Fiber formation spinning methods

The physical properties of the polymer often dictate the spinning method that must be used for fiber formation. For example, if the melt temperature is above the thermal degradation temperature, the polymers cannot be melt spun. Such polymers must be liquified with... 

For fiber formation from a polymer, it is necessary for the polymer to either melt at an elevated temperature or dissolve in a solvent. The first commercially produced PVC fiber (monofilament) was made by a method of melt-spinning [144]. However, melt-spinning of PVC is not an agreeable process because of its high melting point, its high melt viscosity, and its low thermal stability. 

Cross Section. The cross-section structure of mesophase-pitch carbon fibers is one of the four types shown in Fig. 8.12 and is determined by the spinning method, the temperature of stabilization, and the partial pressure of oxygen.The formation of a skin-core structure or skin effect is often observed. This structure is similar to that of the PAN-based carbon fiber shown In Fig. 8.8 above. 

Melt spinning is the least complex of the methods. The polymer from which the fiber is made is melted and then forced through a spinneret and into air to cause solidification and fiber formation. 

Often fibers in textile substrates are deficient in one or more properties, or improved properties are desired for the substrate. Textile finishing provides a method whereby deficiencies in the textile can be corrected or specific properties can be introduced. Physical finishing techniques (dry finishing processes) or chemical finishing methods (wet finishing) are used. Physical finishing is usually carried out on the yarn or formed textile substrate, whereas chemical finishes can be added to the spinning bath prior to fiber formation for man-made fibers or appl ied to individual fibers, yarns, or completed textile structures. 

Dry spinning is also the method of choice for several other polymers including spandex, polyvinyl chloride (PVC) and polybenzimidazole (PBI). These polymers share the characteristic of thermally degrading prior to/during melting and solubility in high volatility solvents. In all cases it is the cost-effectiveness of dry spinning that leads to its adoption as the fiber formation method of choice. 

Although there are many variations on how carbon fibers are made, the typical process starts with the formation of PAN fibers from a conventional suspension or solution polymerization process between a mixture of acrylonitrile plastic powder with another plastic, such as methyl acrylate or methyl methacrylate, and a catalyst. The product is then spun into fibers, with the use of different methods, in order to be able to achieve the internal atomic structure of the fiber. After this, the fibers are washed and stretched to the desired fiber diameter. This step is sometimes called "spinning" and is also vital in order to align the molecules inside the fiber and thus provide a good basis for the formation of firmly bonded carbon crystals after carbonization [7]. 

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