软木粒子特性与应用研究进展

介绍了软木粒子制备过程、形貌特征和主要物理特性,同时针对软木粒子的应用如自聚结软木、软木粒子复合材料、软木粒子吸附及填充应用等对国内外研究进展进行了综述。基于此,对国内软木粒子的加工、应用及研发提出建议,为我国软木行业的可持续发展提供参考。     

栓皮栎软木动态黏弹性研究

软木是从栓皮树上采剥的树皮,是一种天然可再生的生物质材料。通过对软木的动态黏弹性进行研究,可以揭示许多关于软木材料结构和分子运动的相关信息。本试验主要运用动态力学分析技术研究了栓皮栎软木的动态黏弹性,并和国外栓皮槠软木进行了对比。结果表明:在不同测试频率条件下,再生栓皮栎软木的储能模量(E~')均随温度升高而呈现降低趋势,损耗因子(tanδ)曲线主要出现了3个明显的损耗峰,对应的3个损耗过程分别由软木脂无定形区发生玻璃化转变、软木中有关成分发生熔融和吸着水的损失、纤维素和半纤维素发生热软化或降解所引起。再生栓皮栎软木分别沿轴向、径向和弦向进行拉伸测试时,E~'、损耗模量(E~″)和tanδ曲线的变化趋势基本一致,但在相同测试温度下,E~'和E~″在3个方向存在明显差异。在本试验条件下,栓皮栎和栓皮槠软木存在不同温度的损耗峰,主要表现为初生和再生栓皮栎软木的tanδ曲线分别在-10和-19℃出现一个损耗峰,而再生栓皮槠软木对应的损耗峰出现在14℃。     

蒸煮处理对栓皮栎软木主要物理特性的影响

研究了沸水不同蒸煮处理时间对秦巴山区初生和再生栓皮栎软木的微观结构、物理特性和表面色度学参数的影响。结果表明,沸水蒸煮可使栓皮栎软木细胞膨胀、细胞壁褶皱减少。在试验范围内,沸水蒸煮可使栓皮栎软木体积增大、密度降低,初生和再生软木体积膨胀率分别为15.4%17.1%和24.8%26.8%,密度变化比值均小于1。不同时间沸水蒸煮处理后,初生和再生软木的径向尺寸变化明显大于轴向和弦向。与未处理软木相比,沸水蒸煮可降低软木硬度和压缩回弹率,蒸煮处理1h后,初生和再生软木压力释放24h后的压缩回弹率分别为85.20%和84.23%,硬度变化比值分别为0.804和0.724。沸水蒸煮后软木表面明度降低,蒸煮前后的总体综合色差随着蒸煮时间的延长而增大。     

栓皮槠软木微观构造和化学成分的研究

以百林软木制品有限公司提供的阿尔及利亚栓皮槠(Quercus suber)软木及天然红酒塞为原料,对其细胞结构和化学成分进行研究,为红酒塞中的2, 4, 6-三氯苯甲醚(TCA)去除提供一定的指导作用。使用场发射扫描电镜观察软木的微观形态;分析栓皮槠软木的化学成分。结果表明:栓皮槠软木细胞是排列紧密的薄壁细胞,无细胞间隙。横切面和径切面成行排列,类似砖墙状;弦切面上呈现蜂窝状;软木细胞部分细胞壁上有明显褶皱,可能对TCA的去除有一定的影响。软木的各种化学成分含量为:灰分0.52%,抽提物总量13.28%,木栓脂43.41%,酸不溶木质素22.98%,纤维素3.40%,半纤维素16.41%。     

针叶树原生质体培养的现状

植物细胞由细胞壁所包被,细胞壁主要是由纤维素、半纤维素和果胶质等成分构成。细胞壁的实际构成成分取决物种及其发育环境。细胞壁具有一定的硬度和膨压,因而它的作用是保持细胞结构。没有细胞壁而只有质膜包被的细胞称为原生质体。在植物育种     

普通油茶炭疽病菌体内外产生的果胶酶

<正> 普通油茶炭疽病的发病是从炭疽菌(Colletotrichum camelliae Massee)穿透寄主细胞壁开始的。病原菌穿透寄主细胞壁的能力除穿透钉的机械性渗透压力之外,还包括细胞壁成分的酶降解活动。病原菌侵入后在寄主组织中扩展,主要也是由于它所分泌的酶系统侵解寄主的细胞壁。因此,炭疽病菌产生多糖降解酶的能力,可能是具有致病能力的一个重要的特征。植物细胞壁的降解需要有能分解纤维素、半纤维素、果胶质和蛋白质的酶系统,其中只有果胶酶由于它在整个降解细胞壁过程中的有效性和它在病程中致死寄主细胞的效能,这类     

