Multifilament spinning

The metering pumps are precision-made positive-displacement gear pumps, especially designed for melt spinning. They are used to ensure that a precise proportion of the melt from the extruder is delivered to each thread line and that the thread line denier does not vary with time. Modern pressure-feedback-controlled extenders operate remarkably steadily, but not steady enough for multifilament spinning without meter pumps. 

The optimum amount of UV absorber varies with each chemical type and application, but in most cases is in the 0.25-1.0% concentration range. Other factors to consider while selecting the proper type and amount of UV absorber are color contribution, FDA sanction for food packaging applications, and, of course, add-on cost. The UV absorbers are incorporated into plastic substrates by dry blending, extrusion compounding, and then conversion into the final product by various processes such as injection molding, blown film extrusion, multifilament spinning, and sheet extrusion. Also, UV absorber dispersions can be prepared and dyed onto textile fabrics, which will not only UV-stabilize the polsrmer substrate but also improve the color stability of the dyes used to color the fabric. 

In actuality, fiber-spinning processes involve multifilament spinning. Pick one of the treatments of Chapter 11 and extend it to the multifilament case. 

The effect of aerodynamics on drag and heat transfer in multifilament spinning is studied using a computational fluid dynamics code for the air flow in... 

Enzymkette multifilament spinning Multifilamentspinnen, Mehrfadenspinnen multilayer adv/adj mehrschichtig multilayer film Mehrschichtfolie multilayered vielschichtig, mehrschichtig... 

Cross-Winding styie A hollow-hber membrane manufactured via a multifilament spinning process allows element construction with parallel hber arrays or filament winding, that is, cross-layered arrays. This unique fabrication allows regular open spacing between the hollow hbers, which minimizes element pressure drop and assures uniform flow throughout the element. 

Although multifilament effects are important, there are few literature reports on this topic mainly because of the complexities associated with accurately describing the heat transfer and dynamics during multifilament spinning. The interested reader is referred to the original works by Yasuda et al. (1978), Ishihara et al. (1989), and Dutta (1987). 

Braided Synthetic Nonabsorbable Sutures. Braided synthetic nonabsorbable sutures are made by melt-spinning thermoplastic polymers into fine filaments (yams), and braiding them, with or without a core, to form multifilament sutures in a range of sizes. Nylon-6,6 [32131 -17-2] (7) is a polyamide produced by the condensation polymerization of adipic acid and 1,6-hexanediamine. 

Research effort at Albany International Research Co. has developed unit processes necessary for pilot scale production of several species of reverse osmosis hollow fiber composite membranes. These processes include spin-dope preparation, a proprietary apparatus for dry-jet wet-spinning of microporous polysul-fone hollow fibers, coating of these fibers with a variety of permselective materials, bundle winding using multifilament yarns and module assembly. Modules of the membrane identified as Quantro II are in field trial against brackish and seawater feeds. Brackish water rejections of 94+% at a flux of 5-7 gfd at 400 psi have been measured. Seawater rejections of 99+% at 1-2 gfd at 1000 psi have been measured. Membrane use requires sealing of some portion of the fiber bundle for installation in a pressure shell. Much effort has been devoted to identification of potting materials which exhibit satisfactory adhesion to the fiber while... 

A variation on this approach used multifilament coextrusion, so-called microfabrication by coextrusion (MFCX) . A limitation of the single-filament process is the size of the filament. The rheological properties of the polymer/ ceramic blends make spinning fibers smaller than 250 pm very difficult. Additionally, spooling fine-diameter fibers is quite challenging. The MFCX is shown schematically in Fig. 1.3. The setup is the same as that used to spin fibers except that the spinneret is replaced with an extrusion die with a diameter between 1 mm and 6 mm. Two separate extrusion steps are used. In the first step, coarse primary filaments are extruded from the feedrod (Fig. 

Early in the manufacture of PP, a concept was developed for dry spinning directly from the solution obtained in the polymerization operation. Had it been feasible, it would have been the realization of a chemical engineer s dream the gaseous olefin fed into one end of the equipment, and the packaged fiber, ready for shipment to a textile mill, coming out the other end. But it did not turn out that way, and today melt spinning is the accepted technique for the production of staple fibers, monofilament, and multifilament yams. To this usual method have been added the fibrillation and the slit film procedures for producing yams. 

Elastane. The DuPont Company commercialized the first manufactured elastic fiber, Lycra, in 1958. Originally categorized as a span-dex fiber, the name elastane has become more common around the world. This specialty fiber is described as a segmented polyurethane that contains hard and soft segments their ratio determines the amount of stretch built into the fiber. Elastane fibers are formed by dry-spinning or solvent-spinning. The continuous filaments can be coalesced multifilaments or monofilaments, depending on the manufacturer. 

For this comparison, a melt-spinning process was chosen. Each special thermoplastic process influences the structure and thus the properties of the obtained polymer samples differently. This is particularly pronounced for fibers, since especially melt spinning is a process which makes extremely high demands on the deformation ability of the polymer melts at high deformation speeds. Particularly the tensile stress within the fiber formation zone is a very important factor to reach a high orientation of the macromolecules along the fiber axis and a stress-induced crystallization. This crystallization should be discussed in relation to PLA and PHB multifilaments, and at the same time the general property spectrum of these polymers should be represented. 

The results of spin-drawing experiments of both polymers should be compared here for illustration. Polyfilaments have been generated consisting of 12 monofilaments with a respective diameter of 30m at a take-up speed of 2,000 mmin Table 2 shows the textile physical parameters and data of the crystallinity of the PHB and PLA multifilaments. 

The manufacture of all man-made fibers involves at least three distinct process steps. The first consists of the production of polymers or polymer derivatives suitable for spinning into fibers. In the second step, or spinning, a polymer melt or solution is extruded under pressure through the appropriate spinneret s orifice(s) to form the fiber or fibers. If only a single fiber is produced from a spinneret, it is referred to as monofilament. Multifilament spinnerets produce yarns. The third step is drawing,... 

Melt copolymerization requires high temperatures (T > 200 °C). In spite of the six-membered ring it has the extrapolated ceiling temperature T = 1800 °K, well above the decomposition temperature 43). Polyglycolide (mp = 224-226 °C) is converted into multifilament yam by usual melt-spinning and -drawing procedures giving products with tenacities (5-10 g/den) close to polyethyleneterephtalate fibres. 

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