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Fiber processing solid-state extrusion

Solid-state extrusion has been practiced with coextrusion of different polymers [93]. Despite the large amount of research on solid-state extrusion and the outstanding mechanical properties that can be obtained, there does not seem to be much interest in the polymer industry. The main drawbacks, of course, are that solid-state extrusion is basically a discontinuous process, it cannot be done on conventional polymer processing equipment, and very high pressures are required to achieve solid-state extrusion. Also, one should keep in mind that very good mechanical properties can be obtained by taking a profile (fiber, film, tube, etc.) produced by conventional, con-... [Pg.41]

This section deals with semicrystalline thermoplastics that cannot be processed by the techniques described earlier. Perkins and Porter (22) have reviewed the solid state deformation of polymers in detail and describe the numerous reports of solid state extrusion. Aharoni (23) has reported that a number of polymers may be solid state extruded to high draw ratio (> 10) by the conventional process. These include HOPE, poly(ethylene oxide), poly(4-methyl pentene-1). Polypropylene is also readily extrudable (24). However, there are many other polymers that would be attractive if they could be obtained in high draw, particularly the established fiber-forming polymers such as the nylons and poly(ethylene terephthalate). The ma,ximum extrusion draw ratio that has been reported for nylon 6 is 5 (25). This has been attributed to the onset of strain hardening at much lower extensions than polyethylene (10). Ultrahigh molecular weight polyethylene is also of interest as a way of improving the mechanical properties. [Pg.305]

Polyethylene may be extmded below its melting point if sufficiently high pressures are exerted, in which case the process is known as solid-state extrusion. If the starting material is a reduced entanglement precursor, such as solution-grown crystals [56] or as-polymerized granules [57], fibers and tapes with ultrahigh... [Pg.435]

Poly(ethylene terephthalate) (abbreviated PET or PETE) is a semi-aromatic thermoplastic polyester obtained by condensation reaction of difunctional reactants and well-known for more than 60 years. PET is commonly produced by esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct or by transesterification reaction between ethylene glycol and dimethyl terephthalate with methanol as a byproduct. In order to obtain high molar masses polymers, solid-state polymerization is carried out. PET is one of the most important industrial polymers because of its excellent properties as tensile impact strength, chemical resistance, processability, clarity, thermal stability and others. The main applications of PET are fibers for textiles, films and bottles. Annual world PET production is around 60 millions tons. PET materials were manufactured using extrusion, injection molding and blow molding techniques. [Pg.97]

Technically, chemical fibers are conunonly made by extruding a thick, viscous liquid through a spinneret to form continuous filaments. In this process, the fiber-forming polymers are initially in a solid state and must be converted into a fluid state prior to extrusion. This is usually achieved by melting, if the polymers are thermoplastic, or by dissolving them in a suitable solvent if they are nonthermoplastic. If they cannot be dissolved or melted directly, they must be chemically treated to form soluble or thermoplastic derivatives. [Pg.39]

The actual formation of the fibers and films in a spinning or extrusion process takes place during coagulation of the lyotropic solution. In this process step a phase transition to the solid state is induced by a non-solvent. The conditions of the coagulation process, e.g. the concentration of the polymer solution, the composition and the temperature of... [Pg.310]

The blown film process was briefly described in Section 1.2.6. The process is shown schematically in Figure 10.7. There are many similarities between the blown film and the fiber spinline because of the free surface and the very small transverse dimension relative to the distance between melt extrusion and solidification, and thin sheet equations analogous to the thin filament equations are typically used, although the hoop stress must now be taken into account. The equations for a Newtonian fluid were first published by Pearson and Petrie in 1970, and their approach has been used by nearly all investigators since. There are two steady-state momentum equations because variations in both thickness and width in the stretching direction are important. The mechanics of the solid region above the ill-defined freezeline are... [Pg.161]


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