Natural fibers for many and varied industrial uses are a current area of intense interest. Production of these fibers, furthermore, can add to farmer incomes and promote agricultural sustainability. Flax (Linum usitatissimum L.), which has been used for thousands of years, is unparalleled in supplying natural fibers for industrial applications as diverse as textiles and paper, providing high value linseed and fiber from a single plant, and maintaining sustainable agriculture in temperate and subtropical climates for summer or winter production, respectively. As a value-added replacement for glass fiber from a renewable resource, flax fiber is recyclable, biodegradable, and sustainable for the economy, ecology, and society. To the point, Daintier Chrysler reported that natural fibers for automotive components required 83% less energy and were 40% less expensive than glass fiber components. A better understanding of the fiber characteristics that influence composite performance could lead to the development of additives, coatings, binders, or sizing suitable for natural fiber and a variety of polymeric matrices. Stems of flax require retting to separate fiber from nonfiber components and rigorous mechanical cleaning to obtain industrial-grade fibers. Considerable work has been undertaken to improve the retting process using specific cell-free enzymes, especially pectinases, to control and tailor properties for industrial applications. Fiber processing and use in composites are affected by variables such as length, uniformity, strength, toughness, fineness, surface constituents, surface characteristics, and contaminants. One of the main concerns for the composite and other industries in incorporating natural fibers, such as flax, into production parts is the fiber variability resulting from crop diversity, retting quality, and different processing techniques. Standardized methods to assess flax fiber properties, therefore, are needed to maintain quality from crop to crop and provide a means to grade fibers for processing efficiency and applications. Other parts of the plant stalk, notably the waste shive and dust, can potentially be utilized as coproducts to offset costs for producing the major products of fiber and seed.

近红外线反射法NIRR (near-infrared reflectance)适用于风干的未受损伤的亚麻原茎的测定,也是对Fried法测试亚麻沤制程度的进一步发展。报道了优先选用自2号至12号波长设定的性能统计,推荐7号、9号或12号的波长模式。波长的设定来自于1432-至2468-nm的光谱域。标定的试样来自于经不同时间段用酶剂或螯合剂溶液沤制过的亚麻原茎。试样的光谱特性均在不同的水合作用、原茎取向和光学角度下测定;而其标定模式对这些反应都不敏感。均方根误差由全部有效交叉(cross-validation)的RMSECV测定;它是受限定的,以便保证每个测试样品对其设定的标定值具有独立性。对12号波长模式来说,在对沤制不足到沤制过分的试样,经过4个可视效果水平(0到3)的扫描测试后所得出的平稳的曲线上,其预定及测定之间的相关系数R2是0.946,而RMSECV是±0.20。研究员发现:在一个单独窗的实验中,12号波长的NIRR法测试结果的误差比Fried法的要少一些,其重复的均方根误差是0.25。然而,即使是设定最小的波长,在经过酶剂沤制的亚麻原茎,对其沤制不足或沤制过分的程度,都能非常成功地进行分级。波长的设定是用一个新程序来确定的:首先,对全部可能用的光谱域的性能作试验,以定位重复显示的光谱窗,然后从每个窗上挑选出最佳波长的标定值。而这个程序也可以从复合的线性回归的波长模式中求得,它能可靠地形成具有相似量纲的、全光谱上的、局部的最小平方回归模式;此外,这个方法非常容易发现它有最相关的光谱误差。

