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51.
52.
麦草碱木素是我国造纸工业重要的剩余物,但是麦草碱木素的结构决定了其反应活性较低,从而使其应用受到较大的限制。笔者根据麦草碱木素的特点分别对比超声破碎仪不同的超声条件(时间:10、20、30、40min;振幅:60、80、100)和不同的溶液质量比(100:0,60:1,20:1)对麦草碱木素的活化效果,并探索用活化后的木素代替部分苯酚(10%、20%、30%、40%)制备酚醛树脂胶黏剂的可行性。研究结果表明:超声波作用可显著提高酚羟基的含量。超声波作用时间在20min、振幅80、溶液质量比20:1时效果相对较好。经过超声波活化的木素按20%的量替代苯酚制备LPF,压制的胶合板的胶合强度都达到国家Ⅰ类胶合板的要求,并能与未改性的酚醛树脂(PF)胶黏剂相媲美。 相似文献
53.
Pine wilt disease (PWD), recently introduced into Europe, is caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus and is a devastating illness that affects mainly pine trees. It is known that the PWN is capable of infecting other conifers; however, there is currently no information on which other plant species may be susceptible to PWD. In this study, the potential susceptibility of two common species of European forests, Picea abies and Cupressus lusitanica, to PWN was assessed through the monitoring of visual external symptoms, dimension and localization of the nematode population in stems, quantification of total chlorophyll, total soluble phenolics and lignin, at 7, 14, 21 and 28 days after inoculation. The degree of susceptibility was established through the comparison of symptoms with Pinus pinaster, a well‐known PWN host. Furthermore, the stem ultrastructure of P. abies, C. lusitanica and Pn. pinaster was analysed by scanning electron microscopy. The results suggest that P. abies and C. lusitanica are resistant to PWN, and that lignin biosynthesis in these species is affected at an early stage of the infestation. Nevertheless, P. abies seems to be a compatible host that could act as a repository for PWN. 相似文献
54.
XU Jinmei ZHAO Rongjun FEI Benhua Research Institute of Wood Industry Chinese Academy of Forestry Beijing P.R.China 《中国林业科技(英文版)》2007,6(3):45-50
The objective of this study is to determine the properties of G. amplexifolia. In this paper; the chemical composition, including holocellulose, acid-insoluble lignin, 1% NaOH solubility, benzene-ethanol extractives and ash content, was considered for the variability with respect to positions along bamboo culm height (bottom, middle and top), parts along radial direction (inner part and outer part)and ages (1-year and 2- year). The test results were also compared to those of moso that is commonly planted and used in China. This study indicated that both the holocellulosecontent and the lignin content in inner part were lower than ; in outer part, but for extractives and ash content, the reverse was true. Bamboo age also had effect on chemical composition; both the holocellulose content and the ash content in the culm of 1- year were higher than those of 2-year; while the lignin content and the extractive content m the culm of 1- year were higher than those of 2-year. High holocellulose content, low lignin contentand extractive content were advantages of G. amplexifolia. 相似文献
55.
To elucidate the formation mechanism of acidsoluble lignin (ASL) formed in the Klason lignin determination, beech wood meals were treated with sulfuric acid (SA) under various conditions, and the ASL solution was extracted with CHC13. The results indicated the following: (1) wood components yielding ASL are dissolved in 72% SA during the initial stage; (2) the quantity of ASL is highest during the initial stage, then decreases with prolonged time of 72% SA treatment and finally reaches a constant value; (3) soluble lignin prepared by 72% SA treatment and subsequent standing in 3% SA again yield insoluble Klason lignin and ASL after boiling in 3% SA; and (4) about half the amount of ASL is dissolved in CHC13. The foregoing suggest that wood components yielding ASL are dissolved in 72% SA at the beginning and finally change to ASL after being subjected to depolymerization, hydrolysis, and other reactions. ASL may thus be composed of low-molecular-weight degradation products and hydrophilic derivatives of lignin. 相似文献
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57.
研究了影响木质素与低密度聚乙烯(LDPE)共混物在转矩流变仪中的共混最大扭矩、平衡扭矩以及达到平衡扭矩时间的各个因素。结果表明,木质素、淀粉降解母料、增塑剂、温度对扭矩有明显影响;在LDPE为100份时,木质素55份,淀粉母料25份,增塑剂占木质素7.5%,增容剂10.5份,温度为180℃,共混物塑化性能最优。 相似文献
58.
木质素电氧化的影响因素研究 总被引:3,自引:0,他引:3
木质素是天然高分子聚合物,具有一定的化学反应惰性。本文率先研究草类木质素在膜助电解时的电化学氧化作用。其结果表明:膜助电解对黑液中的有机物具有一定的氧化作用,能使木质素中的芳环被氧化而打开;同时木质素的氧化作用与施加的电压、阳极的电极材料等因素有关。通过对木质素氧化产物结构的进一步研究,可为木质素的电化学改性提供了新的方法。 相似文献
59.
3种白腐菌木质素降解酶的比较 总被引:1,自引:0,他引:1
对3种白腐菌——黄孢原毛平革菌、变色栓菌和木质层孔菌在恒温振荡培养条件下产漆酶、锰过氧化物酶的情况进行比较研究,同时还对此3种菌在培养过程中还原糖的变化作了研究.结果表明:3种白腐菌中变色栓菌产漆酶相对最高,其漆酶酶活最高达到136.5 U/L,产酶最高时间为第8天;而木质层孔菌产锰过氧化物酶相对最高,其最高酶活达到880.2 U/L,产酶最高时间为第8天;同时在培养过程中还原糖含量随培养时间的延长而逐渐降低. 相似文献
60.
The content of the glyceraldehyde-2-aryl ether-type structure in water-soluble lignin–carbohydrate complex (LCC) fractions, which were obtained from Japanese cedar and birch residual wood meal after milled wood lignin isolation, was determined by ozonation. Quite high amounts of the glyceraldehyde-2-aryl ether-type structure were found in water-soluble LCC fractions of both species; about 3–5 times higher than those of other fractions. This result, as well as the high content of the β-1 structure in these fractions shown in our previous reports, suggest that lignin in these fractions has the characteristics of endwise-type lignin, because the glyceraldehyde-2-aryl ether-type structure and β-1 structure are typical characteristics of this type of lignin fraction. These results are in good agreement with the generally accepted hypothesis that the glyceraldehyde-2-aryl ether-type structure and β-1 structure are generated at the same time by a radical coupling reaction. The results also indicated that these two structures are present in close proximity in the lignin. 相似文献