Multifilament yam

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. 

The experiments were carried out by using a prewashed PET-multifilament yam with 32 filaments per bundle and 182.5 dtex. The material has been heat setted at 195°C and was dyed with C02PES MARINE SM1F from Ciba-Geigy (Basle, Switzerland). 

Fibers are frequently used in the form of a yam, mainly because a multifilament yam is more fl ble and pliable than a solid monofilament of the same diameter. The process of making a continuous, multifilament thread or yam from continuous or staple fibers is called spiraling. This nomenclature is rather unfortunate because the same term is also used to denote the process of making individual fibers by extmding through a spinneret. The fibers in a yarn are held in place through radial frictional compressive force generated by the twist that... 

In a multifilament yam or in a braided fabric, normal (i.e. in the radial direction) frictional force holds the fibers together. Such an interfiber friction is desirable if we wish to have strong yams and fabrics. However, there eire situations where we would like to have a smooth fiber surface. For example, in a yam passing round a guide, a smooth fiber surface is desirable. If the fiber surface is... 

Teflon [Du Pont], TM for tetrafluoroethyl-ene (TFE) fluorocarbon polymers available as molding and extrusion powders, aqueous dispersion, film, finishes, and multifilament yam or fiber. The name also applies to fluorinated ethylene-propylene (FEP) resins available in the same forms. The no-stick cookware finishes may be of either type. Fibers are monofilaments made from copolymer of TFE and FEP. 

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. 

Braids BR-V to BR-IX were prepared using multifilament yams of Polymers IX to Xlll, respectively. The BSR data of these braids are summarized in Table 2.6 and indicate that ... 

Benicewicz, B. C., Shalaby S. W., Clemow, A. J. and Oser, Z., In vitro and in vivo degradation of poly(Z-lactide) braided multifilament yams, in Agriculture and Synthetic Polymers, Glass, J. E. and Swift, G., Eds., American Chemical Society, Washington, DC, 1990, chap. 14. 

Greisler and co-workers have examined the use of commercial absorbable fibers for the production of absorbable vascular grafts. Using multifilament yam of 90/10 poly(glycolide-co-/-lactide) and monofilaments of poly-p-diox-anone to produce totally absorbable grafts was shown to be impractical. This is because of the insufficient strength retention profile of these grafts postoperatively. 

These covered yams consist of elastomeric multifilament yam and a covering made from conventional (hard) multifilament yams or fibers such as polyamide, viscose, and so forth (Petmlis, 2004). In this process, the elastomeric fiber, drawn at a constant factor, is fed through a hollow spindle and covered with a covering yam from a flanged bobbin. The produced yam has a particular differential-twist stracture, caused by the different twists and twist directions between the wrapping yam and the core yam. 

Willemsen, S., Weening W.E., and Steenbergen, A., Adhesive-coated multifilament yam of an aromatic polyamide, a yam package, a cord, a fabric, a reinforced object and a process for making said yam, U.S. Patent 4,557,967, December 10, 1985. 

In general, PET with a high tensile strength, and glass, which both appear as multifilament yams, are used for coated membranes. For load-bearing constructions woven fabrics are mostly qualified twisted multifilaments are processed to plain woven fabrics in plain or in panama weave. 

Staple-fibre yams - at least in the weft direction. In operation, the fabric is pulled over a series of rotating rollers termed pile and connter pile , each of which is clothed with card wire and monnted concentrically on a large cylinder of approximately 1.5 m diameter. As the cylinder rotates, the pile rollers raise the fibres proud of the surface, whereas the counter pile rollers stroke them into a more orderly fashion. Raised fabrics may comprise 100% staple-fibre yams or a combination of multifilament and staple-fibre yams, the latter being woven in satin style in which the face side is predominantly multifilament yams and the reverse side predominantly of staple-fibre yams. The smooth surface provided by the multifilaments will aid cake release, whilst the raised staple-fibre yams on the reverse side will enhance the particle collection efficiency. A significant measure of the width contraction invariably takes place during this operation and proper attention will have to be given to this when designing the fabric. 

In practice, the manufacturers of multifilament yams produce a number of standard linear densities that, for industrial filtration purposes, may range in fineness from 120 decitex to 2200 decitex, with individual filaments varying from 6 to 10 decilex. From this, it can be shown that the diameter of such filaments will be of the order of 0.03 mm. 

Staple fibre aramid yams are produced by reducing a continuous multifilament yam to a bundle of staple fibres by means of steetch breaking and then spinning them into a yam using the ring spinning system. 

Most technical yams for reinforcement are based on continuous multifilament yams having linear densities typically in the 1100 dtex (1000 denier) region in singles or doubled configurations. The number of filaments per yam will vary between about 140 and 200 for melt-spun nylon 6.6 and polyester to >500 for high tenacity viscose and other wet-spun fibres, including the aramids. For instance, Kevlar 29, suitable for rubber reinforcement, is available as a 1670 dtex yam with 1000 filaments. "... 

It could be shown that die formadon of different crystal phases is possible with inline drawing of PVDF multifilament yams. 

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