Chemical fibers reaction spinning

The distinction between them is made by the technique used for solidification. Melt spinning consists of extruding a molten polymer and into an appropriate medium (gas or liquid), where it is solidified by the transfer of heat. Dry spinning involves the extrusion of a polymer solution into a heated gas, where the solvent is removed and the fiber solidified. Wet spinning represents the extrusion of a polymer solution into a liquid chemical bath. The subsequent solidification takes place by mass transfer. In reaction spinning, a prepolymer (partially reacted material) is extruded into a heated fluid medium, where solidification takes place by chemical reaction. 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

In order to produce carbon fibers from polyacrylonitrile) (PAN) and various pitches, stabilization is essential after the spinning, which consists of a chemical reaction using different oxidizing gases, such as air, oxygen, chlorine, hydrochloric acid vapor, etc. [91]. The stabilized fibers are then... 

Mesophase is susceptible to chemical reactions other than those induced by pyrolysis. Modifications to enhance fusibility or solubility for easier spinning (see Preparation of Mesophase Pitch) and to induce thermosetting for carbonization without deformation are both practical steps in carbon fiber manufacture. 

The development of elastomeric fibers has resulted in a variant of wet spinning called reaction or chemical spinning. In point of fact, rayon, the first wet-spun material, might properly be said to be produced by reaction wet spinning or chemical wet spinning because complex chemical reactions always have been involved in that operation. In any case, it has been found that the prepolymer of an elastomeric fiber may be extruded into a bath containing a highly reactive diamine so that the chemical conversion from liquid to solid occurs there. 

Sulfar fibers are extruded from polyphenylene sulfide) or PPS by the melt-spinning process. The first PPS polymer was made in 1897 by the Friedel-Crafts reaction of sulfur and benzene. Researchers at Dow Chemical, in the early 1950s, succeeded in producing high-molecular weight linear PPS by means of the Ullmann condensation of alkali metal salts of p-bromothiophenol. 

Extruders are in common use for the processing of polymers, as in the spinning of synthetic fibers. They are also used for the extrusion cooking of foods, such as ready-to-eat breakfast cereals. They are not part of the standard equipment of the usual chemical laboratory, yet they offer considerable promise for running reactions without solvent on a continuous basis. 

Radicals, generated in polypropylene fibers during irradiation as well as the transition frcan these reidicals (R ) to peroxy radicals (ROa ) are monitored by electron spin resonance spectroscopy. Experimental data exhibit an anomaly in the temperature dependence of RO, concentration, around the glassy transition temperature (Tq). The dependence of RO, concentration on temperature, around T, is described by a Hil-liam-Landel-Perry equation rather than by an Arrhenius one. Consequently, the transition consists of two steps the first is associated with diffusion processes and the second with the proper chemical reaction. 

Diffusion is a principal mechanism by which material transfer, necessary for the reactions between the viscose and spin-bath components, occurs [171]. Conditions affecting diffusion will influence the rates at which the various chemical reactions proceed within the forming fiber. Consequently, the extent of reaction at any given time after extrusion will vary across the filament diameter. 

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