可以使树木速生，但会降低木材密度和质量，在培育建筑结构材的林分应慎用．     

电磁屏蔽功能胶合板的研究

以镍粉、石墨粉、不锈钢纤维和铜纤维作为导电单元,脲醛树脂为胶黏剂,制备3层落叶松胶合板,研究不同导电单元和涂胶量对板材电磁屏蔽效能(ESE)及胶合强度的影响.结果表明,纯镍粉填充的胶合板的ESE几乎为零;后3种导电单元填充的胶合板ESE分别达到5～10 dB,17～21 dB和6～17 dB;试板的胶合强度除不锈钢纤维添加量为80 g/m2时低于国家标准外,其余条件下均达到或超过国家相关标准要求.     

纤维性质对成纸性能的影响

对纤维的三个基本性质－长度、强度和粗度对纸性的影响进行了综述，着重讨论了对强度性质的影响。     

金属纤维与木单板的复合

为了赋予木基复合材料电磁屏蔽功能,在脲醛树脂胶中加入黄铜纤维和不锈钢纤维作为导电单元,制备三层结构的落叶松复合胶合板,研究金属纤维不同施加量以及涂胶量对木基复合材料电磁屏蔽性能(SE)和胶合强度(ST)的影响.结果表明,除SF25-80外,胶合强度均达到或超过国家标准,涂胶量增大对电磁屏蔽效能有不利影响.在施加黄铜纤维条件下,电磁屏蔽效能为6.34～28.76dB,电磁屏蔽和胶合强度模型均不显著;在施加不锈钢纤维条件下,胶合板的电磁屏蔽效能为13.63～21.14dB,电磁屏蔽模型显著,胶合强度模型不显著.金属纤维的加入一方面有利于导电网链的形成,但另一方面对胶合强度有不利影响,进而不利于胶合板的导电性,电磁屏蔽性能是这两个方面综合作用的结果.     

慈竹竹帘胶合板力学性能研究

采用慈竹为原料制造竹帘胶合板,以三种不同的方式进行组坯,研究组坯方式对慈竹竹帘胶合板纵横方向静曲强度、弹性模量、压缩强度与水平剪切强度的影响。结果表明:组坯方式对胶合板的弹性模量与静曲强度影响较为显著。Ⅲ型板纵向各项力学性能最优,Ⅲ型板横向各项力学性能最弱。Ⅰ型板和Ⅱ型板的静曲强度和弹性模量均达到了汽车车厢用竹篾胶合板的A类标准。三种方式组坯板件的主要力学性能均达到了结构用竹木复合板国家A级标准与混凝土模板用胶合板主要物理力学性能指标。     

Mechanical and physical screw withdrawal properties behavior of agglomerated panels reinforced with coir and pejibaye fibers

The screw withdrawal resistance and the mechanical behavior of agglomerated panels reinforced with coir and pejibaye fibers were evaluated using through and non-through screw withdrawal tests. Widespread commercially materials, such as Pinus solid wood, Medium Density Fiberboard (MDF) and plywood, were also tested in order to compare the behavior and results obtained with the lignocellulosic-reinforced agglomerated panels. Among the conventional materials tested, the highest maximum withdrawal load/thickness ratio was measured in solid wood. Panels reinforced with natural fibers showed lower withdrawal resistance than conventional materials. However, panels reinforced with coir fibers reached about 74% of the maximum strength achieved by MDF samples. Panels reinforced with pejibaye showed the worst mechanical performance. Hybridization between pejibaye and coir fibers resulted, however, in a performance improvement of approximately 50% in the maximum withdrawal load comparing with panels reinforced only with pejibaye fibers. The behavior along screw withdrawal was analyzed and could be split into four different steps. Each of these steps was correlated to the screw withdrawal rate, and also with the interactions between the material and the screw. The mechanisms involved in each step are presented and discussed.     

Z-Directional distribution of fiber orientation of Japanese and western papers determined by confocal laser scanning microscopy

Confocal laser scanning microscopy was applied to visualize inside fibers stained with a fluorescent dye, and the fiber orientation distribution in the thickness direction was determined by image analysis from optically sliced images. Fiber orientation angle and anisotropy were determined by the fast Fourier transform method, which holds advantages over the conventionally applied Hough transform with regard to evaluation of fiber width-weighted contribution and intrafiber segmental contribution. An orthogonally layered Japanese paper handmade by the flow-sheet forming method resulted in a clear change of fiber orientation angle from 0° to 90°. Machine-made wood-containing printing paper showed the highest anisotropy, while copier paper showed a low anisotropy. Thick papers like the wood-free paperboard and recycled packaging board showed that the maximum measured thickness was about 150 μm. The depth limit to detect fluorescence was considered to depend on the apparent density of the paper and the light absorption character of the fibers. Part of this study was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, August 2004     

木荷木材物理力学性质及其加工性能研究

采集浙江各地不同树龄木荷木材,通过系统研究木材解剖性质,主要物理力学性质,刨切、旋切等加工利用适应性等,结果表明:树龄20～25 a是木荷木材密度、干缩性、硬度、抗弯强度、抗弯弱性模量、抗压强度及抗剪强度的一个转折点,其主要物理性质和力学强度指标居国产阔叶树材中等级水平;旋切单板胶合强度超过国家标准规定的技术要求,木荷材完全适合生产胶合板;刨切贴面板的刨切效果和贴面后的性能都较好,综合指标相对较高.     

