木材的苯酚及多元醇液化反应机理研究进展

综述了国内外在木材苯酚液化及多元醇液化反应机理研究方面的进展,指出了研究木材液化反应机理的重要性,归纳了今后木材液化反应机理研究的发展趋势。深化木材液化反应机理研究可以揭示木材液化的本质,补充和完善木材液化理论研究体系,也有利于实现液化过程的绿色化、降低液化成本、建立液化工艺与产物性质之间的调控机制、加快木材液化技术应用的产业化进程。     

沙柳及柠条灌木材液化产物的核磁共振谱分析

以苯酚为液化剂、硫酸为催化剂的高温油浴加热下液化沙柳、柠条.采用核磁共振仪分别测试了二者液化产物的结构并进行比较分析,结果显示:沙柳、柠条在酸性条件下液化过程中,同时进行着降解、缩聚反应,液化产物主要生成了β-D-葡萄糖和松柏醇芳香核质子以及愈创木基型木质素结构;从1〖KG-*9〗HNMR图谱看出:沙柳液化物峰面积中所含平均质子的数量要多于柠条液化物,而13CNMR分析中,二者液化物的化学位移位置变化基本一致,只是沙柳液化物的谱线强度要比柠条液化物的谱线强度稍大一些.      

三乙醇胺改性沙柳液化产物/异氰酸酯硬质泡沫材料研究

生物质多元醇液化产物与异氰酸酯等反应可制备硬质聚氨酯泡沫材料,而该类材料存在力学性能低、脆性大等缺点,使其应用领域受到限制.以沙柳多元醇液化产物为原料,与异氰酸酯(MDI)等共聚制备沙柳液化产物/异氰酸酯硬质泡沫材料(RPUF),研究添加不同质量分数交联剂三乙醇胺(TEOA)对RPUF物理力学、化学结构和热学特性的影响...     

5种生物质的微波辅助多元醇液化研究

将杨木、杉木、毛竹、稻草和汉麻杆芯这5种生物质原料在微波辅助多元醇中进行单一液化和混合共液化,研究生物质原料种类对微波辅助多元醇液化行为的影响。结果表明:杨木和杉木容易液化,其次为毛竹和汉麻杆芯,稻草最难被液化;稻草液化产物的羟值最大,杉木液化产物的羟值最小,说明苯/乙醇抽提物和灰分含量对生物质的多元醇液化有显著的抑制作用。由于稻草液化效果不佳,只将杨木、杉木、毛竹和汉麻秆芯4种生物质混合,在液固比值为2.5和3时,混合生物质的共液化率分别为91%和95%,显著高于毛竹和汉麻杆芯的单一液化率;羟值居于4种单一生物质液化产物羟值的中间;混合共液化产物的化学组分与汉麻杆芯液化产物区别明显,表明混合生物质在多元醇共液化过程中存在协同作用,可以促进难于液化的单一生物质的液化反应。     

柞木横纹压缩流变性能

对于柞木(Quercus mongolica),用参数分离法测定其横纹压缩流变参数后表明:弹性变形与恒压应力在很大的范围内成直线关系,瞬间塑性变形与恒压应力成为几个阶段的直线关系;推迟弹性及依赖于时间的塑性都遵循以对数为主体的函数,由弹性及推迟弹性合成的粘弹性具有很好的线性特征。以上研究结果与白杨试验所得结果几乎一致。因此,柞木与白杨之间的横纹压缩流变性能并无质的不同,仅仅表现出量的差别。白杨与柞木之比:弹性柔量为2.4～3.4:1;推迟弹性柔量为1.8～2.7:1;临界应力为1:2。     

沙柳苯酚液化产物制备酚醛树脂工艺研究

为了开辟沙生灌木利用的新途径,以沙柳苯酚液化产物为对象,进行液化产物树脂化试验,根据拉伸剪切强度的正交试验和单因素试验确定合适的工艺为甲醛与液化产物的摩尔比为1.5,合成温度75℃,氢氧化钠与液化产物的摩尔比为0.5;红外分析表明,液化产物树脂的官能团比酚醛树脂具有更高的反应活性.     

