Synthetic staple fiber production

A significant percentage of U.S. synthetic staple fiber production is packaged in bales of extrusion coated spunbonded fabrics, so treated to render the fabric impervious. Synthetic fibers have been shipped worldwide in this manner with great success. 

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. 

Paper-based processes Synthetic staple fibers as well as wood pulp libers are suspended in water and then formed into a paper-like nonwoven web on a perforated surface. The web is then bonded by interlocking the fibers by mechanical or chemical bonding techniques. Fabrics made by this type of process are known as wet-laid nonwovens. Such products can be made at very high speeds and are very uniform, but the process is capital-intensive. 

In 1994, the proportion of PET fibers in the world production of synthetic fibers was 62.9% and of chemical fibers was 55.3%, while in the total volume of all kinds of fibers it was 27.4%. Out of PET fibers presently produced, 38% are staple fibers and 52.5% are filament yarns, with a marked tendency toward an increase in the latter. A 55% proportion is anticipated in the year 2000, At present, about 75% of PET fibers are used for textile purposes and 25% for nontextile purposes. 

Melt or solution spinning of synthetic fibers is a marvel of modern technology. Fiber lubrication, which is of the utmost importance in this high-speed process, is achieved by the application of spin finish—a combination of oils and surfactants. A typical spin line for the production of polyester staple fiber is shown schematically in Figure 2. The number of filaments, which can vary from tens to thousands, come into contact with various parts of the machinery, some of which are heated for proper fiber modification. To replenish the lost finish and to ensure adequate lubrication,... 

The most important application of nylons is in production of synthetic fibers. Nylon fibers are largely produced in the form of continuous filament yam and staple fiber. Since fibers should simultaneously possess crystallization and... 

Even when crimp is fully developed it is easy to pull out (low energy) and difficult to translate into noticeably bulkier woven and knitted fabrics. It does however improve the absorbency and the cohesion of the staple (important in spun-yarn and nonwoven making) and gives a subtly different texture to woven fabrics. Coarse crimped rayon was the leading synthetic carpet fiber in Europe in the 1960s, but has since been replaced by the highly durable bulked continuous filament nylon yams. Crimp is most important in rayon used for hygienic absorbent products. 

Pig. 10. World fiber production in 20th centry cf Cotton Usage— Log Scale. —Cellulosic filament cellulosic staple -x- synthetic filament -a- synthetic staple, cotton. 

Hot and cold methods are also used to create synthetic fibers. A strand of fiber is a single filament that can be combined or spun with other filaments to create the final fiber product. The process from raw polymer to final product is called spinning, as illustrated in Figures 13.39 and 13.40. The cross-sectional shape of the strands is dictated by the shape of the orifice through which is it extruded. As shown in Figure 13.39, extruded fibers are spun together into a filament (bundle of fibers) that can be cut into smaller staple fibers with lengths on the order of centimeters or less that may be further processed into textile materials. ... 

A yam spim from fibers is called a fiber yarn (Figure 17.1a), whereas a yam containing endless filaments is called a filament yam (Figure 17.1b). It seems logical that all synthetic yams would be filament yams, but this is not the case. Filaments are often cut into (short) staple fibers at the end of their spinning process, and then spun again into a fiber yam, either as a blend with cotton or wool, or in a fully synthetic product. The reason is that the fibrous character of a yam is preferred in many textile applications, and that it is difficult to imitate these tactile properties by treatment of filament yams. 

Controlled mechanical film-to-fiber separation, performed by a needle roller equipped with teeth, by embossing or profiling techniques, or by slicing or cutting techniques. In these cases, more or less well-defined separation into regular network-like fibrous structures is achieved. Because of their relatively good uniformity, these processes compete with conventionally synthetic products (coarse multifilament yarns or staple fibers), and one should speak here of slit-film fibers or slit fibers [157]. 

It is very difficult to define the exact worldwide production capacity for bicomponent fibers. Most machines are extruder fed, and many machines in Asia were made locally and are not always successful in making good products. Also, many machines that have bicomponent capability are used to run standard homopolymer products. However, it is estimated that approximately 2-3% of worldwide synthetic fiber production equipment has bicomponent capacity. Of this capacity, approximately 23% for filament yams, 31 % for staple yarns, and 46% for spunbond. Approximately 75% of bicomponent fibers go to a nonwoven end use. 

To date, synthetic fibers retain a great part of the textile market with an annual production of 30 million tons, which represents 60% of the totality of textile fibers this dominant position is due not only to their excellent characteristics and performances but also, for the majority of them, to their low production cost. The improvement brought about by the textile industry to the manufacturing processes of these fibers, along with the facile transformation of raw polymeric materials into filaments or into staple fibers of variable length to eventually obtain fabrics or nonwoven materials of high performance, is the main reason for the success of synthetic fibers. 

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination. 

In 1981, about one third of the total polypropylene usage was based on conventional staple and multifilament products about 60 KT (thousand tons) of ST and 54.5 KT of multifilament yarn. The largest textile end-use of polypropylene was in carpet backing, which was made primarily from ribbon yams. By 1995, its production surpassed aliphatic polyamides (PA) and polyacrylonitrile (PAN), but lagged behind PET. In 2002, the production of polyester fiber was 62%, polypropylene fiber, 17.5%, polyamide fiber, 11.5%, and polyacrylonitrile, 18.1%i, of all synthetic fibers. 

FIGURE 12.53 U.S. production of synthetic fiber staple and tow showing the relative quantities of acrylic fiber produced compared to nylon, polyester, and polyolefin. Acrylic production peaked in the late 1970s. One of the major factors was the decline of the acrylic carpet market, now dominated by nylon. (From Manufactured Fiber Producer Handbook, 1996 Fiber Organon, February 1997, Fiber Economics Bureau, pub.)... 

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