马占相思的树龄和倍性对纤维性状的影响

近年来关于树龄对木材结构影响的研究越来越多,主要集中于研究年轮代表的树龄对木材结构的影响,并运用于林业的早期选育,但很少涉及纵向树龄和维管组织所反应的树龄（管宁,１９９６;姜笑梅,１９９７;刘元,１９９７;马灵飞,１９９７;Ｆａｈｎ,１９９０;崔克明,１９９２;１９９３;１９９５;１９９７;Ｂａｓｓ,１９８４;曾其蕴,１９９０;Ｄｏｎａｌｄｓｏｎ,１９９６）。马占相思（ＡｃａｃｉａｍａｎｇｉｕｍＷｉｌｌｄ．）是含羞草科（Ｍｉｍｏｓａｃｅａｅ）金合欢属（Ａｃａｃｉａ）中生长较快的一个种（Ｇｏｎｚａ…     

Performance of thermomechanical wood fibers in polypropylene composites

ABSTRACT

Thermomechanical wood fibers, as usually used for medium density fiberboard or cardboard production, feature promising characteristics, like a high aspect ratio, for the utilization in thermoplastic composites. The present study investigates the influence of fiber loading and fiber geometry on the mechanical properties of wood-polypropylene composites in order to confirm the results that were found in a previously published literature review. Composites were compounded at fiber contents from 20 to 60 wt.%, using a co-rotating twin-screw extruder and subsequently injection molded to test specimens. Field emission scanning electron microscopy was carried out to evaluate the fracture morphology of the composites. Fiber length was evaluated using an applying a dynamic image analysis system. Compounding reduced fiber lengths up to 97%. The mechanical properties decreased with increasing fiber content for composites without a coupling agent. Strength properties peaking at a fiber content of 50?wt.% for composites containing MAPP. Tensile strength and flexural strength reached 48.1 and 76.4 MPa, respectively. However, it was found that the processing of these fibers into conventional compounding equipment is still challenging.     

碳纤维增强聚合物 重组竹复合材的弯曲力学性能

重组竹已广泛应用于室内高档装饰、园林景观、室外防腐地板等领域,但重组竹的弹性模量比较小,为钢材的1/7~1/5,应用于建筑领域时难以充分发挥其自身高强度的特性。针对重组竹刚度较小的问题,提出一种重组竹板和碳纤维增强聚合物(CFRP)厚板嵌合粘接的新型重组竹复合材料,采用三点弯曲试验和有限元仿真方法,对CFRP 重组竹复合试件的失效模式、荷载 位移关系、应变曲线、胶层界面剥离影响等进行了研究。结果表明:重组竹试件失效模式是跨中位置处拉伸区域竹纤维断裂,且出现若干水平分层破坏,CFRP 重组竹复合试件的失效模式是CFRP与重组竹层间胶层出现大面积剥离;CFRP 重组竹复合试件的变形过程分为线弹性阶段和界面破坏阶段;CFRP可以明显提高重组竹梁的弹性模量和静曲强度,复合试件弹性模量是重组竹试件的2.33~2.94倍,静曲强度是重组竹试件的1.49~1.58倍;胶层界面剥离是CFRP 重组竹复合试件失效的重要因素,胶层界面剥离对复合试件的应变分布和挠度都有较大影响,完全剥离后试件的挠度是未剥离时的3.09倍。     

Effect of the amount of lignin on tensile properties of single wood fibers

Chemical components are the main factors affecting the mechanical properties of wood fibers. Lignin is one of the main components of wood cell walls and has a critical effect on the mechanical properties of paper pulp and wood fiber based composites. In this study, we carried out tensile tests on single mature latewood tracheids of Chinese fir (Cunninghamia lanciolata (Lamb.) Hook.), using three different delignified treatment methods to obtain different amounts of lignin. We applied single fiber tests to study the effect of the amount of lignin on mechanical tensile properties of single wood fibers at the cellular level. The results show that in their dry state, the modulus of elasticity of single fibers decreased with the reduction in the amount of lignin; even their absolute values were not high. The amount of lignin affects the tensile strength and elongation of single fibers considerably. Tensile strength and elongation of single fibers increase with a reduction in the amount of lignin.     

