Ground kenaf core as a filtration aid

The objective of this study was to examine the filtration characteristics of ground kenaf core, a waste material generated during the production of kenaf bast fibers for paper. The constant-pressure precoat filtration characteristics of ground kenaf core were compared to commercial diatomaceous earth (DE). Three challenge solutions were studied: a yeast solution, a bacterial solution, and a standard silica-particle solution. The kenaf and DE both satisfactorily permitted removal of all silica particles from solution without noticable flux degradation over the course of the filtration. The kenaf and DE also removed yeast particles. In this case, the flux loss with time was lower with the DE precoated filter than in the kenaf precoated filter. The DE precoat excluded less than 10% of the bacterial particles from solution, whereas the kenaf removed about 40% of these small particles.     

黄红麻脱胶工艺初探

本文对黄红麻纤维的化学脱胶工艺作了初步的探索，实验结果表明，脱胶后的黄红麻纤维性能有了较大的改善，为精细化黄红麻产品提供了基础。     

Weibull distribution analysis of the tensile strength of the kenaf bast fiber

This paper presents the influence of the gage length on the kenaf fiber Young’s modulus and the tensile strength characterization. Four different gage lengths of 10 mm, 15 mm, 20 mm and 25.4 mm are selected in this study and the tensile testing is performed at a quasi-static loading rate of 1 mm/min. The cross-sectional area of the fiber after failure is considered for the stress calculations. Weibull probability distribution is used to characterize the tensile strength of the kenaf fiber. The Weibull parameters are obtained for the two parameter, three parameter and Weibull of Weibull models and the average tensile strength of the fibers are evaluated. The predicted average tensile strength from all the three approaches are in good agreement with the experimental results for the obtained parameters.     

Relationship between chemical composition,crystallinity, orientation and tensile strength of kenaf fiber

The physical properties of natural growth fibers such as chemical composition content and fiber diameter are highly affected by environmental issues such as environmental changes and fiber extraction methods. These irregularities of the natural fibers seriously affect its utilization in composite as reinforcements. In this study, taking into account the importance of the fiber tensile strength, the correlation degrees between the kenaf fiber tensile strength and the fiber chemical composition, crystallinity, orientation degree were analyzed by the grey relational analysis method. Both the kenaf single fiber and fiber bundle were used as XRD and tensile strength test sample. The chemical composition content and the FTIR were carried out to obtain a correct result of the chemical composition content. It found that for the different XRD and tensile strength test samples, the single fiber showed lower crystallinity, higher orientation degree and tensile strength compared with the fiber bundle. The cellulose content and the orientation degree got the higher correlation degree with single fiber tensile strength, which was 0.674 and 0.640. The highest factor associated with the fiber bundle tensile strength was the orientation degree, the correlation degree was 0.747. The hemicellulose content and the crystallinity also got high correlation degree with the fiber bundle strength, which was 0.687 and 0.640.     

Thermal Characterization of Alkali Treated Kenaf Fibers and Kenaf-Epoxy Composites

Chemical treatment of natural fibers is a well-defined means of mechanical property improvement in natural fiberreinforced composites. An understanding of mechanical and thermal properties in these media is essential for evaluating heat transfer, thermal degradation, and overall performance of these composites over their product lifetime. However, very little information is available illustrating the effect of such treatment on the thermal properties of kenaf composites. Also, no study to date has reported the thermal conductivity of individual kenaf fibers. This study reports the effects of fiber treatment (in 6 % NaOH) on thermal transport in unidirectionally oriented kenaf-epoxy composites and individual kenaf fibers. The effective thermal conductivities and thermal diffusivities of chemically treated fiber composites show a general increase over untreated fiber composites (0.210 to 0.232 W/m/K at 28 °C, 0.206 to 0.234 W/m/K at 200 °C). This improvement may be attributed to improved interfacial contact between the fibers and epoxy matrix shown in microstructural images after chemical treatment. The thermal conductivity of individual fibers was evaluated at room temperature using two techniques. Results from both techniques showed slight increases after chemical treatment (0.58±0.53 to 1.0±0.13 W/m/K and 1.2±0.54 to 1.6±0.28 W/m/K) but lacked statistical significance. Any improvement in surface crystallinity after chemical treatment does not appear to affect overall fiber thermal conductivity. A better understanding of thermal transport in kenaf fibers and composites enables better estimation of the performance of these composites in different applications. Moreover, the thermal conductivities of individual fibers are useful in understanding the fiber’s contribution to conduction in different fiber reinforcement configurations.     

