Dry spinning of synthetic polymer fibers

New Jersey Institute of Technology, USA, R. M. C. HOGAN, Omni Tech International, USA and M. JAFFE, New Jersey Institute of Technology, USA 

Key words solvent spinning, polymer solution, vapor pressure, skin-core, solvent diffusion through filament wall, dogbone, cellulose acetate, cellulose triacetate, acrylic, spandex, polybenzimidazole, polyvinylchloride. 

There are three major methods for producing polymeric fibers  

The different processes for melt, dry, and wet spinning are shown in Fig. 10.1. Most commercial synthetic fibers are produced by the melt spinning process, which is a relatively simple and low-cost technique compared to wet or dry spinning. However, for polymers without a stable melt phase, spinning 

Dry spinning is used when the polymer is vulnerable to thermal degradation, cannot form thermally stable or viscous melts, or when specific surface 

---

The importance of some of these process issues relating to polymer solution rheology and solidification can be seen in the dry spinning of acrylics (Cox, 2005). An acrylic fiber is one in which the fiber-forming substance is any long chain synthetic polymer composed of at least 85% by weight of acrylonitrile (AN) units (-CH2-CH(CN)-). Acrylic fibers are made from the polymer polyacrylonitrile (PAN), a synthetic, semicrystalline, organic polymer... 

Synthetic fibers, the subject of this article, are produced from linear synthetic polymers by different spinning processes. Depending on whether the process is based on polymer melt or polymer solution, the processes are divided into dry or wet spinning. 

Polymers that demand special precautions during drying are common in the synthetic fiber industry. Of these, nylon and polyester chips are the two most common examples. These resins are hygroscopic and have to be dried before a spinning or molding process. Generally, these polymers are introduced to the dryer in the form of 3 -mm pellets. 

---