Chapter 2 What Are Natural Fibres? Dr. Danny E. Akin PhD, Dr. Danny E. Akin PhD Athens, Georgia, USASearch for more papers by this authorDr. Michaela Eder, Dr. Michaela Eder post-doctoral fellow Department of Biomaterials, AustraliaSearch for more papers by this authorDr. Ingo Burgert, Dr. Ingo Burgert research group leader “Plant Biomechanics and Biomimetics”, GermanySearch for more papers by this authorProf. Dr.-Ing Jörg Müssig, Prof. Dr.-Ing Jörg Müssig Professor of Biological Materials Hochschule Bremen, GermanySearch for more papers by this authorMrs. Tanja Slootmaker, Mrs. Tanja Slootmaker Faserinstitut Bremen e.V. (FIBRE), Bremen, GermanySearch for more papers by this author Dr. Danny E. Akin PhD, Dr. Danny E. Akin PhD Athens, Georgia, USASearch for more papers by this authorDr. Michaela Eder, Dr. Michaela Eder post-doctoral fellow Department of Biomaterials, AustraliaSearch for more papers by this authorDr. Ingo Burgert, Dr. Ingo Burgert research group leader “Plant Biomechanics and Biomimetics”, GermanySearch for more papers by this authorProf. Dr.-Ing Jörg Müssig, Prof. Dr.-Ing Jörg Müssig Professor of Biological Materials Hochschule Bremen, GermanySearch for more papers by this authorMrs. Tanja Slootmaker, Mrs. Tanja Slootmaker Faserinstitut Bremen e.V. (FIBRE), Bremen, GermanySearch for more papers by this author Book Editor(s):Prof. Dr.-Ing Jürg Müssig, Prof. Dr.-Ing Jürg Müssig Professor of Biological Materials Hochschule Bremen, GermanySearch for more papers by this author First published: 09 April 2010 https://doi.org/10.1002/9780470660324.ch2Citations: 5 Series Editor(s): Christian V. Stevens, Christian V. Stevens Department of Organic Chemistry, Ghent University, BelgiumSearch for more papers by this author AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: Introduction Cellulose Hemicellulose Pectin Lignin and Aromatic Compounds Fats, Waxes and Lipids Ash Water-Soluble Material Conclusion Fibre Types and Anatomy Structure–Function (Property) Relationships of Plant Fibres Stress Generation in Wood Fibres Acknowledgement Natural Fibres Hairs and Threads Plant Fibres References Citing Literature Industrial Applications of Natural Fibres: Structure, Properties and Technical Applications RelatedInformation

近红外线-傅里叶转化换光谱-拉曼光谱微分显微术可以用作成像，并不断确定对亚麻（Linum usitatissimum L）原茎组织中化学成份分布的位置。大约80μm的亚麻原茎截面，冷冻后再逐渐缓暖，并在相对湿度85％的条件下养生均衡3h；然后，将试样置于具有金色反射镜的显微镜载玻片上，并盖上盖玻片上。对所选用的组织截面，每次成像摄影利用约为185mW的集焦激光，所使用的拉曼光谱漂移范围是在16cm^-1的3600—300cm^-1用256—512扫描，采用能控制显微镜自动运转的微机以收集50-150μm区域、垂直空间6-10μm步进式的图像立位，并将数码照相机拍摄的相片转化为可见的照片，每次成像数据的收集需要6-10h。化学视图是根据特定光谱区域内的面积积分而产生的。化学视图从组织细胞方式上，显示了亚麻化学成分中所有主要组成的位置。在CH脂肪质延伸区域的2850cm^-1上有一个削尖的凸肩，它说明在角质层／薄壁组织上，明显地有蜡质存在。围绕在1600cm^-1上的光带是由于芳族链延伸的振动形成的；证明在木芯组织上有木质素，以及在薄壁组织上有色素。围绕在1175—1050cm^-1上的光带，是由于COC重原子的混合式的振动形成的；它说明在纤维细胞中聚集了最大量的碳水化合物，以及在木芯组织中很明显地只有较少的碳水化合物。此外，围绕在870800，515-476以及400—360cm^-1上的光带，表明了在薄壁柔软组织中有果胶、其他非纤维素性的聚糖和纤维素的存在。

This chapter contains sections titled: Introduction Historical Perspective Factors Influencing Testing and Standards in Flax Fibres Current Status for Flax Standards Current ASTM Flax Fibre Standards Summary of Standards Future Standards References

Flax (Linum usitatissimum L.) fibers can be blended with other short staple fibers, such as cotton (Gossypium barbadense L. or Gossypium hirsutum L.), processed into a yarn, and then manufactured into a fabric. Enzyme-retting is a new, experimental method that decomposes the pectinaceous and matrix substances to separate cellulose fibers from shives using pectinase-rich enzymes and chelators. Spinning tests were used to determine how well fibers were assembled to form yarn and provided an indirect measurement of fiber properties. Miniature spinning allows expanded predictive strategies for ranking fiber production methods such as enzyme-retting and resultant yarns beyond traditional fiber testing.