Study on kenaf flame retarded by halogen-free flame retardant/HIPS composites

In order to improve the thermostability and fire resistance of kenaf, kenaf was treated with halogen-free flame retardant triethyl phosphate (TEP) adopting dipping principle. Adding flame retardant kenaf (fbk) to high impact polystyrene (HIPS) resin, fbk/HIPS composites were prepared by extrusion molding and injection molding. The differences of untreated kenaf and treated kenaf on structure, thermal behavior, combustion, mechanical properties of HIPS were contrasted and analyzed. The results showed that kenaf treated with TEP had superior thermal stability at high temperature and produced significantly reinforcing effect on HIPS resin.     

黄麻和红麻纤维磨木木质素的红外光谱特征

从黄麻和红麻纤维中分离出磨木木质素,利用红外光谱分析了两种麻纤维磨木木质素的特征峰及归属,得知磨木木质素中有复杂的官能团,含有羟基、羰基、甲基等基团,木质素结构中含有相当数量的紫丁香基单元。根据黄麻和红麻纤维磨木木质素的红外光谱吸收峰强度,推断其结构属于阔叶木类木质素化学结构GS型木质素。     

Sound absorption and viscoelastic property of acoustical automotive nonwovens and their plasma treatment

Sound absorption property, viscoelastic property and the effect of plasma treatment of four automotive nonwoven fabrics on these properties are discussed in this research paper. Needle-punched fabrics used for vehicle headliner include 2 polyester fabrics made of hollow polyester fibers or solid polyester fibers, and 2 polypropylene-composite cellulose fabrics made of jute fibers or kenaf fibers, manufactured with the same web structure of apparent fabric density and fabric thickness. Hollow polyester fiber fabric has the highest sound absorption and the highest loss factor, the second highest is jute fiber fabric. The viscoelastic property is found to be related to the sound absorption property of fabric. The plasma treatment on nonwoven fabrics changes their sound absorption and viscoelastic property as well as their fabric weight and pore size. Hollow polyester fabric shows the increased sound absorption and viscoelastic property after the treatment with the increased pore sizes, while regular polyester fabric displays insignificant changes. The cellulose fabrics are more affected by plasma treatment compared to the polyester fabrics in terms of fabric weight loss and pore size, and jute fabric is more affected than kenaf fabric due to fiber weakness. The jute fabric demonstrates the decreased sound absorption and viscoelastic property, while kenaf fabric shows the increased sound absorption with the unchanged viscoelastic property after the treatment.     

Development of polyurethane based conducting nanocomposite fibers via twin screw extrusion

In the present study, conducting nanofillers are incorporated in thermoplastic polyurethane (TPU) to produce nanocomposite fibers through melt compounding route using micro twin screw extruder attached to a fiber drawing device. Nanocomposite fibers using bulk graphite, nanographite and carbon nanofiber were produced using varying amounts of these nanofillers. Metal coated nanographite, new hybrid nanoparticle produced in house, were also used to impart conductivity to the TPU fiber. The process parameters such as processing temperature, mixing time and rpm of the screw have been optimized considering minimum change in TPU bulk properties. It has been found that the nanofillers can be melt mixed safely up to 4 min with the TPU at 180 °C and 100 screw rpm. These mixing conditions give reasonable amount of dispersion. The studies on such fibers in differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA) reveals that the metal coated nanographite particles make the nanocomposite fibers more thermally stable. Both the D. C. conductivity and A. C. impedance of the nanocomposite fibers have reduced significantly even at very low loading of nanofillers, although the conductivity of the produced fibers are in antistatic range (D.C. conductivity ～10^?4 S/m).     

Improving the use of kenaf for kraft pulping by using mixtures of bast and core fibers

Kenaf (Hibiscus cannabinus L.) is a herbaceous annual plant amenable to use as a papermaking raw material. Kraft and soda pulping of kenaf have so far been done exclusively on the bark fraction (about 34–38% of the stem) or whole stem of the plant. Using kenaf bark exploits the higher quality of its bast fibers but reduces the typically high crop yields of this plant. In any case, core kraft pulp has acceptable properties some of which (e.g. tensile index, burst index) can even surpass those of bark pulp. Pulp made from both fractions has been found to exhibit better bonding properties than bark pulp. However, too high a proportion of core fibers can result in difficult drainage, a low tear strength or poor air permeability. These problems restrict the proportion of core that can be mixed with bast fibers, hinders separation of the two fractions and raises operational costs.The primary purpose of this study was to examine the influence of the core–bark ratio on the properties of mixed kenaf pulp. We used unrefined core pulp and refined bark pulp. Based on the results for kraft sacks, obtaining kenaf paper from both fractions has some advantages. Because Gurley air porosity changed dramatically with the proportion of core pulp used, it was used to determine the maximum amount of core fibers to be added to bast fibers. A proportion of up to 34% was found to have no adverse effect on air permeability. Such a proportion allowed paper strength to be preserved with an acceptable tear index (19.8 mN m²/g) and excellent tensile index (72 N m/g). Also, energy consumption was reduced if only the bark fraction was refined. The proposed strategy thus provides increased fiber yields of kenaf per hectare per year and valorizes the core fraction.     

