Fibres cross-sectional shape

Virtually every fibre, both namral and manufactured, has been used in absorbent nonwoven structures. Being the structural element, fibres making up a nonwoven have a major influence on the absorbency characteristics. The major fibre properties exerting such an influence include polymer type, linear density or denier, fibre cross-section shape, crimp, fibre finish and fine stmcture. 

Matsudaira, M., Tan, Y, Kondo, Y, 1993. Effect of fibre cross-sectional shape on mechanical properties and handle. J. Text. Inst. 84 (3), 376-386. 

The fibre geometry is determined by the production conditions. The linear density and fibre length can be controlled with sufficient accuracy the know-how for controlling fibre cross-sectional shape and fibre distortion (curvature) is well established. 

Arthur et al.54 have shown that cotton modified by AN grafting retains the structure and appearance of the initial fibre (particularly the transverse cross-section shape) much better if the grafted polymer is located in the surface layer. To this end, they suggest graft polymerization to cotton pre-irradiated in an inert atmosphere and the use of solvents causing no swelling of the fibre. 

Figure 9-5. Seven successive stages of change in the cross-sectional shape of a cotton fibre as produced during mercerization.

As it will be shown below, it is difficult to match the correct iy-FVF using a simple representation of yam geometry. In general practice, a certain freedom for an interplay of o-FVF and iy-FVF is deemed acceptable yam volume is generally taken lower to allow for simpler yam cross-section shapes, and the iy-FVF is then increased to compensate for discrepancy in the o-FVF. There is a natural constraint to this approach yams have a fibre packing limit. 

Melamine fibres are primarily known for their inherent thermal resistance and outstanding heat blocking capability in direct flame applications. This high stability is due to the cross-linked nature of the polymer and the low thermal conductivity of melamine resin. The dielectric properties and its cross-sectional shape and distribution make melamine ideal for high temperature filtration applications. It is sometimes blended with aramid or other high strength fibres to increase final fabric strength. 

In addition, the external cross-sectional shape must be rectangular with width 250 mm and depth up to 40 mm, and the weight should be as low as possible. It is proposed to manufacture the new product as an extruded hollow box section, reinforced if necessary by longitudinal webs (see the box section in Figure 8.16). The chosen material is short glass-fibre reinforced polypropylene (GF-PP) with properties given below. 

Purthermore, the presence of some impurities on the surface of the okra fibre can also be seen, and the fibres are cemented in non-cellulosic compounds. In particular, the cross-sectional shape of okra fibre shows a polygonal shape that varies notably from irregular shape to reasonably circular, as depicted in Pig. 1.15. Their diameter considerably vary in the range of about 40-180 pm. Purthermore, each ultimate cell is roughly polygonal in shape, with a central hole, or lumen like other natural plant fibres, as shown in Pig. 1.15. The cell wall thickness and lumen diameter vary typically between 1-10 pm and 0.1-20 pm, respectively. As a consequence of it. 

For example, most of the tensile strength and stiffness data quoted for natural silks are inaccurate. Silks typically have a highly non-uniform cross-section, due to the nonconstant linear production rate of the fibre under natural spinning conditions, and the fact that spinneret orifice sizes can be changed continuously by the spider or larva unless the animal is anaesthetised. Here, non-uniform refers both to the cross-sectional shape, which does not have a simple outline, and to the fact that this shape and its enclosed area can vary with position along the fibre (Dunaway, 1994 Dunaway et al., 1995a ... 

Similar filtration efficiency benefits may be obtained by applying a layer of fibres with irregular or multi-lobed cross-sectional shape as, for a given count, these also provide a greater surface filtration area. P84 is such a fibre, and is often used where superior particle capture is required. 

In dust collection there is an ever-increasing demand for more stringent control of atmospheric pollutants. Improved media performance will be necessary in order to meet these demands and in conventional dust collection it is expected to see greater use of finer fibres, and fibres of irregular cross-sectional shape, applied in the form of surface layers as previously described. Taken to a higher level, PTFE membranes provide the ultimate in particle collection, and the trend to wider use of this material will almost certainly continue, together with further developments to enhance its toughness and durability. 

E. Karaca, N. Kahraman, S. Omeroglu, B. Becerir, Effects of fiber cross sectional shape and weave pattern on thermal comfort properties of polyester woven fabrics. Fibres Text. East. Eur. 3(92) (20) (2012) 67-72. 

The APC materials typically nsed for on-site rehabilitation of timber and concrete are composed of glass, carbon or aramid fibres and a polyester, epoxy or polynrethane polymeric matrix. Glass fibres are the most frequently used due to their moderate cost and good mechanical properties when compared to carbon fibres. They are used normally in the form of pultruded profiles or strips, fabrics (tissues) or mats. Carbon fibres are mainly used in the form of pultruded profiles of solid, open or hollow cross-sectional shapes. While in timber applications both thermoplastic and thermosetting matrix types are used, in concrete applications only the latter type is used. 

Images of material structures may be analyzed at full scale as obtained from polished faces or from cross-sections of specimens. Also, images obtained by means of all types of microscopes may be analyzed. The main objective of the analysis is the quantification of images. This means that, in an observed field, particular objects like grains, fibre cross-sections, cracks and voids are distinguished and quantified as to their area fraction, shape, perimeters, distribution, and so on. 

Many other properties have to be considered, especially for apparel fibres, e.g. moisture absorption, dyeability, drape, texture, weaving characteristics, etc. Many of the properties are strongly influenced by cross-sectional shape cotton is a round hollow fibre, whereas silk has a triangular shape giving it a fine lustre and rustle. Wool has a scaly surface and appears to be made up of two components which have different water absorption characteristics. This gives wool its crimpability and bulk. From studies like these, synthetic fibres can minimic natural fibres and can, in some cases, be more versatile. For example ... 

Microfibers, such as Cyphrex microfibers, are usually less than 5 pm in fibre size, have high surface-area-to-mass ratio, and offer a narrow diameter distribution. They are made from various polymers including polyester, polyamide, and PP. They not only have smaller fibre diameters, but also have various unique fibre cross sections, such as round, flat and wedge shapes. 

Other comments Current techniques are associated with processing undesirabie residues such as soivents, sait particies Equipment cost is high. Controi over porosity is aiways questionabie Shapes are limited Limited to tubular or uniform cross-sectional shapes Limited by the low bending properties of current biodegradable fibres... 

In science and engineering, the tensile properties, such as Young s modulus and tensile strength, are expressed in terms of stress a, i.e. the appropriate load (F) divided by the cross-sectional area of the specimen under zero load ( Iq). Accurate determination of the fibre cross-sectional area is difficult and, for fibres of complex cross-sectional shapes (see Section 14.7), it is practically impossible. 

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