木/麻/PP纤维含量对复合材料性能的影响

采用无纺织气流成型织坯再热压的工艺,研究汽车内饰用木/麻/PP纤维三元复合材料中,3种纤维含量对复合材料性能的影响.研究结果表明,增加PP纤维含量,可以提高复合材料的静曲强度和耐水性;麻纤维含量增加对提高材料的强度影响显著,但耐水性略有下降.当PP纤维含量为40%、麻纤维为30%、木纤维30%时,复合材料的性能较佳.     

Preparation and Characterization of Phenolated Wood Using Sulfuric Acid as a Catalyst I: Liquefaction Behavior of Plantation Wood

Chinese fir (Cunninghamia lanceolata) and poplar (Populus spp.) wood meal were phenolated in the presence of sulfuric acid used as a catalyst. The effects of reaction time and reaction temperature on the wood liquefaction were investigated. The results showed that the reaction temperature had the greater influence on the residue content than reaction time. Additionally, the liquefaction curve for the Chinese fir and Poplar were similar in general.     

Studies on pre-treatment by compression for wood drying III: the reduction of moisture content,the recovery rate,and mechanical properties of wood compressed at different moisture content conditions

As a follow-up report, the pre-treatment by compression for wood drying was systematically studied in terms of the reduction of moisture content (MC), the recovery rate (RR), and mechanical properties of wood compressed at different MC conditions. The results showed that MC after compression on water-saturated wood determined the critical value of MC before compression which were about 84 and 105% at a compression ratio of 60 and 40% for Poplar and Chinese fir, respectively. Beyond the critical value, MC after compression remained constantly at about 84% and decreased slightly from 105% for Poplar and Chinese fir, respectively. The MC reduction decreased with the decrease of MC before compression. The MC reduction was rather effective when the MC before compression was higher than the critical value and was recommended to pre-treat for the effectiveness of MC reduction. In addition, after the recovery, the wood volume and mechanical properties were well retained for the wood compressed at all MC conditions which were above fiber saturation point (FSP) before and after compression. Therefore, the pre-treatment by compression is viable in terms of the RR and mechanical properties at rather broad MC conditions above FSP. Moreover, the compression force needed for treatment was almost same at these MC conditions.     

北美地区杨树木材利用现状与前景

过去20多年, 北美地区的杨树已经从杂草树种转变为产生巨大经济效益的用材林树种, 杨树木材因其具有较高纤维素含量和较低的木质素含量, 适合用作纸浆和纸制品的原料。杨木制浆方法有机械法、化学法、半化学法和化学机械法, 杨木浆可以作为高级纸、纸板、新闻纸和包装纸。杨木牛皮纸浆与针叶材牛皮纸浆混合, 具有良好的成纸性能, 透明度高, 适合制作高级用纸。杨木也是传统的锯材、单板和胶合板工业的原材料, 用来生产锯材、单板、胶合板、木质复合板、包装箱、集装箱、火柴杆和筷子等。最近10年杨木定向刨花板和结构复合板产量显著增加, 利用前景广阔。从资源生产的角度来看, 在改良木材化学组成、纤维质量和自然耐久性等方面进行木材性质改良的转基因杨树研究取得了长足进展。从资源利用角度来看, 高价值的工程复合板和高得率的纸浆和纸产品将会在未来发展中快速增长。     

聚丙烯比例对木塑复合材料性能的影响

通过正交试验,以木材纤维和废旧聚丙烯塑料为原料,异氰酸酯或马来酸酐作偶联剂,压制木材纤维/聚丙烯复合材料,研究聚丙烯(简称PP)用量对木塑复合材料性能的影响。结果表明,聚丙烯比例对复合材料的内结合强度、吸水厚度膨胀率、静曲强度和弹性模量有不同的影响。在热压时间、热压温度、复合材料密度相同的条件下,用异氰酸酯(简称MDI)作偶联剂,聚丙烯用量40%时复合材料的性能最佳;而用马来酸酐(简称MA)作偶联剂,聚丙烯用量50%时复合材料的性能最佳。     