Frost kill and kenaf fiber quality

Kenaf (Hibiscus cannabinus) grown in northern Mississippi and elsewhere often is injured by early frost and killed before harvest. Frost kill often is associated with fungal growth or rot, so its effect on fiber quality is a major concern. Fiber processing also affects the quality and chemical composition of fibers. Therefore, this study was aimed at determining the effects of frost kill on processing, fiber quality and chemical composition of kenaf fibers. Frost-damaged kenaf with fungal growth was decorticated by hand and divided into six sections (26.88 cm/each) from the base to tip of the stem and then retted chemically or bacterially in the laboratory. Fiber characteristics were compared between the two processes and the six locations on the plant. Ash, cellulose, hemicellulose, and lignin contents of the resultant fibers were measured. Bacterially retted (BR) fibers were stronger (11.8 g/tex) than the chemically retted fibers (CR), 7.5 g/tex, at all locations. The BR fibers from decorticated green ribbons were stronger than those from frost-killed ribbons. However, no significant differences occurred between the CR fibers from decorticated and frost-killed ribbons. Residual gum content was higher for the BR fibers (23.3%) than for the CR fibers (8.1%). The stretch properties were not affected significantly by the frost kill or fungus. The base of the stem had the weakest fibers in both processes, which may have been due to greater fungal disease. The CR process extracted more fiber than the BR process, with a consistent higher yield of clean fibers. In the BR process, the fiber extracted was higher at the tip than at the base of the stem. This may have been related to the presence of fungus, which inhibits the BR process. Analysis of chemical composition of the processed fibers indicated that CR is efficient in reducing hemicellulose and lignin contents. These results indicate that frost kill may not be the appropriate method for harvesting kenaf for quality fibers. However, fibers extracted by chemical retting were unaffected by the presence of fungus as a result of frost kill.     

The effects and roles of PVP on the phase composition, morphology and magnetic properties of cobalt ferrite nanoparticles prepared by thermal treatment method

Cobalt ferrite nanocrystals were prepared from an aqueous solution containing metal nitrates and various of concentrations of poly(vinyl pyrrolidone), followed by calcinations temperature. X-ray diffraction (XRD) analysis was performed to determine the degree of crystallinity of the ferrite nanoparticles. By transmission electron microscopy (TEM), the morphology and average particle size of the cobalt ferrite nanoparticles were evaluated which had good agreement with XRD results. Fourier transform infrared spectroscopy (FT-IR) suggested the presence of metal oxide bands in all samples as well as the effective elimination of organic constituents after calcinations. Vibrating sample magnetometer (VSM), was utilized to evaluate the magnetic properties of the cobalt ferrite nanoparticles.     

Pulp and paper from kenaf bast fibers

Samples of kenaf (Hibiscus cannabinus) grown in Malaysia were examined to determine the kraft pulp and papermaking properties of their bast (or bark) fibers. Using kraft pulping process showed that bast fibers were relatively easy to cook resulting good pulp yields in the range of 45–51%. The bast pulp produced sheets with great density, tear index and dry zero-span breaking length. Kenaf bast fiber is considered promising for production of high-grade printing, writing and specialty papers.     

红麻种质资源耐旱性的初步鉴定研究

为鉴定和筛选红麻耐旱种质资源,本研究选用10份红麻野生种和41份红麻栽培品种为材料,51个红麻种质资源进行盆栽和干旱胁迫试验鉴定,根据干旱后叶子的萎蔫程度进行鉴定、比较,获得了51个红麻种质资源的耐旱性评价。已鉴定和筛选出的7个耐旱性较强和8个耐旱性较弱的红麻种质材料,结果对红麻种质资源的评价和进行红麻耐旱性的分子基础研究有一定指导意义。     

Water absorption characteristics of kenaf core to use as animal bedding material

Kenaf is grown these days as a minor fibre crop in some Asian countries, but also in the US and recently in Southern European countries such as Italy. The yield of extracted bast fibres is below 1/3 of that of the kenaf stem weight. In the US and Europe a profitable outlet for the remaining woody core is important for economical production of the crop. The use of kenaf core as animal bedding material is considered here as potential market outlet. An important aspect for this application is the moisture absorption capacity of the material. This paper describes evaluation of the water absorption capacity of different kenaf core fractions in comparison with other commercial animal bedding materials like straw and wood shavings. The water absorption of kenaf core particles is shown to be in the range of the other tested materials and especially the soft pith material showed very high absorbency.     

