Fiber Formation Process

Many processing parameters affect the stmcture of melt-spun fibers. The most important processing parameters are  

Mass flow rate through each spiimeret hole. 

During melt spinning, these parameters must be carefully controlled so the desired stmcture and properties can be achieved for melt-spun fibers. To understand how to control these processing parameters, an engineering analysis of the 

---

Manufactured fibers produced from natural organic polymers are either regenerated or derivative. A regenerated fiber is one which is formed when a natural polymer or its chemical derivative is dissolved and extmded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber-formation process. A derivative fiber is one which is formed when a chemical derivative of the natural polymer is prepared, dissolved, and extmded as a continuous filament, and the chemical nature of the derivative is retained after the fiber-formation process. 

FIGURE 10 Current asymmetric hollow-fiber formation process for gas separation membranes. 

Fig. 1.6 Schematic of fiber formation process for conventional and liquid crystalline polymers. (From Calundann and Jaffe [26], Hoechst Celanese Research Company.)...

Reviews of specimen preparation methods for fiber microscopy and instrumental techniques applied to fibers were published during the early 1970s [14-16]. This section contains applications of microscopy to the understanding of fiber microstructures used in the industrial laboratory for modification of fiber formation processes to... 

During the fiber formation process, a surface layer was formed on the outermost surface of the solution when the solution was passed through the spiimeret holes into the water bath The solvent diffused from the inside of the fiber and the surface layer further coagulated toward the same point. The rate of diffusion was dependent... 

The general idea [211] that the polymer undergoes stress-induced orientation (SIO) and crystallization (SIC) has been used for a long time to guide the conventional fiber formation process. However, it seems insufficient to further improve the process. 

As stated in the previous section, achieving control over the orientation of electrospun fibers is an important step towards many of their potential applications. However, if one considers the fact that fiber formation occurs at very high rates (several hundreds of meters of fiber per second) and that the fiber formation process coincides with a very complicated three-dimensional whipping of the polymer jet (caused by electrostatic bending instability), it becomes clear that controlling the orientation of fibers formed by electrospinning is no simple task [94]. 

Synthetic fibers typically are semiciystalline. During the fiber formation process, the polymer chains change their conformations to form the crystalline phase. After the fiber formation, the polymer chains in the crystalline phase are largely in trans conformations, which remain unchanged until the crystalline stmcture is damaged or altered. However, in the amorphous phase, the polymer chains still can change their conformations after the fiber formatioiL For example, the... 

The structures discussed above are just examples that can be found in mar synthetic fibers. Fiber scientists now can manipulate the fiber formation processes to obtain a wide range of stractures for different applications. Therefore, other crystalline morphologies and models exist for synthetic fibers. 

---