Commercial Drawing Processes

As noted in Fig. 14.1 (a), commercial fibers of semicrystallme polymers are always cold-drawn after spinning to achieve further structuring through further macromolecular orientation and crystalline morphological changes, many of which are retained because of the low temperature of the cold-drawing processes. A typical stress-strain curve for a polycrystalline polymer at a temperature Tg < T < Tm appears in Fig. 14.6. 

From the work context window, the user may activate design tools for operating on the documents contained in the workspace. Here, the user invokes a flowsheet editor [21] in order to insert reaction alternatives into the flowsheet for the Polyamide-6 process. The flowsheet editor, which was also developed in the IMPROVE project, is based on MS Visio, a commercial drawing tool, which was integrated with the PRIME process engine [371]. 

Chapter 3(57) discusses the reduced permeability commonly observed when crystallinity is added to either a rubbery or glassy matrix. The reduction in permeability results from reductions in both the solubility and diffusivity parameters (58-62). This chapter also reviews the important effects of combined orientation and crystallinity which are dependent on whether orientation occurs during the formation of the barrier, or subsequent to it in a cold drawing process (62-66). The effects of process-induced orientation of several commercial barrier resins is considered in further detail in Chapter 12(67). 

Thermal shrinkage force or thermally induced contraction is critical to many commercial operations, such as tire production, transmission belts, and certain types of conveyor belting and is dependent on the annealing and drawing processes during filament manufacture,... 

Commercial wire drawing processes produce metal wires with round cross sections but they are highly energy and labor intensive. Wire drawing falls outside the scope of this book. Commercial rapid solidification processes yield amorphous metallic ribbons. Inviscid melt spinning yields metal fibers by a chemically assisted jet stabilization process. 

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. 

One of the limitations of the curtain-slot draw process has been that the amount of fiber attenuation is constrained because of the short distance generally allowed between the spinnerette and the venturi slot, and the use of relatively low pressure air for drawing so as not to induce high turbulence in the area of the laydown. In order to adapt this concept for the production of polyester fabrics that inherently require much higher fiber acceleration to attain the desired polyester fiber properties, a new process has been commercialized (25). 

PEN mnltifilament fibers are commercially available from several polyester fiber prodncers. These include Teijin in Japan, Honeywell (formally AlliedSignal) in the United States and Enrope, Kosa in Europe, and Hyosimg in Korea. PEN fibers are produced in a melt spinning/post-drawing process similar to that used in PET fiber manufacture. All production to date is in the form of continuous multifilament yarn, although staple and monofilament fabrication have also been reported. 

Oriented polymer films that are prepared by either rolling, rolling and annealing, or some commercial one-way draw processes, may possess orthorhombic rather than transversely isotropic symmetry. For such films, the elastic behaviour is specified by nine independent elastic constants. Choose the initial drawing or rolling direction as the 3 axis for a system of rectangular Cartesian coordinates the 1 axis to lie in the plane of the film and the 2 axis normal to the plane of the film (Figure 8.2). The compliance matrix is... 

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