The Evaluation of the Spinning Properties of Man-Made Staple Fibers

A survey is given of the five properties of individual fibers which determine behavior during processing—length, thickness, geometrical structure, surface layer, and the inside structure of the fiber. The geometrical structure consists of three elements: the length structure, the cross-sectional structure, and the surface structure. The existing spinning techniques have been based on length and thickness of the fibers. The complete conversion of fibers into yarns is divided into two main opera tions: those which lead to the formation of a card sliver and those which convert the card sliver into a yarn. The criteria for normal processing on the cotton system and on the worsted system are mentioned and illustrated with some data. The methods used for measurement of these fiber properties are described. They are subdivided into two categories : those by which properties of one fiber are measured and those by which the effect of the interaction of fibers is measured. Special attention is paid to those measuring techniques which have originally been developed in the Textile Research Department of the "Algemene Kunstzijde Unie," viz., equipment for measuring fiber length. linear density, crimp, surface friction, and stiffness (all of individual fibers) and equipment for determining sliver strength and drafting forces for assemblages of fibers. The behavior of fibers during processing is determined by their interactions. For this reason the determination of drafting forces is most effective in studying processing qualities of fibers. It is demonstrated that man-made fibers exhibit relativdy large drafting forces at drafts between 1.2 and 1.8. In this region drafting forces are much larger than those with cotton and probably those with wool fibers. Therefore, in the processing of man-made fibers. "breaking- draft" zones should be avoided. This is illustrated by the improvements brought about by two-line drafting on drawing frames, two-zone drafting on slubbing and roving frames. and elimination of the top-rollers on the back cylinder in the spinning machines of the cotton system when processing rayon polyamide and polyester fibers. A relation exists between the coefficients of friction of a staple fiber, the drafting forces as meas ured on the instrument. and the behavior of fibers during the conversion of slivers into yarns in actual processing.