Fibers processing

Fiber grade PTT typically has an IV of 0.80-1.00 dL/g. The IV value might seem high when compared to the typical 0.64 dL/g IV fiber grade PET. Since IV is unique to each polymer, one cannot compare tire IV values of two different polymers. A 0.92 dL/g IV PTT has a similar molecular weight of an 0.64 IV PET witli a Myf of about 40 000. 

PTT polymer pellets must be dried to a moisture level of 30 ppm, preferably in a close-loop hot air dryer, to avoid hydrolytic degradation during melt processing. Drying is canied out widi 130°C hot air witli a dew point of —40°C for at least 4h. Because of tire faster ciystallization rate, PTT pellets are already semicrystalline after pelletizing, and do not require pre-crystallization prior to drying as with PET. The dried polymer is extruded at 250-270 °C into bulk continuous filaments (BCFs), partially oriented yarn (POY), spin-draw yarn (SDY) and staple fiber. 

1 Partially Oriented and Textured Yarns for Textile Applications 

PTT POY yams were textured by the false-twist method at 140 to 160 °C. Crimp development was almost twice as high as PET, with crimp contraction reaching about 50 %. When PTT yams with a high level of crimp contraction are knitted into stretch fabrics, the amount of stretch achieved is equivalent to PET stretch fabrics incorporated with 6 to 8 % of Spandex [89], In addition to stretch, PTT fabrics tend to have softer hand and better drape than PET. Since they do not absorb moisture like nylon, PTT fabrics also have a desirable dry touch and comfort. 

In Section 19.12, it was pointed out that the cross section of fibers is determined by the cross section of the spinnerette holes and the nature of the spinning process. This plays an important role in establishing the properties of the fiber. For certain applications, the spun fibers are textured after spinning. Carpet fibers, for example, are often given a heat-set twist and/or are crimped by passing them through a pair of gear-like rollers. 

Poly(ethylene terephthalate) Cellulose Poly(acrylonitrile) Poly(vinyl alcohol) Poly(styrene) 

In addition, fibers are classified according to their origin into natural and man-made fibers. Natural fibers can come from vegetable, animal, or mineral sources. Man-made fibers include regenerated and completely synthesized fibers. 

All presently used vegetable fibers are cellulosic (cotton, flax, hemp, ramie, jute, sisal), and all presently used animal fibers are proteins (wool, natural silk, camel hair). Asbestos is a mineral fiber. 

Regenerated fibers are fibers produced from material of natural origin. The material undergoes some chemical process or modification (viscose silk, acetate silk, nitrocellulose, alginate fibers, etc.). Synthesized fibers are synthetic fibers completely synthesized from other raw materials. 

In addition, fibers are classified according to application into textile and industrial fibers (see also Section 12.3.6). Textile fibers are used for yarn, weaves, knitted fabrics, etc., and industrial fibers are used for filter cloths, ropes, etc. 

Fundamental Principles of Polymeric Materials, Third Edition. Christopher S. Brazel and Stephen L. Rosen. 2012 John Wiley Sons, Inc. Published 2012 by John Wiley Sons, Inc. 

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Electrical Behavior. The resistivity of acetate varies significantly with humidity with typical values ranging from 10 ohm-cm at 45% rh to 10 ohm-cm at 95% rh (16). Because of the high resistivity both acetate and triacetate yams readily develop static charges and an antistatic finish is usually apphed to aid in fiber processing. Both yams have also been used for electrical insulation after lubricants and other finishing agents are removed. 

The equipment for the slit-film fiber process is shown in Figure 15 (29). An olefin film is cast, and as in melt spinning, the morphology and composition of the film determine the processing characteristics. Fibers may be produced by cutting or slitting the film, or by chemomechanical fibrillation. 

The second ceUulosic fiber process to be commercialized was invented by L. H. Despeissis (4) in 1890 and involved the direct dissolution of cotton fiber in ammoniacal copper oxide Uquor. This solvent had been developed by M. E. Schweizer in 1857 (5). The cuprammonium solution of ceUulose was spun into water, with dilute sulfuric acid being used to neutralize the ammonia and precipitate the ceUulose fibers. H. Pauly and co-workers (6) improved on the Despeissis patent, and a German company, Vereinigte Glanstoff Eabriken, was formed to exploit the technology. In 1901, Dr. Thiele at J. P. Bemberg developed an improved stretch-spinning system, the descendants of which survive today. 