Agricultural by-products represent a considerable quantity of harvested commodity crops. The use of by-products as precursors for the production of widely used adsorbents, such as activated carbons, may impart a value-added component of the overall biomass harvested. Our objective in this paper is to show that flax shive and cotton gin waste can serve as a precursor for activated carbon that can be used for adsorption of trichloroethylene (TCE) from both the liquid and gas phases. Testing was conducted on carbon activated with phosphoric acid or steam. The results show that activated carbon made from flax shive performed better than select commercial activated carbons, especially at higher TCE concentrations. The activation method employed had little effect on TCE adsorption in gas or vapor phase studies but liquid phase studies suggested that steam activation is slightly better than phosphoric acid activation. As expected, the capacity for the activated carbons depended on the fluid phase equilibrium concentration. At a fluid concentration of 2 mg of TCE/L of fluid, the capacity of the steam activated carbon made from flax shive was similar at 64 and 80 mg TCE/g of carbon for the vapor and liquid phases, respectively. Preliminary cost estimates suggest that the production costs of such carbons are $1.50 to $8.90 per kg, depending on activation method and precursor material; steam activation was significantly less expensive than phosphoric acid activation.

Flax fibers are often used in reinforced composites which have exhibited numerous advantages such as high mechanical properties, low density and biodegradablility. On the other hand, the hydrophilic nature of flax fiber is a major problem. In this study, we prepare the soybean oil based composites reinforced with protein coated and lipid acylated flax fibers and compare their water uptake properties. Results showed that water resistance properties of the composites are improved where treated flax fibers are used. The composite with lipid acylation of the flax fiber exhibited to enhance tensile strength and water resistance properties. Influences of fiber length, fiber loading and pressure on mechanical properties are also reported.

Flax (Linum usitatissimum L.) is an agricultural crop that is being considered as cost effective alternative to glass in composites. Flax is nature's composite with strong bast fibers held together in bundles and located in the outer regions of the plant stem between the outermost cuticle-epidermis layer and the innermost, woody tissues. Agricultural production of this crop is environmentally beneficial because it is produced through photosynthesis and considered a naturally renewable and sustainable material. Its use in bio-based composites could help lessen our dependence on fossil fuels today and into the future. Despite the longevity of flax in world markets, particular problems exist to provide flax fiber economically for markets in the US and North America. Barriers to such provisions include consistent, high-quality retting methods, efficient processing of whole steins into cottonized fibers, and development of standards to judge fiber quality. Processability of plant stalks into usable fiber requires retting which selectively removes pectinaceous and matrix substances thus separating cellulose fibers from non-fibrous substances and easing mechanical cleaning. Enzymes have been tested for efficiency of retting, and recommendations are in place for particular fiber properties. Before this work began, no processing facilities existed in North America for producing high value fibers. To facilitate research on bast fiber retting and subsequent processing, the Flax Fiber Pilot Plant (Flax-PP), was designed and modified after the 'Unified Line'; it is the only research facility of this type in the US and effectively processes and extracts bast fibers from plant stalks. A separate cottonizing unit has been installed to complete processing of fibers for various applications. Each processing step creates a fiber product and byproduct both with potential uses in composites. The development of standards through ASTM International is a continuing project. Currently, emphasis is on new equipment to quantify properties of particular usefulness such as cleanliness, fineness, and color. The Flax-PP becomes a valuable tool for improving fiber processing and quality, and thus integrates all activities for a flax fiber industry in North America.