木粉及其组分的多元醇酸催化热化学液化

分别将木粉、纤维素和木质素在乙二醇中进行热化学液化。研究结果表明木粉中纤维素的非结晶区、木质素和半纤维素首先被液化,而纤维素的结晶区较慢被液化,到液化反应中期基本降解完全,液化产率高于97%。利用在线红外光谱仪跟踪检测了整个液化反应过程,结合GC-MS结果发现:乙二醇在反应过程中脱水生成了二甘醇和三甘醇。在液化反应中,纤维素的糖苷键断裂后生成葡萄糖苷结构,随后葡萄糖苷中的吡喃环也被打开,生成的活性中间体相互反应或与乙二醇反应生成了如3-(2-甲基-[1,3]-二氧戊环-2-基)-丙酸乙酯、乙酰丙酸丁酯等酯类;木质素的苯丙烷结构主要降解为苯酚、2,6-甲氧基苯酚等芳香族衍生物,因此木粉液化产物是聚醚/酯混合多元醇。     

木材液化产物制备热塑性树脂的研究

在酸性催化剂作用下,用木材的苯酚液化产物和甲醛进一步树脂化制备了液化木基热塑性酚醛树脂(PWF).用正交试验方法研究了各影响因素对树脂产率和软化点的影响,结果表明,pH值和反应温度对PWF树脂产率的影响最大,而甲醛与苯酚的投料比对PWF树脂软化点的影响最大.当木材液化产物中残留的苯酚与甲醛的物质的量之比为1∶0.75,pH值为木材液化产物的实际值,在105℃反应150min时,液化木基热塑性酚醛树脂的产率达到124%,软化点为110℃左右.用凝胶渗透色谱(GPC)、傅立叶红外光谱(FT-IR)和核磁共振(NMR)对比研究了PWF和传统热塑性酚醛树脂(PF)的结构特征.结果显示PWF和PF的结构基本相似,酚单元之间的连接形式主要是邻-对位和对-对位连接.PWF中含有木材组分的液化碎片,且相对分子质量较低,分布较窄.     

木材苯酚液化产物制备碳纤维的初步探讨

为拓宽木材液化产物的应用领域,提高木材产品的附加值,实现木材的高效利用,在研究木材苯酚液化产物特性的基础上,提出了木材苯酚液化产物碳纤维材料的制备构思和工艺路线。利用木材苯酚液化产物为前驱体,通过加入反应剂如六次甲基四胺等调制纺丝液,熔融纺丝后将纤丝在甲醛和盐酸混合溶液中加热固化形成网状交联结构,然后在惰性气体保护下高温炭化制备成碳纤维,同时对制备过程中可能存在的影响因素进行了分析。     

杉木间伐材低浓纸浆流变特性

对不同浓度、温度、打浆度、剪切速率对低浓杉木间伐材机械浆流变特性的影响进行了实验研究,并对不同因素引起浆料表观粘度变化的机理进行了分析。结果表明:浆料浓度、打浆度、温度及剪切速率都会对浆料的表观粘度产生影响。随着浆料浓度的增加,浆料表观粘度呈指数式增加;随温度的升高,浆料表观粘度则缓慢下降;打浆度影响浆料的微观结构,随着打浆度的升高,纸浆的表观粘度呈下降趋势;低浓纸浆的表观粘度则随剪切速率提高而递减。在实验测量范围内,杉木间伐材低浓纸浆为满足幂律关系的非牛顿流体,拟合的本构方程的流变特性指数n<1,因此其在测量范围内为假塑性流体。低浓纸浆流变特性的研究纸浆模塑生产线流送系统设计提供了依据。图12表2参16。     

Separation of liquefied product of Salix psammophila by column chromatography and structure analysis of its components

The liquefied product of Salix psammophila wood was separated by thin-layer chromatography (TLC) and column chro-matography, and its structure was identified by nuclear magnetic resonance (NMR) spectra in our study. The separation result indi-cates that the sample of liquefied S. psammophila contained at least two categories of components. The structure of the main compo-nents was guaiacyl C-1, C-2 of the hydroxyphenyl propane, i.e., the aromatic nucleus protons of lignin. Degradation and polycon-densation reactions occurred when the S. psammophila wood was liquefied in phenol. Polycondensation reactions occurred among the depolymerization products from cellulose, the aromatic depolymerization products from lignin and the products of the displace-ment reactions between phenoxide ion and cellulose.     

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.     

壳聚糖对竹溶解浆溶液流变性能的影响

采用浓度为84.2%的N-甲基吗啉-N-氧化物(NMMO)水溶液为溶剂,设计竹溶解浆(BP)-壳聚糖(CS)不同质量分数,依次加入CS粉末和BP,BP充分溶解后制备BP与CS不同质量比的共混溶液。研究了CS对NMMO溶解BP溶液的稳态和动态流变性能。研究表明:在NMMO溶解体系中,BP-CS共混溶液为剪切稀化的假塑性流体,在持续摇振过程中,随着溶液温度(θ)升高,溶液的储能模量(G′)和损耗模量(G″)、复数黏度(η*)均下降,加入适量的CS(CS∶BP=1∶10)可有效阻碍BP大分子不同链间即时物理交联位点的形成,从而改善NMMO溶解BP溶液的流变性能,但是,随着CS添加量的增大,CS与BP大分子链间的相互作用增加又导致了溶液的流变性能降低。     

