Fiber fineness how to improve fiber fineness influence of fiber fineness

The property of fineness or coarseness of textile fibers has been recognized as one of the most important all the fiber characteristics affecting processing behavior and yarn properties. Finer and shorter wools are generally regarded as much more valuable to the worsted trade than long and coarse ones. On the other hand, in the cotton industry the importance of fiber fineness is somewhat over shadowed by length considerations, mainly because of the fact that longer fibers are also finer ones.

The stiffness, drape and handle are highly influenced by the bending behavior of fibers, whereas recovery from bending influences creasing. The resistance to bending or flexibility of a fiber depends on its shape, its tensile modulus, its density, and above all, its fineness. For a given yarn linear density or for a given fabric weight made from a given fiber, the resistance to bending increases as the linear density (Fineness) of the fiber increases. Consequently, fiber fineness is an important property in determining the stiffness of a yarn or fabric and eventually its softness, handle, and drapeability qualities.

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In the process of yarn formation, fibers are subjected to the twisting operation. The resistance to twisting of a fiber, its torsional rigidity, is dependent on its shape, density, shear modulus and fineness (diameter). That is for given fiber, the amount of twist required to produce comparable internal stresses, which in turn control the cohesion characteristics and yarn strength, with all other things being equal, will be greater in a yarn composed of coarser fibers than in one composed of fine fibers. This factor is of profound importance when considered in terms of producing highly twisted yarns and sewing threads (snarls, kinks can have detrimental effect on the quality of thread).

Further more, the cohesiveness of fibers in a spun yarn depends on the inter fiber friction (influenced by twist), which in turn is a function of the total of fiber contact (fiber specific surface) and the fiber coefficient of friction. Thus fibers with larger specific surface (finer fibers), all other things being equal, will require less twist compared to those having smaller specific surface (coarse fibers) to prevent slippage in a yarn.

In addition to fiber length, fiber fineness also plays an important role in determining the processing efficiency and spin ability – the optimum yarn size to which the raw material can be spun – of a staple fiber stock. Moreover, the uniformity of a yarn is largely dependent on the average number of fibers in its cross-section. Therefore, for a given yarn linear density, the finer the fibers (meaning  larger number of fibers in a cross-section), the more regular the yarn. It is to be noted that the uniformity characteristics has a considerable influence on such yarn properties as strength, extensibility, appearance, feel, and end breakages in spinning, winding, warping and weaving.

Fabric luster is yet another property that has affected the fineness of fibers, since this determines the number of individual reflecting surfaces per unit area of the fabric. In other words, the fine fibers will produce soft sheen whereas coarse fibers will generate hard glitter.

The rate of dye-uptake by a fiber is also dependent on the total available surface for a given volume of the fiber materials , that is specific surface of the fiber i.e. finer fibers will require less time to exhaust the dye bath than coarse ones which will affect the overall appearance of dyed fabrics.