Plant cell walls are limited in bioconversion by aromatic constituents. Chemical and structural characteristics of specific cell walls in a variety of plants have been investigated in conjunction with their biodegradability using microscopic methods. Histochemistry, ultraviolet absorption microspectrophotometry, and response of cell walls to microorganisms and specific enzymes identified significant aromatics contributing to recalcitrance. Monocotyledonous plants, such as grasses, and dicotyledonous ones, such as alfalfa, have lignin-type compounds within the secondary walls and middle lamella of cell walls. Cell walls that are heavily lignified as shown by positive staining reactions with acid phloroglucinol and UV absorption near 280 nm appear to be the most resistant, with examples of vascular tissues in both monocots and dicots. Grasses, however, and especially warm-season species, are rich in low molecular weight phenolic acids ester-linked to sugars within their cell walls, occurring in both lignified and non-lignified cell walls. In non-lignified tissues of grasses, phenolic acids prevent microbial degradation and appear to be a major barrier to biodegradation, particularly in warm-season grasses, such as corn, millet, and bermudagrass. Modifications in amounts, types, and linkages of cell wall aromatics, either in naturally occurring mutants or cultivars developed by plant breeding, have effectively improved the biodegradability of lignocellulose. Microbial delignification by cellulase-less white-rot fungi as well as pretreatment with commercial ferulic acid esterases improve biodegradation of lignocelluloses. Cellulosic bast fibers, such as those from flax stems, are mostly free of lignin and are degraded by cellulases without further pretreatment. Recovery of aromatics after pretreatment or other processing means could provide value-added compounds and improve the economics of bioconversion. (C) 2008 Society of Chemical Industry and John Wiley & Sons, Ltd

Grass lignocelluloses, such as those in corn and switchgrass, are a major resource in the emerging cellulose-to-ethanol strategy for biofuels. The potential bioconversion of carbohydrates in this potential resource, however, is limited by the associated aromatic constituents within the grass fiber. These aromatics include both lignins, which are phenylpropanoid units of various types, and low-molecular weight phenolic acids. Structural and chemical studies over the years have identified the location and limitation to fiber degradation imposed by a variety of these aromatic barriers. For example, coniferyl lignin appears to be the most effective limitation to biodegradation, existing in xylem cells of vascular tissues. On the other hand, cell walls with syringyl lignin, e.g., leaf sclerenchyma, are often less recalcitrant. Ferulic and p-coumaric acids that are esterified to hemicellulosic sugars constitute a major limitation to biodegradation in non-lignified cell walls in grass fibers, especially warm season species. Non-chemical methods to improve bioconversion of the lignocelluloses through modification of aromatics include: (1) use of lignin-degrading white rot fungi, (2) pretreatment with phenolic acid esterases, and (3) plant breeding to modify cell wall aromatics. In addition to increased availability of carbohydrates for fermentation, separation and collection of aromatics could provide value-added co-products to improve the economics of bioconversion.

The cuticle of flax stems contains lipids that provide a protective barrier to pathogens and control moisture loss. These lipids include wax esters and long chain fatty alcohols or policosanols. Cuticle fragments generated during several different fiber processing operations retain these lipid compounds that represent a potential co-product. Samples of flax shives (i.e., lignified core tissues), processing dust, and cuticular fractions recovered from enzyme retting waste water were extracted on a laboratory scale with hot ethanol to remove the lipid compounds. Ethanol extracts were analyzed by gas chromatography to determine the amount and type of lipids recovered. The results demonstrated that hot ethanol effectively extracted the lipid compounds from cuticle fragments in all these samples. When the extract was cooled, the longer chain wax esters (i.e., chain length of 44 carbon atoms or larger) precipitated and could be separated from the shorter chain lipid components (i.e., fatty alcohols and aldehydes less than 44 carbons). Similar results were obtained using absolute ethanol or 95% ethanol (aqueous). This technique provides a very economical method to recover lipid fractions as potential value-added co-product from flax processing waste.

