Fiber spool

Fig. 1. A, hoUow-fiber spool B, hoUow-fiber cartridge employed ia hemodialysis C, cartridge identical to item B demonstrating high packing density D, hoUow-fiber assembly employed for tissue ceU growth E, hoUow-fiber bundle potted at its ends to be inserted into a cartridge or employed ia a situation...

Continuous fibers Continuous strands of fibers, generally, available as wound fiber spools. 

Twist in the yarn Most yams have filaments that are twisted. The main reason for this is that an untwisted yam is difficult to weave or knit. Two types of twists can be given to the yam, a counterclockwise twist or S twist and a clockwise twist or a Z twist. Figure 2.1 shows these twists. We can also make a ply yam by using reverse twist directions. This serves to balance out residual stresses. We can also twist together two or more plies to make a cord. Commonly, yam designation on a fiber spool provides information such as name, linear density, number of fibers and fiber type. 

Figure 5 Relaxation of microbending losses and coating modulus for an optical fiber spooled under tension.

Prior to packaging, the fiber is shrink wrapped and weighed. It is convenient for these latter stages to be handled by a computer, which will organize the printing of labels for the fiber spools, apply bar codes, print labels for the inner and outer packages and produce all the requisite paper work. 

A flat plate collector is the most used to collect the fibers. It may be a metal plate such as a sheet or screen [25]. There are methods that use a rotating cylinder to collect the fibers [26]. A fiber spool can be obtained if the angular velocity of the cylinder is combined with the speed of fiber emission. Usually the random behavior of the jet whipping limits the ability of the fibers aligning completely, causing twists and overlaps. 

Simple equipment with provision for wide selection of accurate ratios of carriage-to-mandrel speeds. Powerful machine and many spools of fiber required for large mandrel. 

We use the spinning process to make polymer fibers and filaments that can be converted into fabrics and cordage. During fiber spinning, molten polymer is pumped through holes in a plate to form a multiplicity of strands that are rapidly stretched and cooled. The finished product comprising oriented fibers is either wound up on spools or converted directly into a non-woven fabric. 

Poly[5-(alkylamino)borazines] 7-10 exhibited suitable viscoelastic and thermal stabilities to be extruded in the molten state through the monohole spinneret of a lab-scale melt-spinning apparatus. Thus, an extruded filament (diameter, 200 gm) was drawn with a windup unit, that is, a graphite spool. This provided green fibers with a wide range of diameters (16 =s (f> =s 50 gm Table 2), depending on polymer architecture. 

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. 

Fibers emerging from the spinneret are cooled under controlled conditions, passing over guides and rollers to a take-up spool or bobbin. Often a finish is applied before windup to control static electricity and friction (Stevens 1993). Large-scale production machinery produces fiber at a rate of thousands of feet a minute. A schematic diagram of a melt-spinning apparatus is drawn in Figure 8-10. 

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