Four Forms

• Filament and staple are the most widely manufactured forms, followed by tow and fiberfill. Filament form has continuous strands that produce smooth fabrics. Strands for staple are cut to short lengths, used mostly for blending with other fibers. Continuous filaments are drawn loosely together to produce tow. Fiberfill produces voluminous fibers used in quilts, pillows and outerwear.
  
  

Polymerization and Spinning

• Constituent acids and alcohols, which are derived from the base polymer, are heated in a vacuum to 472°F. The molten polyester is extruded into long ribbons, cooled until those ribbons become brittle, cut into chips and completely dried.
  
  Chips are placed into hoppers for melting at 500 to 518°F, giving them a syrupy consistency. This solution is extruded through spinnerets. The shapes and numbers of holes determine the size and fiber of the resulting yarn, which are brought together to form a single strand.
  
  

Drawing

• Emerging from the spinneret, the polyester fibers are stretched while still hot to reduce their width and increase their strength, tenacity and resilience. This process allows the fibers to become solid and strong instead of brittle. Following drawing, the fiber is wound on large bobbins.
  
  

Staple

• The process for staple is similar to that for filament, except the spinneret has many more holes with resulting thick, rope-like bundles. The fibers are drawn, crimped and then cut into shorter lengths after their second heating.
  
  

Variations

• Several different treatments can affect the resulting fiber. A delusterant can make the fiber semi-dull or dull. Spinnerets commonly have circular holes, but square, oval, bean-shaped or even hollow fibers may be formed. Adding dye at a critical time in the process can produce brilliant colors. Crimping or texturizing can give the fiber more bulk as well as increase its insulation abilities.
  
  

Yarns

• Before it can be woven into fabric, the fiber is made into yarn via filament or spun method. Polyester filaments are grouped together and twisted to make them workable. Spun polyester is made in a similar manner to cotton or wool yarns. Long filaments are cut into short pieces then spun together to create yarn.
  
  

Weaving and Finishing

• Polyester yarns may be either woven or knitted. A number of finishing processes are often used to improve the fabric. Singeing improves the hand, reduces pilling and increases smoothness. Water and stain repellents may be added, while resins may be applied to aid fabric care.