The effect of number of joints on bending properties of laminated lumber made from poplar (Populus nigra)

Connection plays an important role in structural components and end jointing is one of the most common connections in structural applications.This study was designed to investigate some mechanical properties (MOE and MOR) of solid wood samples manufactured from poplar (Populus nigra),joined together through end jointing.As well,we studied combinations of lumber manufactured from 10-mm veneer,using a polyvinyl acetate adhesive.The results show that non-jointed lumber (control samples) have better bending properties (MOE and MOR) than jointed specimens and lumber made from laminated layers.On the whole,side-byside joints have a negative effect on the MOR and MOE of laminated products,which is more pronounced in the MOR.By increasing the number of joints,the properties of combination of three-ply,i.e.,bending strength and modulus of elasticity,decreased.     

The role of vascular bundles on the mechanical properties of coconut palm wood

This study examines certain physical, mechanical, and anatomical characteristics of coconut palm wood. The results show a correlation between the anatomical characteristics and density as well as lengthwise compression. All properties (density, frequency of vascular bundles (VBs), and mechanical properties) increase with the transverse distance from the center of the trunk. The study also tests VBs from different radial sections of the coconut palm tree (Cocos nucifera) for diameter, ultimate tensile strength, and modulus of elasticity. The influence of the VBs on the overall properties of the wood is discussed.     

马尾松半同胞子代材性遗传变异分析

以贵州省都匀种子园子代测定林的28个半同胞家系的木材样品为材料进行子代测定,研究其基本密度和纤维长和宽等材质性状以及灰分、1%Na OH抽提物、纤维素、综纤维、木质素等5种木材化学组分的遗传变异规律。结果表明:化学组分中除木质素含量外,其他平均值均高于对照组。灰分含量和木质素含量在家系间差异极显著。化学组分中除木质素和灰分外,1%Na OH抽提物、纤维素、综纤维的遗传力均在0.1801~0.2931之间,均小于0.5,说明其均受中等强度以下的遗传控制。通过对半同胞家系主要材性性状聚类分析,选择出8个优良的纸浆材家系。     

The effect of compression and incision on wood veneer and plywood physical and mechanical properties

ABSTRACT

Drying takes the largest share of energy in plywood production, and varying moisture content of veneers necessitates re-drying that often leads to over-dry veneers with deactivated surfaces, which may promote imperfect bonding. In order to decrease the drying time, reduce the need for re-drying of veneers, and improve the quality of plywood, birch and spruce veneers were subjected to pre-treatment by cold compression, incision, or a combination of the two. The effects of pre-treatment on the veneer and plywood quality were assessed by standard tests. Compression had a beneficial effect on water removal of the wettest veneers (spruce sapwood (SW) and birch), but some thickness reduction was observed in the veneers as well as the finished birch plywood. Compression led to thickness reduction of spruce veneers, but had no effect on SW plywood thickness likely due to higher viscoelasticity. Both compression and the combination of incising and compression levelled the moisture variation within the compressed stacks. Incision improved the modulus of elasticity of birch plywood, shear strength of SW plywood, and both bending and shear strengths of heartwood plywood. Higher surface pressure decreased the drying time of spruce SW in both plain compression and combined incision and compression pre-treatment.     

速生材增强处理技术研究进展及发展趋势

本文阐述了人工林速生材木材增强处理的机理、方法和国内外研究进展,分析了木材增强处理技术在产业化应用中存在的问题和未来发展趋势。     

6种江西常见速生阔叶材纤维形态及材性比较

为发展和科学利用速生阔叶工业用材种,对6种江西常见速生阔叶树木荷、苦楝、鹅掌楸、深山含笑、东京野茉莉及檫树的纤维形态及材性进行测定与分析。结果表明：木荷、苦楝、深山含笑、东京野茉莉的纤维都属长细型纤维,具有良好的制浆造纸性能,尤其苦楝属制浆造纸优等材,纤维长度最长,平均纤维长度达1.43 mm。檫树和鹅掌楸制浆造纸性能略差。11～12年生木荷和檫树密度已达中等密度木材范围,其中木荷平均密度最大,平均密度为0.69 g/cm3,但干缩性相对略大,深山含笑尺寸稳定性相对较好;木荷的综合强度最高,抗压强度50.52 MPa,属中级,抗弯强度和抗弯弹性模量分别为141.7 MPa、17.88 GPa,均属高等水平;鹅掌楸综合强度中等,顺纹抗压强度为50.52 MPa、抗弯强度84.99 MPa,抗弯弹性模量14.55 GPa;深山含笑抗弯强度和抗弯弹性模量均可达中等水平,但抗压强度略差;苦楝、东京野茉莉在材性综合强度方面稍差,抗压强度、抗弯强度和抗弯弹性模量方面均属低等水平。