Yarn structure

Photodegradation is a topochemical reaction and thus is affected by fabric and yarn structure (16) and by the fineness and cross-sectional shape of the fibers. The faster deteriorating outer layers are believed to have a protecting effect by allowing less radiation to penetrate the interior of the construction (11,16,17). Because of the irregularity of the attack there may be some variability in the fluidity data of the bulk material (11,17). Desai (17) took the thickness of the material into account and measured the DP of the exposed and the unexposed side separately and found considerable differences in the data. 

A fiber yarn is a multifilament assembly. A yarn is frequently employed in making woven forms. There are certain yarn structural parameters that are important in determining its properties. Some of the important yam stmctural parameters are described below. 

Meanwhile Etliicon (and otiiers) developed alternative absorbable surgical sutures, based, for example, on copolymers of polyglycolide with poly-L-lactide or poly(trimethylene carbonate), and on polydioxanone, and on poly(s-oxycaproate), and also on copolymers of tliese with polyglycolide or with each otlier. These different structures made it possible to provide fibres with different rates of absorption, with different degrees of stiffness or flexibility, and for use in monofilaments, braided multifilaments, and other yarn structures, as required for different surgical operations. 

It Is of Interest to point out the Figure 2 spin line capillary diameter effect on the FOY yarn structure, where the 7 mil (0.018 cm) diameter capillary yielded no amorphous orientation change, but a significant crystallinity reduction relative to the 15 mil (0.38 cm) capillary. From the above discussion, the generally equal FOY tensile properties for yarns spun from the two capillaries are predicted from the equal amorphous orientation values at equivalent spinning speeds (Table I). The greatly reduced PTY broken filament count for the yarn textured from the higher crystallinity FOY spun from the 15 mil capillary I also consistent with the above discussion. 

Multi-ply of yarn structures Spontaneous extention by crystallization Natural disorders... 

Grishanov S, Siewe F and Cassidy T (2011), An apphcation of queuing theory to modelling of melange yarns. Part II A method of estimating the fibre migration probabUities and a yarn structure simulation algorithm , Text Res /, 81(8), 798-818. 

Siewe F, Grishanov S, Cassidy T and Banyard G (2009), An appUcation of queuing theory to modelling of melange yarns. Part I A queuing model of melange yarn structure . Text Res J, 79(16), 1467-1485. 

Figure 1 (a) Scanning electron micrograph of an unconsolidated commingled GF/PP bundle (variation 1 with 45vol.% glass fibers presented in smaller diameter), (b) Schematic illustration of different hybrid yarn structures. 

To avoid the development of ad hoc relations, a large experiment, comprising 295 drawn poly(ethylene terephthalate) (PET) yarns, was performed, covering a wide range of yarn structures and properties. This setup offered a unique opportunity to study the structure-property relations very intensively. 

Yoshida, K., Kurose, T., Nakamura, R., Noda, J., and Goda, K., Effect of yarn structure on mechanical properties of natural fiber twisted yarns and green composites reinforced with the twisted yarn, J. Soc. Mater. Sci. Jpn., 61 (2), 111-118 (2012) (in Japanese). 

Rubber fibers are manufactured by several companies as rubber fiber or under trade names such as Buthane, Contro, Hi-Flex, Lactron, Lastex, and Eaton. Rubber fibers show good elastomeric properties and reasonable aesthetic properties particularly as the eore of a textile yarn structure. Rubber fibers usually have a dull luster due to the additives and fillers within the fiber. The fiber has poor resistance to household chemicals. 

Two further improvements to the basic concept were proposed. The first was a broad-based patent based on the development of an open-end spinning technology called aerodynamic break spinning (ABS) but which utilized differential twisting to create a novel yarn structure from staple fibers at very high speeds (claims of potentially 3000 m/min). Within the general claims, there is also the potential to include a filament core (to make a core spun yarn) or to incorporate a filament covered with molten polymer (Bobkowicz, 1976). When viewed against the ICS system, the proposed approach was much more complex and was not commerdalized. 

Idealized yarn structure. Copied from publicity material Spin at 1000 m/min supplied to author by Bobtex International, Leicester, UK. 

Schematics of observed yarn structure. Redrawn from Nichols etal. (1972). 

The cross-section was irregular, often ribbon-Uke, and the staple components were not uniformly distributed, but tended to be concentrated on one side of the polymer. Fig. 8.10 is an illustration of the ideal yarn structure A compared to what was commonly observed B-F. 

Fibers are normally spun into yarns with the exception of nonwovens (Chapter 6). A selection of typical yarn structures is shown in Fig. 1.11. The so-called spun yarns are yarns made from staple fibers (for example cotton and cut man-made fibers). All other yarns are made from man-made fibers. Plied yarns consist of two or more parallel oriented yarns twisted yarns consist of at least two twisted yarns. 

Figure 3.26 presents a comparison of three yarn types with regard to yarn uniformity, twist level, and yarn structure. Table 3.2 shows a comparison of the three most important spinning principles in various characteristics both direct (tenacity, elongation, uniformity, and so on) and indirect (tensile force) parameters were chosen. 

The simulation of yarn structures is a very complex task and hence time consuming and costly. A good overview and detailed descriptions of various aspects is given in Neckaf and Das (2006, 2012). 

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