The aims of this study were to understand the genotypic variability in cell-wall composition and cell-wall accessibility to enzymes in select switchgrass plants obtained from two different populations derived from a base population of octaploid cultivars. Population C+3 was developed by three breeding generations for high digestibility and population C−1 developed by one generation of breeding for low digestibility. Above-ground biomass from 12 selected genotypes, three each with high or low digestibility within each population, was analyzed for their cell-wall aromatics and polysaccharides. The ratio of p -coumaric acid/ferulic acid was greater ( P ≤ 0.05) for the high-lignin C−1 population over the low-lignin C+3 population, although the amounts of these two phenolics did not differ between populations. Combined values of guaiacyl + syringyl-lignin were consistently higher in genotypes from the C−1 population as compared to the genotypes from the C+3 population. Overall, p -coumaric acid was released by enzymes in greater amounts than ferulic acid in all these genotypes. Genotypes in the C−1 population exhibited lower dry weight loss as compared to the genotypes in the C+3 population after enzymatic digestion, suggesting changes in cell-wall architecture. Overall, our data highlight the phenotypic plasticity coded by the switchgrass genome and suggest that combining dry matter digestibility with other more specific cell-wall traits could result in genotypes with greater utility as bioenergy feedstocks.

Enzymes have the potential to provide an improved method to ret flax for textile fibers. Retting is the separation or loosening of fiber bundles from the cuticularized epidermis and the woody core cells. New commercial pectinase products were evaluated both with and without ethylenediaminetetraacetic acid (EDTA) for retting efficiency. The Fried Test identified the most efficient enzymes and best retting conditions. All enzymes retted flax stems better in the presence of 18 mM EDTA. Pectinases that also contained cellulases reduced fiber strength, whereas those without cellulases effectively retted flax without substantial strength loss. Viscozyme, which has been used extensively in our enzyme-retting research, and several pectinolytic enzymes were compared in pilot plant scale tests. Texazym BFE and Bioprep 3000 L retted flax as well as Viscozyme in this system, and the fibers had higher tenacity. The monocomponent nature, commercial availability and price, and ability to ret flax in combination with EDTA at high pH indicated a potential advantage for Bioprep 3000 L in these tests. Retting with different enzymes and formulations resulted in fibers with different properties, thereby leading to protocols for tailored fiber characteristics.

There currently are no data on using reduced tillage for flax (Linum usitatissimum L.) production when double-cropped after cotton (Gossypium hirsutum L.) in the southeastern USA. This study evaluated how tillage and subsoiling influenced double-cropped flax and cotton productivity and quality under conditions in the southeastern USA. An irrigated study on a loamy sand soil (Eunola loamy sand) was conducted beginning in spring 2001 through spring 2003. Treatments evaluated in both crops were subsoiling (subsoiled to 30-cm or none) and tillage (chisel plow to 20-cm plus disking, disking only, and no tillage). Standard fiber test methods were used to evaluate treatment effects on fiber properties. Subsoiling increased the cotton and flax yield. Cotton yields were not influenced by tillage treatment while flax dry plant matter yields were greater for chisel and disk treatments compared with the no-tillage treatments. Fiber properties, cotton micronaire, fiber length, and fiber length uniformity, and flax fiber strength were impacted by tillage. Our results indicate that for this double-crop system, no tillage with subsoiling is a viable practice for cotton but further research is needed to improve flax productivity with this management practice.

Flax (Linum usitatissimum L.) is an important commercial crop that supplies both linseed and bast fibers for multiple applications. Retting, which is a microbial process, separates industrially useful bast fibers from non-fiber stem tissues. While several methods (i.e., water- and dew-retting) are used to ret flax, more recently enzymes have been evaluated to replace methods used currently. Alkaline pectate lyase (PL) from the commercial product BioPrep 3000 and ethylenediaminetetraacetic acid (EDTA) from Mayoquest 200 as a calcium chelator were used in various formulations to ret flax stems. Retted stems were then mechanically cleaned through the USDA Flax Fiber Pilot Plant and passed through the Shirley Analyzer. The PL and chelator effectively retted flax from both fiber flax and linseed stems, and the use of enzyme plus chelator retted flax stems better than either component alone. Fiber yield and strength were greater than retting with a mixed-enzyme product that contained cellulases. Retting with PL and chelator was optimized based on fine-fiber yield, remaining shive content, and fiber properties. PL at levels of about 2% of the commercial product for 1h at 55°C followed by treatment with 18mM EDTA for 23–24h at 55°C provided the best fibers based on these criteria. Yield and fiber properties determined by these tests were not improved with PL levels of 5% of the commercial product.