软木细胞壁化学组分及软木材料应用探析

对栓皮栎与栓皮槠两树种的软木细胞结构、主要化学组分进行综述,并介绍了软木材料的主要应用形式,以期为进一步的软木理论研究及应用开发提供参考。     

软木的热解特性和热动力学研究

软木是一种天然多孔性绿色材料,具有吸音减震、隔热保温、滞火阻燃、耐酸碱、不易老化、富有弹性、无毒无味等一系列优良特性。由于它所独具的各种特性,特别是软木的热学性能,使其在工业生产与人民日常生活中都有广泛的应用。本文通过热重分析仪来研究软木的热学性能,在实验温度从303~873K的范围内,对产自湖北和云南的2种软木的热解过程进行了分析。结果表明:软木热解过程分为4个阶段,热解过程与化学成分的热解过程相一致,513~693 K是试样热解的主要阶段。根据热分解速率方程,获得了软木的动力学参数——频率因子A和活化能E,最后得到软木的热解动力学方程。     

新型软木橡胶地板投放市场

西安林化厂开发出新型软木橡胶地板新产品,日前已小批量投放市场。倍受用户青睐。软木橡胶地板是以优质天然软木(栓皮)为主要原料,以无污染型橡胶做胶合剂制成的新型高级弹性地板贴面砖,产品主要性能指标达到了国际标准 ISO3813,填补了国内空白。由于软木具有奇特的多孔薄壁细胞结构,产品具有优异的防滑性能和吸音、隔振效果,     

国内外软木研发进展与我国对策

软木是以栓皮栎的栓皮为原料,具有弹性、保温隔热、防滑耐磨、消音减震、安全无毒等特性的一种可再生绿色材料,产品广泛用于国计民生等重要行业和领域。文中介绍了世界软木资源分布情况、软木用途和产业趋势,综述了国内外软木细胞结构、化学成分、工艺与产品研发等概况,在比较欧美各国与我国软木产品标准制定/修订现状的基础上,概述了我国对现行软木纸标准LY/T 1320-2010和软木纸试验方法LY/T 1321-2013的修订研究过程。提出了加强我国软木研发的建议,即紧跟软木脂研究国际前沿,加大软木脂基础与应用技术研究;加强软木行业标准建设,实现软木产品标准国际化、单项化、功能化;加强软木产品开发利用以及软木资源的培育以提升我国软木产品竞争力,促进我国软木行业健康快速高效发展。     

栓皮栎软木的微观构造

栓皮栎(Quercus-variabilis)或栓皮槠(Q.suber)树皮部分的木栓层通常称为"软木",英文为cork或者phellogen,与通常所说的针叶材软木(softwood)不同.软木独特的细胞构造及其化学成分使其具有质轻、弹性好、隔热、隔音、隔水、防潮、阻燃、柔软、耐磨等优良特性,素有"软黄金"之称(郑志峰,2005).     

The thermochemical degradation of cork

Summary The thermochemical degradation of cork from Quercus suber L. was studied in the temperature range 150°C–450°C in relation to mass loss, chemical composition and the influence on the cellular structure. The degradation of cork is strongly dependent on temperature and mass losses become significant at 200°C (15% of initial dry weight) and increase rapidly for higher temperatures (27% at 250 °C, 49% at 300 °C, 62% at 350 °C) until ashing at 450 °C. The polysaccharides are the most heat sensitive components: at 200 °C, hemicelluloses disappear and cellulose is degraded to a considerable extent. Suberin is more resistant and degradation starts at approx. 250 °C; 300 °C-treated samples only contain 7% suberin.The cellular structure of cork is also significantly influenced by temperature. Upon heating, cells expand and the cell walls stretch, attaining at 250 °C a maximum cell volume increase corresponding to a factor of approximately 2. Above 300 °C, the structure of cell walls is considerably changed and show profound physical damage; in the later stages of pyrolysis, a cellular structure is no longer observed.We are grateful to Mrs. Joaquina Ferreira for her help with the chemical analysis. The research was financially supported by the Junta Nacional de Investigação Científica e Tecnológica (JNICT) and by the Instituto de Ciência e Tecnologia dos Materiais (ICTM)     

Cellular structure and chemical composition of cork from the Chinese cork oak (Quercus variabilis)

