Polymer commercial fiber-forming

The principal forms of spinning are listed in Table 11-1, together with the phase-transformation process as well as the principal commercial fibers formed by each technique. Generally, the selection of a particular type of spinning process is related to the material being spun. For example, nylons are semicrystalline in the solid state and have a definite melting point. Whereas the nature of solid nylon makes it difficult to put it into a solution, it does not prevent a melt from being formed. Hence, nylon is a melt-spun fiber. On the other hand, polyacrylonitrile is an amorphous solid and, as such, is dissolved more readily than a semicrystalline polymer. Here, the result is that polyacrylonitrile is either dry-... 

Spinnerette Process. The basic spinning process is similar to the production of continuous filament yams and utilizes similar extmder conditions for a given polymer (17). Fibers are formed as the molten polymer exits the >100 tiny holes (ca 0.2 mm) of each spinnerette where it is quenched by chilled air. Because a key objective of the process is to produce a relatively wide (eg, 3 m) web, individual spinnerettes are placed side by side in order that sufficient fibers be generated across the width. This entire grouping of spinnerettes is often called a block or bank, and in commercial production it is common for two or more blocks to be used in tandem in order to increase the coverage and uniformity of laydown of the fibers in the web. 

An important direct use of phosgene is in the preparation of polymers. Polycarbonate is the most significant and commercially valuable material (see Polycarbonates). However, the use of phosgene has been described for other polymer systems, eg, fiber-forming polymeric polyketones and polyureas (90,91). 

Nonetheless a few commercially successful noncellulosic membrane materials were developed. Polyamide membranes in particular were developed by several groups. Aliphatic polyamides have low rejections and modest fluxes, but aromatic polyamide membranes were successfully developed by Toray [25], Chemstrad (Monsanto) [26] and Permasep (Du Pont) [27], all in hollow fiber form. These membranes have good seawater salt rejections of up to 99.5 %, but the fluxes are low, in the 1 to 3 gal/ft2 day range. The Permasep membrane, in hollow fine fiber form to overcome the low water permeability problems, was produced under the names B-10 and B-15 for seawater desalination plants until the year 2000. The structure of the Permasep B-15 polymer is shown in Figure 5.7. Polyamide membranes, like interfacial composite membranes, are susceptible to degradation by chlorine because of their amide bonds. 

This work has demonstrated that we have been successful in extruding fibers from these polymer nanocomposites, knit them into textiles, and test their flammability. These prototype nanocomposite FR fiber-forming polymers and textile materials based upon them could be taken forward by interested parties for scale-up and commercial development. 

Polyolefins. Polyolefin fibers are produced from the polymerization of ethylene or propylene gas. The catalysis research of Ziegler and Natta led to the development of these polymers to form crystalline polymers of high molecular weight. Hercules Inc. produced the first commercial fibers in 1961. The fibers made from these polymers are melt-spun. The cross-sections are round, and the fibers are smooth. They have extremely low dye affinity and moisture absorbance. Colored fiber is normally produced by mixing pigments in the melt polymer prior to extrusion. 

Solution viscosities are involved in quality control of a number of commercial polymers. Production of poly(vinyl chloride) polymers is usually monitored in terms of relative viscosity (tj/tjo) while that of some fiber forming species is related to IV [inherent viscosity, c ln(> /)/ )]. The magnitudes of these parameters depends primarily on the choices of concentration and solvent and to some extent on the solution temperature. There is no general agreement on these experimental conditions and comparison of such data from di I ferent manufacturers is not always straightforward. 

Ooly(thiol esters) have been known for more than 25 years as stable, fiber-forming polymers for a brief review see Goethals (I). Still, they have attracted little attention among scientists and have not been produced on a commercial scale. In this article, we summarize these often incomplete results to get a better understanding of this class of polymers. 

There have been several attempts to produce fibers without the use of the conventional extruding and spinneret devices. In electrostatic spinning, for example, an electrostatic field is used to form the polymer into fiber strands (33). This method holds promise, but will require significant development before commercial application can be achieved. 

A large number of commercially important condensation polymers are employed as homopolymers. These include those polymers that depend on crystallinity for their major applications, such as rylons and fiber-forming polyesters, and the bulk of such important thermosetting materials like phenolics and urea-formaldehyde resins. In many applications, condensation polymers are used as copolymers. For example, fast-setting phenolic adhesives are resorcinol-modified, while melamine has sometimes been incorporated into the urea-formaldehyde resin structure to enhance its stability. Copolyesters find application in a fairly broad spectrum of end uses. 

Commercially Important Aramid of Fiber-Forming Polymers... 

If one assumes the total production is a single 5 denier per filament (dpf) ( 20 pm in diameter) filament, the total length would be about 0.01 light years ( 10 " m) or the equivalent of about one million trips to the moon. While other polyesters are commercially produced in fiber form—poly(ethylene naphthalate) (PEN) poly(butylene terephthalate) (PBT) poly(propylene terephthalate) (PPT) and poly(lactic acid) (PLA) thermotropic polyester (liquid crystalline polymer (LCP)—these are of insignificant volume compared to PET. Hence this chapter focuses primarily on PET. 

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