改良CTAB法用于提取红麻成熟叶片高质量DNA的研究

红麻处于光合高峰期的成熟叶片中的次生物质含量很高,给DNA的提取造成很大的困难.CTAB法能有效去除多糖杂质,但普通CTAB法用于红麻的DNA提取效果很不理想,为使CTAB法能更好地用于红麻的DNA提取,我们对此方法进行了改进,通过前处理除去大部分的杂质,减小了后续操作的难度.为了验证前处理是否会损失DNA,研究了液氮研磨对材料细胞的破碎程度问题,还讨论了DNA提取中的其它一些相关问题.     

改良CTAB法用于提取红麻成熟叶片高质量DNA的研究

红麻处于光合高峰期的成熟叶片中的次生物质含量很高,给DNA的提取造成很大的困难。CTAB法能有效去除多糖杂质,但普通CTAB法用于红麻的DNA提取效果很不理想,为使CTAB法能更好地用于红麻的DNA提取,我们对此方法进行了改进,通过前处理除去大部分的杂质,减小了后续操作的难度。为了验证前处理是否会损失DNA,研究了液氮研磨对材料细胞的破碎程度问题,还讨论了DNA提取中的其它一些相关问题。     

Multiple buds are an alternative target to genetic manipulation of kenaf (Hibiscus cannabinus L.)

Kenaf (Hibiscus cannabinus L.) is an annual fiber crop cultivated as an important source of cellulose and lignin. In the recent years, fibers have increased their economic importance as organic component in bio-composite materials. However, industry requires rheological improvements of these fibers. Genetic manipulation has been considered a feasible approach for fiber improvement; however, kenaf is considered a crop species difficult to manipulate. Here we propose meristematic cells from mature embryos as target for genetic modification driven by Agrobacterium tumefaciens. In vitro meristems proliferation and multiple shoots regeneration were evaluated by sowing kenaf mature seeds on medium containing three different concentration of thidiazuron, a substituted urea compound. The highest number of regenerated shoots was obtained from mature seeds germinated in presence of 10 μM thidiazuron after 14 days of culture. Interactions between two A. tumefaciens strains and two kenaf varieties were assessed. Transgene stable integration and its inheritance in T₁ generation were also verified, demonstrating that kenaf meristematic cells are an useful target for genetic manipulation by agroinfection.     

Water soluble carboxymethylcellulose fibers derived from alkalization-etherification of viscose fibers

Carboxymethylcellulose (CMC) fibers have been successfully prepared from viscose fibers through the process of alkalization-etherification. Parameters including reaction temperature, mass ratio of NaOH to the viscose fibers, and mass ratio of the viscose fibers to ethanol are studied. The degree of substitution (DS) and the inherent viscosity of the CMC fibers are determined. The CMC fibers are characterized by using Fourier transform infrared spectroscopy (FT-IR), ¹H-nuclear magnetic resonance spectroscopy (¹H-NMR), scanning electron microscopy (SEM), and the X-ray diffraction (XRD). The analysis demonstrates that under the experimental conditions where the reaction temperature is 40 °C, mass ratio of NaOH to the viscose fibers is 2.0, and mass ratio of the viscose fibers to ethanol is 1:15, the obtained CMC fibers possess an appropriate DS, better water-solubility, and lower degree of etching, thus they can be used as absorbable hemostatic fibers.     

红麻种质资源遗传变异和亲缘关系的RAPD分析

用随机扩增多态DNA（RAPD）方法对红麻种质资源的遗传变异和亲缘关系进行分析。6个引物对14份日本使用的红麻品种扩增出总共30条RAPD多态性条带。根据RAPD图谱模式可将红麻品种区分开来，区分范围从6份（用OPA－20引物扩增）到12份（用OPA－11引物扩增）的品种。用这30条多态性条带构建出的聚类分析树状图，将这14份红麻品种聚成源于印度、中国、越南的三大类。在随后进行的用四个引物对19份从美国引入的红麻种质资源的RAPD分析中，获得以35条多态性条带为基础的RAPD图谱并构建了树状图。结果认为这19份材料的大部分源于EI Salvador种系。起源相近或亲本来源相同的红麻品种资源随着时间、环境和人为等因素的影响农艺性状不断变异，但在DNA分子水平上的变异相对较小。根据红麻的农艺性状等很难判定品种的来源，而RAPD方法可区分鉴定品种以及明确品种资源间的亲缘关系。