Crimped staple fibers

Superior resilience found in crimped staple fiber products such as fiberfill, coupled with the natural wicking performance of the fiber are added features, which further enhance the scope of opportunities for PLA. Since this moisture wicking behavior is inherent to the fiber and achieved without the use of finishes this behavior should not decrease over time. Independent testing indicates the wicking behavior of untreated PLA fibers is superior to either untreated or treated polyester fibers. Laboratory UV resistance testing using a Xenon Arc indicates that in comparison with polyester and acrylic fibers, PLA fabrics have superior strength retention than polyester and far superior resistance to discoloration than acrylics. 

Whether or not it is obtained depends on the washing mechanism allowing the shrinkage, and hence the crimp, to develop prior to the completion of regeneration. Crimp development only occurs fiiUy in staple fiber processes where the sluicing operation allows the cut tufts of acid tow to expand freely in ample volumes of hot Hquor. 

Process conditions that favor chemical crimp formation are similar to those used for improved tenacity staple (2inc/modifier route). However, spin bath temperature should be as high as possible (ca 60°C) and the spin-bath acid as low as possible (ca 7%). Attempts have been made to overcome some of the leanness of high strength rayons by increasing the crimp levels. ITT Rayonier developed the Prim a crimped HWM fiber (36) and made the process available to their customers. Avtex developed Avdl 111. Neither remain in production. 

Cross-sectional modifications of a more extreme nature than skin-bursting, which nevertheless do not form crimp, have grown in importance since the early 1980s. These yield a permanent bulk increase which can be translated into bulky fabrics without the need for special care. The first commercial staple fiber of this type was Courtaulds hoUow Viloft, developed in the 1970s using a carbonate inflation technique (37). 

Lubricant for synthetic and natural staple fiber, softness to harsh or high crimp staple. 

ASTM D 3937 provides a method for determining the crimp frequency of synthetic staple fibers, but the between-laboratory variation is known to be great. It is, however, suitable for in-house QC operations. 

Crimp frequency is defined in ASTM D 3937 as "in man-made staple fibers, the number of crimps or waves per unit length of extended or straightened fiber." Compare this with the Textile Institute definition given above. 

ASTM D 3937-90 provides a method for determining the crimp frequency of manmade staple fiber irrespective of how the crimp was inserted or developed. Equivalent ISO and BS methods are not available. 

ASTM D 3937 94 Test method for crimp frequency of man-made staple fibers. 

The demands of staple fiber are different from those of filament yarns. Staple fiber is a continuous filament cut into short lengths in centimeters. Staple fibers are discontinuous and are crimped and chopped to the desired staple fiber length to blend at the carding stage with cotton (short staple), wool (long staple), or other natural fibers. The raw polyester fibers are... 

---