木粉增强P34HB生物复合材料的制备及其结构性能表征

【目的】通过木粉纤维增强生物塑料聚3-羟基丁酸酯-co-4-羟基丁酸酯(P34HB),为生物复合材料的理论研究和生物可降解塑料的广泛应用提供科学依据和理论支持。【方法】以毛白杨木粉和P34HB为原料,采用共混热压法制备P34HB/木粉生物复合材料,基于电子扫描显微镜(SEM)、差示扫描量热法(DSC)、热重分析(TGA)、傅里叶红外光谱(FTIR)、动态热机械分析(DMA)和力学性能分析等手段对其结构和性能进行表征。【结果】随着木粉含量增加,生物复合材料的拉伸强度、断裂伸长率和弯曲强度先增加后减小,冲击强度逐渐下降,拉伸强度、弹性模量和杨氏模量分别增加89%、59%和103%,储能模量E′逐渐增加,tanδ峰值先下降后上升。生物复合材料的高频率模量大于低频率模量,动刚度比静刚度好。相比P34HB,生物复合材料的热分解区间变宽,热解速率变慢,热解剩余质量增加。【结论】随着木粉含量增加,P34HB分子链运动受阻,生物复合材料的储能模量和脆性增大;同时,木粉纤维的成核作用诱导P34HB形成结晶度高、层状结构发达的横晶层,木粉与P34HB之间界面结合力增强,力学性能和热稳定性明显提高。综合考虑,P34HB/木粉生物复合材料的最佳木粉加入量为50%。     

光老化时间对旱柳枝桠材纤维/聚乳酸复合材料性能的影响

采用自然光对比不同纤维含量木纤维/聚乳酸复合材料进行光照老化试验,对比经过不同时间光照后材料的弯曲性能以及拉伸性能的变化,分析光照时间对材料力学性能的影响。结果显示,加入木纤维后,复合材料的弯曲强度和拉伸强度均出现了先下降后上升的趋势,说明加入一定量的木纤维会对复合材料体系起到一定的增强作用;在受到一定时间的自然光照射后,纯聚乳酸材料和木纤维/聚乳酸材料的弯曲性能和拉伸性能均有显著降低,含有木纤维的复合材料强度降低较少。     

木粉加入量对木／塑复合材料性能影响的研究

研究了聚丙烯与木粉以不同比率复合而成的材料的物理力学性能和复合形态特征。结果表明：不同混合比率的聚丙烯与木粉进行复合后所得的复合材料，除冲击强度有所降低外，其它力学性能均比纯聚丙烯的有较大幅度的提高。木粉表面的酯化处理可以改善木塑界面之间的相容性和复合材料的均匀性。在木塑复合过程中木塑之间发生镶嵌现象使木塑之间产生物理结合。     

人工经济林木材性质研究

对重要人工经济林树种核桃、枣木、银杏、板栗、樟树和橡胶等木材解剖、物理力学、化学性质进行研究。结果表明 :核桃、银杏、樟树生长速度较快、材质好 ,是培育经济和用材两用林的优良树种 ,枣木和板栗材质好、生长慢 ,可以选择经济林果用为主、材用为辅的培育方式 ;核桃、橡胶、樟树和银杏的密度和力学强度较大 ,板栗和枣树木材的密度和力学强度很大 ;樟树、银杏和橡胶木材的纤维素含量与杨木接近 ,木质素含量界于杨木和马尾松之间 ,且纤维形态特征符合造纸用材的要求 ,树干和加工剩余物可以用于造纸 ;人工经济林枣木基本密度、核桃木材纤维长度可以通过生长轮年龄来预测 ,且预测效果显著。     

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.     

杨木材性对酚醛树脂浸渍改性材的影响

采用低分子量酚醛树脂对速生杨木进行浸渍处理、干燥定型,使树脂固化制得改性材。试验表明：低分子量酚醛树脂对杨木具有较好的浸注性,改性材的密度和力学强度均有明显的提高,两组试件改性后浸注性和密度相差不大,但前期经过热水处理的试件改性后密度相对均匀,力学强度略好于直接浸渍的试件。杨木自身材性对改性后物理力学性能的影响各不相同,在实际生产中要根据指标的重要性程度选取最佳方案。     

32个杉木无性系木材密度和力学性质的变异*

３２个杉木无性系间，木材密度和抗弯弹性模量、抗弯强度、顺纹抗压强度均有较大差异，无性系内株间亦存在一定差异。木材密度与抗弯弹性模量、抗弯强度、顺纹抗压强度间的相关极显著，相关系数分别为０．３９５７、０．８３６８和０．９０２０；木材密度与生长速度呈负的遗传相关。     

水降解对木纤维/聚乳酸复合材料性能的影响

聚乳酸是一种强度较高的聚酯类材料,其良好的降解性能在保证了其环保优势的同时,也对其物理力学性能产生一定影响。本研究将木纤维/聚乳酸复合材料置于水环境中进行水解处理,然后测试复合材料的力学性能。结果显示,将复合材料放置在水中一段时间后,复合材料的弯曲性能和拉伸性能都显著下降,木纤维含量越高,材料性能下降越明显。这说明水环境使聚乳酸分子链发生了水解反应,使材料性能下降;同时,木纤维的吸水膨胀和干燥收缩也使材料界面薄弱点增加,使材料性能有所下降。     

木纤维PP/PE共混物复合材料的流变和力学性能(英文)

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.     

