Synthetic Yarns

Synthetic cellulose yams were developed between 1880 and 1910, first from a nitrocellulose solution, and later as copper rayon and viscose rayon . The cellulosics are often called half-synthetic because the raw material is a natural polymer. The most important fully synthetic yarns were developed between 1935 and 1942 - polyamides (PA66, PAG), polyester (PET), and acrylic yarns (PAN copolymers). Another half-century later, many high-performance fibers were introduced, for example aramid (PPTA), gel-spun polyethylene, and carbon fiber. 

All synthetic yarn processes are continuous, so endless filaments are formed. For filament yams, the spirmeret contains as many holes as the number of filaments required for that particular type of yam. For synthetic staple fiber production, the spirmeret contains thousands of holes and the filaments are cut into fibers at the end of the process. 

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Type of Data In general, statistics deals with two types of data counts and measurements. Counts represent the number of discrete outcomes, such as the number of defective parts in a shipment, the number of lost-time accidents, and so forth. Measurement data are treated as a continuum. For example, the tensile strength of a synthetic yarn theoretically could be measured to any degree of precision. A subtle aspect associated with count and measurement data is that some types of count data can be dealt with through the application of techniques which have been developed for measurement data alone. This abihty is due to the fact that some simphfied measurement statistics sei ve as an excellent approximation for the more tedious count statistics. 

Introduction The following example data are used throughout this subsection to illustrate concepts. Consider, for the purpose of illustration, that five synthetic-yarn samples have been selected randomly from a production line and tested for tensile strength on each of 20 production days. For this, assume that each group of five corresponds to a day, Monday through Friday, for a period of 4 weeks ... 

Application. In the past, the break strength of a synthetic yarn has averaged 34.6 lb. The first-stage draw ratio of the spinning machines has been increased. Production management wants to determine whether the break strength has changed under the new condition. 

Until the mid 20th century only natural textile fibers were generally available, and most garments were made of either wool or cotton. From the 1940s onward natural fibers were more commonly partly replaced by synthetic fibers used either on their own or in mixed natural and synthetic yarn. By the late 20th century natural fiber use had dropped worldwide to approximately 35%. Despite this, cotton remains the most widely used textile fiber (Miller 1992). The second half of the 20th century saw a massive expansion not only in the use of synthetic fibers but also in natural-synthetic fiber mixtures. 

Currently, potentially hundreds of different combinations of natural and synthetic yarns are available to manufacturers to weave or knit into cloth. Early 21st-century clothing comprises a broad mix of purely natural, purely synthetic, and mixed fabrics. Fabric content will influence response of the garment to different depositional environments and will likely lead to differential preservation of the garment sets. The latter half of the 20th century saw the development of unisex clothing items in which the general style and... 

These non-gelling grades have a 98.0-98.8 percent hydrolysis range. Fully hydrolyzed grades are used for sizing spun synthetic yarns and synthetic/natural fiber blends. 

Low friction, non-silicone wax emulsion for natural and synthetic yarns, spun and filament. 

Unique nonionic softener and lubricant for application to natural and synthetic yarns and fabrics. 

Function Removes and stops static and electro-static charges on all types of soft surfaced polyethylenes, linear, polyethylenes, fabrics, textile fabrics, natural and synthetic yarns and all types of carpets and carpeting. 

Cloth A type of woven filter septum made from natural or synthetic yarns. 

The quick-drying and crease-shedding properties of the synthetic yarns made domestic laundering much easier and eliminated the need for ironing. This created a demand for cellulosic goods with similar characteristics, and this was met by the so-called easy-care finishes. It will be apparent from the properties listed under (i), (vi), and (ix) that crease-resistant finishes can be adapted for drip-dry or wash-and-wear products. Mercerization or, better still, tension-free treatment with caustic soda before padding opens up the structure of the fibre and facilitates the entry of the precondensate. 

New England Rayon Synthetic Yarns Peddlers Association, Providence, R. I. Earl V. Litchfield, president. 

Mauersberger, H. R., Technical Report on New Synthetic Yarns, Fabrics, and Finishes, ... 

The dimensional stabUity of synthetic yarns and textiles can be considerably enhanced by a thermosetting process, i.e. heat treatment under dry heat, steam or hot water. Thermosetting may be undertaken either with or without applied tension. Thermally treated filament yarns and staple fibres show less heat shrinkage, have a reduced tendency to crimp and show improved recovery from creasing. 

Table 10.4 Characteristics of Synthetic Yarns Used in Commercial Fishing Gear"...

Various techniques, such as x-ray diffraction, fiber density, dyeing or dye rate methods, and thermal methods of analysis, used to estimate the heat history and heatset temperature of synthetic yarns are not suitable for routine quality control/process control because of the time and extensive sample preparation required to perform the test. Therefore, NIR methodology offers a simple, rapid, and accurate technique for measuring the heatset temperature of carpet yarns. 

Most natural fibers have a non-round cross-section and low luster (Figure 17.2) silk is the exception. Moreover, yams spun from these fibers have a high volume (bulk) and fiber ends make them hairy. All these factors are appreciated for applications in textiles and carpets. Synthetic yarn is most easily spun from round spinning holes, the filament yams have a high luster, they are flat (not textured), and hairiness is absent. This may be perfect for industrial yarn applications, but it is not desirable for most textile and all carpet yams. 

The optimization of the functional properties of a synthetic yarn (in particular from the point of view of its mechanical behaviour) requires maximum orientation of the macromolecules in the direction of flow. This objective can be difficult to achieve because of the generally pseudoplastic behaviour of such liquids. Tlie dies which the polymers cross typically have the shape of a funnel (see Rg. 2.6). When the macromolecules are brought into liquid state in the system, they will undergo stresses because of the irregularity of the die s diameter. Under the action of the pressures at the exit of the extm-sion device, the polymer will cross successively three zones in the die (see Fig. 2.6). The advance of the macromolecules from Zone I towards Zone II shows that the flow rate will increase because the section of the capillary... 

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