Natural fiber dimensions

Due to different species, a natural variability within species, and differences in climates and growing seasons, natural fiber dimensions as well as physical and mechanical performance can be highly variable. Methods of producing fibers with more reproducible properties are a major research effort [14]. 

Fiber dimensions have been studied for hemodialysis. When blood is circulated through the fiber lumen (m vivo), a significant reduction in apparent blood viscosity may occur if the flow-path diameter is below 100 p.m (11). Therefore, current dialy2ers use fibers with internal diameters of 180—250 p.m to obtain the maximum surface area within a safe range (see Dialysis). The relationship between the fiber cross section and the blood cells is shown in Figure 5. In many industrial appUcations, where the bore fluid is dialy2ed under elevated pressure (>200 kPa or 2 atm), fibers may burst at points of imperfection. Failure of this nature is especially likely for asymmetric fibers that display a large number of macro voids within the walls. 

In a previous section, data and plots were given showing the rapid rise in consumption and production of manufactured fibers at the expense of natural fibers. The principal reason for this has been the wide range of manufactured fiber variants that can be produced from a single fiber-forming polymer. The wide range of polymers available, each with its particular properties, adds yet another dimension. This is not to say that there is only one type of cotton, wool, silk, or asbestos fiber there are many varieties of natural fibers, but their supply is limited by natural factors such as climate and genetics. The relative availabilities of manufactured fiber types can be altered by controlled chemical-process... 

Penetration of Capillaries in Natural Fibers. The maximum dimensions of cellulolytic enzyme molecules listed in Table V are all smaller than the gross capillaries of both wood and cotton fibers. Thus,... 

Natural fibers can be classified as seed fibers (such as cotton), bast fibers (like flax, hemp, jute, kenaf, ramie), hard fibers (like sisal), fi-uit fibers (like coir), and wood fibers. The chemical composition and dimensions of some common agro-fibers are presented in Table 5.21. The origin of wood fibers can be sawmill chips, sawdust, wood flour or powder, cutter shavings, pulp or wood residues. As binders for these fibers, both thermosetting (like phenolic, epoxy, polyester) resins and thermosetting matrices [such as polyethylene (LDPE, HDPE), polypropylene (PP), poly(vinyl chloride) (PVC), polystyrene (PS)j can be used. Thermoplastic composites are, however, less expensive to process than thermosetting composites, in addition to their ability to be manufactured into complex shapes. 

Quality of various types of materials, particularly of fibers, for their use in various applications is checked by their mechanical properties, which may also throw light on the defects in the fibers. It is well known now that many factors such as morphological structure, fiber dimensions, and its fracture mechanism contribute to the tensile behavior of the fiber. Whether the fiber is of synthetic or natural origin, the defects are supposed to be responsible for the large scatter in their properties. In both these type of fibers, there will be inherent defects related to internal structure-morphological factor. Moreover, one should also expect the existence of defects caused by the processing/extraction process, mainly in the case of namral fibers, which may be distributed nonuniformly and difficult to quantify. These are... 

A.S. Singha, and R.K. Rana, Natural fiber reinforced polystyrene composites Effect of fiber loading, fiber dimensions and surface modification on mechanical properties. Mater. Des. 41,289-297 (2012). 

Polymers for use in biotextiles should possess three specific properties. The first is their ability to be spun. This is the most important characteristic for the production of fibers. The second property is their elasticity. This is fundamental when a variation of the shape and/or the dimension of the DDS is required during its application. The final property is their biocompatibility. Tliis is vitally important for the preparation of oral DDSs, implantable DDSs, etc. Fibers for TDDSs are derived from all types of filament-forming polymers and natural fibers, and because of this they are used ex v/vo. A number of other factors must be taken into account, including how polymers influence a drug s properties, drug delivery routes and desired drug release profiles. ... 

Natural fibers vary widely in chemical composition, stmcture, and dimension and are obtained from different parts of the plants. Natural fibers, such as jute, ramie, flax, kenaf, and hemp are obtained from the stem abaca, sisal, banana and pineapple from the leaf cotton, coir, and kapok from the seed grass, and reed fibers (com, rice, and wheat) [4]. Climatic conditions, age, and fiber extraction... 

Xu, X.W. and Jayaraman, K., An image-processing system for the measurement of the dimensions of natural fiber cross-section, J. Comput. Appl. Technol, 34 (2), 115-121 (2009). 

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