Tenacity crimping

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. 

Interest in the manufacture of different forms of rayon has resulted in the production of regular rayon, hollow viscose, spun-dyed filaments and staple rayon, crimped rayon and surface modified fibers, high tenacity rayon and high wet modulus (polynosic) rayon fibers. In chemical composition, viscose rayon and cotton are alike they are both cellulose. 

Conventional, low-speed spun fibers must be further finished by drawing, although POY yarns are typically draw texturized. The drawing process adds strength by orientation of the molecular structures. Normal extensibility and proper tenacity are added by drawing the spun fibers to several times their as-spun length. The texturing process produces permanent crimp, loops, coils, or crinkles in the yarn that result in properties of stretch, bulk, absorbency, and improved hand (32). There are three basic types of... 

ASTM D 3217-95 includes the measurement of the breaking tenacity of man-made fibers taken from filament yarns, staple or tow, either crimped or uncrimped and tested in either a double loop or as a strand formed into a single overhand knot."... 

Jute is not a costly fiber but has a high tenacity with low tensile elongation and low crimps, so it is a predominant fiber used for floor coverings, for the base or intermediate layer in tufted floor coverings, for the filling pieces in upholstery, and for acoustic insulating materials. 

Most staple fibers for carpet production have a staple length of 80 to 200 mm, have a round, elliptical, or trilobal cross section, and are heavily crimped. The parameters for drawing, texturing, and setting are set to obtain strong crimp and crimp stability at a low extensional modulus and tenacity (wool type) (Gries et al,... 

The most important testing methods for fibers are the determination of fineness (linear density), crimp, tenacity, elongation, and elastic modulus. The respective testing results often vary considerably. Hence, in many cases, a large number of single tests are required to achieve reliable results. Other properties such as density or humidity take-up are constant values and thus only determined once or twice, or the values are taken from published tables. 

Yarns are often characterized by fineness, twist, tenacity, elongation, and crimp. A yarn s thermal behavior and bending properties can also be important for certain applications. For nearly all products made from yarns, the yarn evenness is crucial. The respective testing devices often also determine yarn imperfections (thick and thin places, neps) and hairiness. 

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