Dynamic Mechanical Properties of Wood Powder /Polypropylene Composites

The dynamic mechanical properties of wood powder/polypropylene composites with different wood content treated and untreated with the compatibilizer have been studied. It has been found that addition of wood powders and the compatibilizer can both improve the viscoelasticity of composites. Glass transition temperature (Tg) of appropriate wood powder-filled composites decreased. The value for the storage modulus (G') increased gradually with increasing wood powder content. The addition of the compatibilizer made glass transition temperature shift to a higher temperature. DSC (Differential Scanning Calorimetry) results showed that, for pure PP, the addition of the compatibilizer decreased its melting point, and increased its Calorie of Melt at the same time. For the composite with 50 % wood powder treated with the compatibilizer, the melting point was almost unchanged, but its Calorie of Melt decreased.     

人工林杉木和杨树木材物理力学性质的株内变异研究

按照中国国家标准研究杉木和I-214杨树木材的抗弯弹性模量、抗弯强度、顺纹抗压强度和密度,同时按照日本国家标准研究2个树种的顺纹抗剪强度.结果表明:杉木的抗弯强度、顺纹抗压强度和密度由胸高直径处向上呈波浪形增加,抗弯弹性模量则稳定降低,但不同高度间杉木的物理力学性质没有显著差异;近树皮处木材的物理力学性质高于近髓心处木材,并有极显著差异.对于I-214杨树,只有抗弯弹性模量从髓心到树皮逐渐增加,其他的物理力学性质,最小值在从髓心到树皮的过渡区,最大值在近树皮处,从髓心到树皮,杨树的物理力学性质有极显著的差异.杉木和杨树的径面顺纹抗剪强度从髓心到树皮有极显著差异,并且近树皮的高于近髓心的木材,而弦面顺纹抗剪强度从髓心到树皮没有显著差异.木材密度与力学性质有很好的线性相关关系,木材密度是一个很好的力学强度的预测手段.     

淀粉/木粉复合材料的制备与性能研究

以淀粉和木粉为原料,甘油为增塑剂,通过挤出成型制备淀粉/木粉可生物降解复合材料,重点研究淀粉/木粉混合比例对复合材料性能的影响。采用扫描电镜（SEM）、X射线衍射仪（XRD）和热重分析（TGA）对复合材料进行表征,并对复合材料的力学性能和吸水性能进行测试。实验结果表明：木粉的加入破坏热塑性淀粉的连续性,使复合材料的结晶度增大。复合材料的拉伸强度、吸水率和吸水厚度膨胀率随着木粉比例增大逐渐增大,断裂伸长率却逐渐降低。TGA测试结果表明,随着木粉加入比例增大,复合材料的热分解起始温度逐渐降低,但热分解的终止温度逐渐升高,淀粉和木粉两相依赖性逐渐减弱。     

稻壳形态对稻壳--木材复合材料性能的影响

测试了稻壳形态对稻壳-木材复合材料物理力学性能的影响。试验结果表明，以20网日、30网日和40网目的稻壳为补充材料制备的密度为0．80g／cm^3的板的物理力学性能均达到国标二级品的要求。确立20网目的稻壳适宜于稻壳-木材复合材料。     

无机物填充改性复合木材的制备及性能研究

为改善速生杉木木材的性质,试验中先后用硫酸铝和水玻璃等溶液对其进行处理,浸入木材的铝离子与硅酸根离子结合,在木材微纤丝间隙和管胞(或纤维)的胞腔中生成硫酸铝沉淀,从而使木材中填充了大量的无机物,得到杉木无机复合木材.无机复合木材的尺寸稳定性显著提高,在最优化工艺下,复合木材的抗收缩系数可达34.21,稳定系数在80%以上.同时,复合木材除抗冲击韧性略有下降外,其余如抗弯强度、抗弯弹性模量、顺纹抗压强度及硬度等主要力学性能指标均有明显提高.     

聚丙烯比例对木塑复合材料性能的影响

以木材纤维和废旧聚丙烯塑料为原料,异氰酸酯(MDI)或马来酸酐(MA)为偶联剂,压制木材纤维/聚丙烯复合材料;通过正交试验,研究聚丙烯(PP)用量对木塑复合材料性能的影响.结果表明:PP比例对复合材料的内结合强度、吸水厚度膨胀率、静曲强度和弹性模量有不同程度的影响.在热压时间、热压温度、复合材料密度相同的条件下,在用MDI做偶联剂,PP用量为40%时,复合材料的性能最佳;在用MA做偶联剂,PP用量为50%时,复合材料的性能最佳.