The removal of metal ions from polluted water and wastewater with biodegradable, natural products is an area of current interest in the environmental arena. The objective of this study is to determine whether nonwoven mats made of biodegradable, natural fibers of flax and cotton can be used for remediation of a ubiquitous pollutant of water and wastewater, namely, copper ion. Nonwoven mats manufactured with flax or cotton fiber and flax/cotton fiber blends were treated with citric acid in order to enhance the amount of negative charge on the mats and improve their ability to sequester copper ion. The treated mats were monitored for changes in copper ion adsorption and fabric strength and compared to non-treated mats and process control mats. The results show that mats made from 100% flax and 75%/25% flax/cotton blends were similar to each other and significantly better at copper ion absorption than 100% cotton or 50%/50% flax/cotton blended nonwoven mats. Citric acid treatment, however, diminished mat strength compared to untreated mats for all samples; strength was similar for all treated nonwoven mats after correction for variable mat thickness. Treated flax fiber mats and flax/cotton fiber mats represent a potentially fast and convenient method for removal of metal ions from water and wastewater streams at an approximate cost of $1.40/m2 of mat.

Flax shive constitutes about 70% of the flax stem and has limited use. Because shive is a lignocellulosic by-product, it can potentially be pyrolyzed and activated to produce an activated carbon. The objective of this study was to create an activated carbon from flax shive by chemical activation in order to achieve significant binding of selected divalent cations (cadmium, calcium, copper, magnesium, nickel, zinc). Shive carbons activated by exposure to phosphoric acid and compressed air showed greater binding of cadmium, copper, nickel or zinc than a sulfuric acid-activated flax shive carbon reported in the literature and a commercial, wood-based carbon. Uptake of calcium from a drinking water sample by the shive carbon was similar to commercial drinking water filters that contained cation exchange resins. Magnesium removal by the shive carbon was greater than a commercial drinking water filtration carbon but less than for filters containing cation exchange resins. The results indicate that chemically activated flax shive carbon shows considerable promise as a component in industrial and residential water filtration systems for removal of divalent cations.

Corn ( Zea mays L.) fiber, which is the seed coat and residual endosperm left after grain processing, is a low-value residue that contains carbohydrates and aromatic compounds that could provide value-added coproducts. Treatment of corn fiber with NaOH and assessment by gas chromatography indicated a prevalence of ferulic acid, with about 90% ester-linked in the cell walls. p -Coumaric acid was much lower at about 10% of the amount of ferulic acid. Histochemical reactions employing acid phloroglucinol and diazotized sulfanilic acid indicated the presence of phenolic acids in cell walls of the pericarp and aleurone layer. Various protocols were tested using milled corn fiber and pretreatment with commercial ferulic acid esterases before cellulase treatment, and dry weight loss and sugars and phenolic acids released into the filtrate were evaluated. Ferulic acid esterases effectively degraded corn fiber and released substantial amounts of ferulic acid and sugars (e.g., glucose and xylose) in the incubation medium. Light microscopy showed that ferulic acid esterase substantially disrupted the aleurone layer but caused little visible damage to the lignified pericarp cell walls. Amounts of compounds released varied with protocols, and one study with various milling methods showed that esterase pretreatment followed by cellulase released about 2.8 to 4.4 and 1.5 to 2.9 times more ferulic acid and glucose, respectively, than cellulase alone. The highest levels for one lot of corn fiber with esterase pretreatment followed by cellulase were 3.9 and 218 mg/g of ferulic acid and glucose, respectively.