Quercus variabilis Blume, the Chinese cork oak, is an oak species with a thick cork outer bark. The cork is exploited at a limited scale in China and considered of lower quality than the commercial cork from Quercus suber. We studied an industrial cork granulate feedstock of Q. variabilis in relation to cellular structure and chemical composition and compared it to Q. suber cork under a material’s perspective. The cork of Q.variabilis has 1.1 % ash, 9.6 % extractives, 34.8 % suberin and 19.1 % lignin. The monosaccharide composition with shows a predominance of hemicelluloses: glucose 42.8 % of total neutral sugars, xylose 27.5 %, arabinose 15.4 %, galactose 9.0 %, mannose 4.0 %, rhamnose 1.2 %. The FT-IR spectrum shows the indicative peaks of suberin. The composition is overall similar to that of Q. suber cork. Q. variabilis cork has the typical cellular characteristics of bark cork tissues with a regular and radially aligned structure of cells without intercellular voids. Solid volume fraction was estimated at approximately 16 %. Compared with Q. suber, the Q. variabilis cork cells are smaller, the cell wall undulation and the overall row alignment less homogeneous, the cell surface is irregular and the solid volume proportion higher. The characteristics of Q. variabilis cork support its use as a cellular material for sealing, insulation and energy absorption, but the overall quality is lower than that of Q. suber cork. The negative impact of the higher density and structural lower uniformity at tissue and cell level should be evaluated for processing and product performance.     

Variability of the compression properties of cork

The variability of the compression properties of cork was determined after field sampling covering the main production area in Portugal (10 sites) with samples taken from 20 trees per site at the time of cork stripping. In all cases, cork showed compressive stress–strain curves typical for cellular materials, which are characterized by an approximately “elastic” region up to a 5 % strain, followed by a large plateau up to 70 % strain caused by progressive buckling of cell walls, and a steep stress increase for higher strains corresponding to cell collapse. The radial direction of compression offered higher strength. The Young’s moduli averaged 10.4 and 9.2 MPa for radial and non-radial directions, respectively, spreading from 3.5 to 22.5 MPa for the non-radial and 4.2 to 21.5 MPa for the radial directions. The geographical location of cork production was the major factor of variability. Density, annual growth ring width and chemical composition influenced compression. Cork samples with higher density showed overall larger resistance to compression. The energy absorbed per unit volume to achieve the maximal deformation with full densification of cork is higher when the average annual ring width is smaller. Cork samples with relatively higher suberin content required less stress for deformation. The results encompass the natural variability of cork and are the most extensive to characterize cork. They allow a better insight into the differences that may explain the variation in cork properties and strengthen its use either in the known applications, i.e. as a sealant, or in novel applications.     

Effects of water vapour heating on structure and properties of cork

Summary The effects of heating cork in water vapour at 100°C and 300°C are studied and compared with those produced by heating in air at the same temperatures. Dimensional and mass changes were measured and radial compression curves were obtained following various treatments. The 300°C treatments originate a straightening of the originally corrugated cell walls, while the cell wall material undergoes thermal degradation. Larger swellings and larger mass changes are observed in the treatments in water vapour as compared to those in air. The 100°C treatments do not induce degradation and produce reversible changes in technological properties which are simply due to differences in the water content.     

A chemical and ultrastructural study of the Bamboo species Phyllostachys makinoi Hay

Summary A culm sample of Phyllostachys makinoi was investigated by analysis of its chemical composition, and by electron microscopic observations of the cell wall structure before and after extraction and degradation procedures. Quantitative determination of the components resulted in 2.6% extractives, 25.5% lignin, 45.3% alpha-cellulose, and 24.3% polyoses. The main polyose is an arabinoxylan with a Xyl: Ara ratio of about 17:1. The electron micrographs show a lamellar deposition of lignin and polyoses within the secondary walls. Lignin is obviously soluble by parts in alkaline as well as in acidic reagents. Sodium hydroxide solution removes cell wall substance mainly from the secondary walls, whereas trifluoroacetic acid removes substance from compound middle lamellae.     

Growth stresses and strains in cork

Summary A detailed study of the growth stresses and strains in the cork shell of the cork-oak was undertaken based on experimentally determined constitutive relations for cork in tension and compression. The stresses depend on the thicknesses of the cork shell and of the back layer around the cork shell, on the radius of the trunk and on its increase due to growth. The circumferential stresses in the cork shell and back layer are tensile and increase with increasing distance to the tree axis. The radial stresses are compressive and decrease with increasing distance to the tree axis. The strains due to growth are not recovered when the cork boards are removed, unless the boards are heated, for example, by immersion in boiling water. Other consequences of the growth stresses are analysed, such as the occurrence of corrugations in the lateral cell walls of cork, the variation of width of the successive growth rings and the occurrence of cracks in the back layer and outer cork layers.