PET Staple Fiber

Most textile filament yarns are also direct-spun. The output per bundle is small, and therefore hundreds of spinning positions must be fed from one polymerization unit, making the polymer melt-line system very complicated. Winders make four, six, eight, or even 12 packages simultaneously, and spinnerets and spinning pumps are clustered accordingly. 

Partly oriented yarn (POY) is a large product spun at about 3500 m min with a round cross-section, and draw-textured (DR 1.8, at about 1000 m min ) in a separate step. Fully oriented yarn (FOY) can be spun at 6000 m min or drawn in the spin-line (hot-tube spinning, HTS), or spin-drawn. Typical yarn titers are 30, 50, 76, 110, and 176 dtex, and the filament titers 2-3 dtex, although there is a trend toward values of 1 dtex or lower. 

Direct spinning is not very common for industrial yarns because there are only a few yarn types that would match the large capacity of polymerization units ( 25 000 ton y ). A further complication is that the polymer must be condensed to a high molecular weight, but this can be achieved in deep-vacuum, thin-film finishers . In most cases chips with a textile viscosity are solid-state postcon-densed, at a relatively low temperature (about 230°C), which takes many hours but has the advantage that thermal degradation is minimized. 

There is a limited field of application for low yarn titers, 200-550 dtex, in sewing yarns and fine fabrics. Most industrial yarns have titers of 1100-2200 dtex. The filament titer is usually around 5 dtex, but yams for safety belts have coarser filaments (10-15 dtex) and modern tire yarns may have finer filaments (around 3 dtex). 

Large spinning holes (350-800 pm) are used to handle the high melt viscosities. 

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Non-crystalline polymers or copolymers can also be used to generate fibers with relatively low softening temperatures. Such fibers can be blended with regular fibers, e.g. staples, and bonded together by applying sufficient heat to melt the low-temperature component. Such fibers need not be exotic. The use of undrawn, amorphous fibers suffices for many such purposes, for example, bonded nonwo-ven webs formed from a mix of drawn and undrawn PET staple fibers. Without crystalline structure, the undrawn fibers will soften and become tacky at relatively low temperatures, so providing bond sites. 

This study was supported by NIOSH Grant No. 5 R01 OH 00744-03 and by Cotton Incorporated, "nie authors are grateful for this assistance and for the materials supplied by the following companies Cotton Incorporated (cotton) Fiber Industries Inc. (Portrel pet staple fiber) Texaco, Inc. (Texspray Compound) Vickers Sons, Ltd. (Spraycot 8853) ICI Americas, Inc. 

PET staple fiber, filaments, non-wovens (Section 6.11.3), insulating fiber fills, carpets, strapping, sheet, films, non-food contact containers, injection moldings, large moldings, and engineering resins. 

Staple. PET staple is widely used in 100% polyester or cotton-blend fabrics for apparel. Typical cotton-blend polyester staple fibers have a linear... 

Fig. 1. Trends ia staple fiber usage ia nonwoven fabric manufacturiag where is olefin, is PET, and M is rayon.

In 1994, the proportion of PET fibers in the world production of synthetic fibers was 62.9% and of chemical fibers was 55.3%, while in the total volume of all kinds of fibers it was 27.4%. Out of PET fibers presently produced, 38% are staple fibers and 52.5% are filament yarns, with a marked tendency toward an increase in the latter. A 55% proportion is anticipated in the year 2000, At present, about 75% of PET fibers are used for textile purposes and 25% for nontextile purposes. 

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 carried out with 130 °C hot air with a dew point of < -40 °C for at least 4 h. Because of the faster crystallization 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 yam (POY), spin-draw yam (SDY) and staple fiber. 

PET fibers are produced in a variety of forms, broadly classified as staple fibers, textile filament and industrial filament. End-uses for these variants have different requirements in terms of fiber properties and physical geometry, and so different fiber manufacturing processes have evolved according to the special needs of each market segment. 

Unlike nylon, which is highly crystalline, PET fibers are amorphous after spinning. They are like the molecules shown at the top of Figure 22-6 in Chapter 22. In order to make a usable textile yarn or staple fiber our of PET, it must be drawn under conditions that result in orientation and crystallinity. This is accomplished by drawing at temperatures of about 175°F with stretch 300-400%. As with nylon, the conditions of draw (especially... 

Unlike nylon, which in the as-spun state contains a high amount of crystalline component, PET fibers are essentially amorphous as spun. In order to secure a usable textile yam or staple fiber, this product must be drawn under conditions that will result in an increase in both molecular orientation and crystallinity. This is done by drawing at a temperature well above the glass transition point, T, which is about 80°C. Conditions of rate ana temperature must be selected so that the amorphous areas are oriented, and crystallization will take place as the temperature of the drawn... 

Eastman Kodak introduced a new polyester as a staple fiber called Kodel in 1958. A new diol was introduced to derive a patent-free composition of matter a mixture of cis- and trans-1,4- cyclohexanedimethanol made by the exhaustive hydrogenation of dimethyl tereph-thalate. This polyester had a higher Tg than PET and also a higher melting point, but it was successful enough to find a market. In recent years, the polyester has found use in polyester carpets [41,42]. 

Polyester (PET)Zviscose rayon Staple fiber Nonwoven composite... 

Recycling of post-consumer PET bottle waste into Recycled Polyester Staple Fiber (RPSF). 

Eig. 1. Typical stress—strain curves for cotton and PET fibers. A, industrial B, high tenacity, staple C, regular tenacity, filament D, regular tenacity, staple ... 

Terephthahc acid (TA) or dimethyl terephthalate [120-61 -6] (DMT) reacts with ethyleae glycol (2G) to form bis(2-hydroxyethyl) terephthalate [959-26-2] (BHET) which is coadeasatioa polymerized to PET with the elimination of 2G. Moltea polymer is extmded through a die (spinneret) forming filaments that are solidified by air cooling. Combinations of stress, strain, and thermal treatments are appHed to the filaments to orient and crystallize the molecular chains. These steps develop the fiber properties required for specific uses. The two general physical forms of PET fibers are continuous filament and cut staple. 

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