香叶树人工林木材纤维形态特征的研究

通过对香叶树人工林木材纤维形态的测定表明：香叶树人工林木材在1～3 a间木纤维长度属短;在3～18 a间木纤维长度属中等长度。香叶树人工林木材在1～5 a间木纤维长宽比较小,在6～18 a间木纤维长宽比大于45。     

中山杉单板防腐处理对胶合板性能的影响

以CCA为木材防腐剂,对中山杉单板进行防腐处理,然后热压成胶合板。研究结果表明:中山杉单板经防腐处理后制造的胶合板含水率、密度、胶合强度要略高于未经防腐处理的中山杉胶合板,且含水率与胶合强度均达到I类胶合板要求。单板经防腐处理后的胶合板弹性模量、静曲强度差异不显著。不同方法处理单板对胶合板载药量影响很大,其中满细胞法最高,浸泡法和双真空法相近,涂刷法最低。     

木丝杆定向层积材试制与前景展望

提出木丝杆定向层积材概念,研究以木丝杆为单元制造重组木。采用两种不同规格木丝杆单元和不同铺装方法制作木丝杆定向层积材并进行性能测试,结果表明:增加木丝杆长度有助于提高板材抗弯弹性模量;随机定向铺装的板材抗弯强度优于砖墙式定向铺装。     

纳米CaCO3对木纤维增强生物可降解复合材料力学性能的影响

为探索纳米CaCO₃对增强生物可降解复合材料力学性能的影响,采用混炼、注射成型工艺制备纳米CaCO₃改性木纤维/聚乳酸复合材料,研究了纳米粒子添加量（1wt%,2wt%,3wt%,4wt%）及粒子预处理（偶联剂,硬脂酸,偶联剂-硬脂酸）对材料拉伸性能与冲击性能的影响。随着CaCO₃添加量增加,复合材料力学强度先增大后减小,质量分数2%时材料拉伸强度和冲击强度分别提高8%与20%,粒子的增韧效果明显。预处理不仅能增强木纤维与聚乳酸的结合,也提高了纳米粒子分散性,增强材料整体力学性能。纳米粒子在聚合物基体中的分散性及其与聚合物界面结合是影响材料性能的关键。     

Production and harvest of fibers from Aphandra natalia (Palmae) in Ecuador

Aphandra natalia (Balslev & Henderson) Barfod is native to the western Amazon. It is exploited commercially for its leaf sheath and petiole fibers, which are used for brooms. Data from a 2 year study on production and harvest of fibers in the province of Morona-Santiago in Ecuador shows correlations to exist between the degree of the palm's exposure to light and leaf production, and between exposure to light and petiole length (maximum fiber length), while correlation is absent between exposure to light and fiber load per leaf. A linear relation was found between time and leaf production, with an overall average of 5.5 leaves produced per palm per year. No difference in leaf production of male and female palms was found among palms growing at low light intensities, while among palms in open, light-exposed areas, males were found to produce significantly more leaves than females. An average of 8.5 leaves are cut per palm per harvest, yielding 3.4 kg of fibers, while 6.9 leaves are left untouched. Average harvest time per palm is 33 min. Under optimal conditions (high densities of easy accessible palms), one harvester may harvest and clean about 20 kg of fibers in 1 day, selling at US$1.1 kg⁻¹. One hectare with high, but natural, densities of the palm may produce fibers worth US$460 per year, which can be harvested and prepared in 22 work days. Exploitation of the edible fruits may be combined with fiber extraction if female palms are left to produce fruits, while male palms are exploited for fibers, or if harvest frequency of fibers from female palms is lowered considerably below the average of once every 1.55 years. The exploitation practised in the study area appears sustainable.     

阻燃桉树胶合板的初步研究

以磷酸二氢铵（MAP）溶液为阻燃剂,通过浸泡尾叶桉单板,研究了单板的载药量;以Ⅱ类胶合强度为指标,利用正交试验对常规胶合板生产工艺进行了优选。在此基础上,选取浸泡时间和最优生产工艺试制了阻燃桉树胶合板,并对其Ⅱ类胶合强度和燃烧性能进行了检测。结果表明：不同厚度尾叶桉单板的载药量随浸泡时间的延长呈现相似的增长规律;试验所得常规尾叶桉胶合板最优生产工艺为施胶量210 g.m-2、热压温度130℃、热压时间8 min,该条件下胶合板的Ⅱ类胶合强度达到了2.01 MPa;单板浸泡8h后,单板平均载药量为32.05 kg.m-3,所制得阻燃胶合板氧指数提高了13.9%,炭化长度减少了8.3 mm（26.2%）,阻燃性能明显提高,而胶合强度也达到了Ⅱ类胶合板的国家标准。研究初步证明利用常规桉树胶合板生产工艺生产阻燃桉树胶合板是可行的。