High Tena.city Sta.ple Fibers. When stronger staple fibers became marketable, the tire yam processes were adapted to suit the high productivity staple fiber processes. Improved staple fibers use a variant of the mixed modifier approach to reach 0.26 N /tex (3 gf/den). The full 0.4 N /tex (4.5 gf/den) potential of the chemistry is uimecessary for the target end uses and difficult to achieve on the regular staple production systems. 

Whether or not it is obtained depends on the washing mechanism allowing the shrinkage, and hence the crimp, to develop prior to the completion of regeneration. Crimp development only occurs fiiUy in staple fiber processes where the sluicing operation allows the cut tufts of acid tow to expand freely in ample volumes of hot Hquor. 

Work on other routes to ceUulosic fibers continues, driven by a desire to identify an environmentally benign route to ceUulosic fibers that can utilize the large capital investment in the xanthate route and hence cost less than a completely new fiber process. 

The Courtaulds Tencel Process. The increasing costs of reducing the environmental impact of the viscose process coupled with the increasing likelihood that the newer cellulose solvents would be capable of yielding a commercially viable fiber process led Courtaulds Research to embark on a systematic search for a new fiber process in the late 1970s. 

Textile technology is used to mechanically or aerodynamicaHy arrange textile fibers into preferentially oriented webs. Fabrics produced by these systems are referred to as dry-laid nonwovens. Dry-laid nonwovens are manufactured with machinery associated with staple fiber processing, such as cards and gametts, which are designed to manipulate preformed fibers in the dry state. Also included in this category are nonwovens made from filaments in the form of tow, and fabrics composed of staple fibers and stitching filaments or yams, ie, stitchbonded nonwovens. 

Nonwoven Cards. Modem, high speed cards designed to produce nonwoven webs show evidence of either a cotton or wool fiber-processing heritage and have processing rate capabiUties comparable to those of gametts. Contemporary nonwoven cards are available in widths up to 5 m and are configured with one or two main cylinders, roUer or stationary tops, one or two doffers, or various combinations of these principal components. 

J. E. Netdes, Handbook of Chemical Specialties Textile Fiber Processing, Preparation, and B leaching,] ohxs Wiley Sons, Inc., New York, 1983, pp. 391—457. 

Fig. 4. Process flow diagrams for (a) PAN-based and (b) pitch-based carbon fiber processes.

The precursor fiber is subsequently washed and stretched to the low tex (denier) required for carbon fiber processing. Stretching also imparts considerable orientation to the polymer molecules and provides the basis for the highly oriented carbon stmcture that forms after carbonization. Special care is taken to avoid contamination or impurities that may form strength reducing flaws in the carbon fiber. 

Taconite-ore-processing plants Glass-fiber-processing plants Charcoal-production plants ... 

Wallenberger, F. T., et al., Advanced Inorganic Fibers Processes, Structures, Properties, Applications, Kluwer, 1999. 

The process flowsheet for a cellulose acetate fibers process is shown in Figure 19.12. Solvent is removed from the fibers in a dryer by recirculating air. The air is cooled before it enters an absorber where the solvent is absorbed in water. The solvent-water mixture is separated in a distillation column and... 

Schwarz M (2000) Design of recycled fiber processes for different paper and board grades. In Gottsching L, Pakarinen H (eds) Recyled fiber and Deinking. Fapet Oy, Helsinki (Chap. 6)... 

New process modifications have been developed for the conventional dry grind corn process such as quick germ (Singh and Eckhoff, 1996, 1997) and quick fiber processes (Singh et al., 1999b Wahjudi et al., 2000). These... 

Wahjudi, J., Xu, L., Wang, P., Singh, V., Buriak, P., Rausch, K.D., McAloon, A.J., Tumbleson, M.E., and Eckhoff, S.R. 2000. Quick fiber process Effect of mash temperature, dry solids and residual germ on fiber yield and purity. Cereal Chem. Tl, 640-644. 

Palma istle, 11 296 Palm fibers, processing of, 11 298 Palmitic acid, 22 756 boiling point, 5 53t percentage in selected fats and oils, 2 519t 5 47t... 

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