Filament cold-drawn

Such fibers can be produced, for example, as a copolymer composed from 80% ethene and 20% acrylic acid is extruded through a spin-nerette die into a 500 p diameter strand at 125°C and then drawn to a 10 ju diameter filament. The filament contains an orientation resembling to a cold-drawn filament (9). After several intermediate steps, eventually microporous chopped fibers are obtained that are useful as intermediates for forming high melting aluminum salt derivative fibers. This is effected by contacting the fibers with an aqueous solution of 0.5% aluminum sulfate. 

The uniform oxidation of the cold-drawn filament results in a high overall degree of oxidation and associated backbone scission before surface deterioration reaches the level at which spontaneous restructuring and crack formation can occur. Lateral cohesion of these fibers was much greater than for the highly oriented filaments. For example, the latter could be easily peeled, whereas the cold-drawn fiber stretched rather than fibrillated after notching. 

The incorporation of P-1 into monofilament by compounding with PPH powder and extrusion was effective only partially in reducing draw-initiated oxidation. After X3 cold draw (at 25°C) the observed -OOH level was 0.3 X 10 3M, in the presence of 0.1 wt % P-1, in comparison with 1.1 X 10 3M for the stabilizer-free fiber. Furthermore, this lower level of draw-induced degradation still had a large photosensitizing effect, even in the presence of the stabilizer. After 200 hr of UV exposure in the xenon arc, the P-1 concentration was reduced by more than 20 fold in the cold-drawn filament and photooxidation was accelerating rapidly, whereas for the undrawn filament no P-1 loss was visible, and photooxidation was undetectable. 

Figure 1-26. Flowchart showing steps in the manufacture of nylon 6, 6. facture of nylon 6,6. Specific amounts of the two chemicals are combined in solution to form nylon salt. The salt is purified, polymerised, extruded in ribbon form and chipped into small flakes or pellets. The polymer is then melted and extruded through a spinnerette into cool air, where the filaments are formed. The filaments are then stretched or cold drawn to develop desired properties. Nylon staple is obtained by crimping filament tow and then cutting into short uniform lengths.

Laboratory filament (high hot draw) Laboratory filament (medium hot draw) Laboratory filament (low hot draw) Laboratory filament (no hot draw) Laboratory filament (no hot draw, cold drawn X 3) Commercial Film (Enjay)... 

Changes in the residual elongation at break for four filaments of varying draw history are shown in Figure 6. From Figure 6a, which is based on the time taken to halve the initial elongation at break, it is obvious that photosensitivity as measured by embrittlement increases in the sequence highly oriented (hot drawn X6 at 180°), << undrawn partially oriented (hot drawn X2.5 at 180°) << cold drawn (X3 at 25°C). 

Figure 6. Changes in mechanical properties and oxidation products during FPH photooxidation. [OOH] by iodometry. Filaments undrawn (O), partially oriented X3 at 180°C (D), highly oriented X6 at 180°C (A), or cold drawn X3 at 25°C (V). All drawn in air.

Magnetization measurements were made on untwisted composites at the last stage of the drawing process, just before the twisting process. To ensure that the filaments would be in a metallurgical state as close as possible to the one achieved after twisting, the samples were cold drawn to a final diameter the same as that of filaments in a twisted composite. 

Fie/. 3. Polyethylene terephthalate. Variation of increase in birefringence on drawing with draw ratio for filaments cold drawn at different temperatures. ( From Ref. 34.)... 

Structure deduced from the distinct four point pattern observed in samples which were annealed after drawing. For cold drawn polymers the assumption of a single phase structure implicit in the aggregate theory may therefore be valid. Some of the materials to which the aggregate theory has been applied were hot stretched (i.e. drawn above the glass transition temperature), but the annealing in these cases would be far from complete, since the temperature was maintained for a relatively short time, and the filaments were always under tension. Thus again a distinct two phase structure may not have been well developed. 

The variation of compliances with draw ratio for cold drawn polypropylene filaments examined at 20°C appeared very similar to that of high density polyethylene, with an increase in all compliances but Sii, which was insensitive to draw ratio. Ward aggregate theory was not applicable except for low draw ratios, implying that other processes intervened in addition to an orientation of pre-existing units. It was probable that even above the glass transition temperature increasing orientation led to a reduction in molecular mobility, as was known to occur in polyethylene terephthalate. ... 

The resulting nylon 66 or 6 chips are melt-spun into a cooling chamber in which nylon filaments form. In the case of nylon 66, the filaments are run through a steam chamber to wet them before they are wound. This treatment eliminates the undesirable extension of the yarns after they reach equilibrium by absorbing moisture from the air. The wound yarn is further cold-drawn by stretching about 400% in order to acquire better strength. 

Austin suggested organic solvents containing acids such as chloroethanol, sulfuric acid and trichloroacetic acid (TCA) for the direct dissolution of chitin in 1975 [23]. A filament was extmded from the spin solution made with chitin in a mixture of 40% TCA, 40% chloral hydrate, and 20% methylene chloride. The filaments were solidified in the coagulating bath containing acetone, neutralized with potassium hydroxide (KOH) in 2-propanol followed by washing in deionized water, and, then, cold drawn. Other solvent systems for chitin have been proposed [24]. However, they require fairly drastic conditions to dissolve chitin and some are very corrosive or expensive. It is hard to maintain the chitin molecule without depolymerization during the dissolution process. 

The residue from the above is a hard, very tough, opaque, leatherlike mass. It melts (becomes transparent) at 58°-63°C, but at this temperature it is too stiff to flow and shows considerable resistance to deformation. At slightly higher temperatures, it can be drawn out into thin strips or filaments, which can be stretched and cold drawn (see Note b). The product then shows fiber orientation and also exhibits parallel extinction between crossed Nicols. The cold-drawn material is exceedingly strong, tough, and pliable. 

Figure 5.10. WAXS patterus takeu from undrawn (as extruded) and cold drawn samples of neat PP and its blend with PET (a) PP as extruded, (b) PP drawn, (c) PP/PET (73.3/16.7 by wt) spun (textile filament), (d) knitted and compression molded PP/PET (73.3/16.7 by wt) filament followed by annealing at 145°C...

During this cold-drawing process, vegetable oil is applied to the yarn as a lubricant and is washed off afterwards. In the case of nylon 6 melt-spinning is also used. The filaments are normally drawn to 350 00%. If the molecular weight of nylon 6 is between 20 000 and 25 000, hot-drawing is used. Unlike PET, both nylon fibers are fairly crystalline as spun. The crystal structures of nylon 66 and 6 fall into the categories of a, ji and 7. Almost all the commercially important nylons exist in either the a or the /3 form. 

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