Three different scouring methods are applied to open-end and ring spun yarns prior to hydrogen peroxide bleaching with and without metal ions present. The scouring procedures include a penetrating treatment with aqueous sodium hydroxide solution, a nonswelling solvent extraction, and a fiber surface-affecting treatment with pectinase enzymes. Properties of the treated yarns and fiber damage are studied after each process step. Conventional scouring with sodium hydroxide followed by peroxide bleaching causes the highest deterioration on the molecular level, but results in a high level of whiteness, Solvent extracted yams exhibit superior tensile strength, which is preserved more or less unchanged throughout any subsequent treatment. The bioscouring process with enzymes renders the yams strikingly soft. The effects are generally more pro nounced for open-end spun yams, suggesting that differences in yarn structure may have an impact on the effectiveness of scouring.
A statistical approach for determining the technological value of a variety of cotton is presented. The approach suggests that the market value of cotton should correspond to its technological value in a particular manufacturing system; that is, the value of a bale of cotton should be determined based on its expected performance in the textile mill and the yarn quality obtained from it. A model relating fiber to yarn properties is a basic requirement for implementing the approach. The procedures used in this approach include developing a multiple regression model relating HVI fiber properties to the desired quality parameter of yarn (skein break factor), determining the percent relative contribution of a fiber property with respect to skein break factor, selecting a reference set of HVI fiber properties, determining a difference factor of the difference in value between fiber properties of a particular variety and the reference set, and finally, developing a premium/discount formula. The main feature of the approach is its flexibility in accommodating different fiber properties and yarns of different counts produced on different spinning systems.The market value of cotton is determined largely by a subjective evaluation of a limited number of quality parameters. Traditionally, three parameters have been considered: grade (comprising trash, color, and preparation ), fiber length, and fiber fineness. The grade is determihed visually by comparing with standard cottons, fiber length is estimated visually, and fiber fineness is estimated instrumentally [ 5 ] .For many years, subjective cotton classing has been used without major conflict between cotton users and producers. This was attributed to three main reasons: the existence of the traditional ring spinning, which made both producers and users quite familiar with the desired quality of raw material; relative market stability; and the lack of rapid and accurate testing methods. I In recent years, the technology of ring spinning has undergone several changes, and new spinning techniques have been developed. A typical spindle speed of today's ring spinning machine is 16,000 rpm, compared to less than 7000 rpm fifty years ago. New spinning technologies such as open-end and air-jet are capable of producing yarn at rates much higher than that of ring spinning. In order to accommodate these mechanical capabilities, fibers must flow individually or in small bundles at very high speeds. They must also withstand the stresses resulting from opening and condensation actions involved in the new spinning technologies. The increased use of synthetic fibers that can be modified to suit a particular spinning technique makes determination of the value of cotton (based on its contributing quality) necessary for efficient blending and better processing performance.Traditional cotton 6ber testing methods are being replaced by high volume instrument (HVI) systems that are capable of providing accurate and rapid measurements of several cotton 6ber properties [ 5, 6 J . The data obtained...
The importance of interfiber friction in determining yarn strength has been acknowledged by several authors. Studies of the effect of friction on yarn strength were often based on determining the influence of twist level, a structural factor, to change the level of friction. To our knowledge, no study is available in which varying fiber frictional characteristics are introduced into a constant yarn structure ( i.e., the same twist, fiber type, fiber length, etc.). This effect has been accomplished through a surface treatment that changes the level of interfiber friction, and subsequent yarn testing provides useful and interesting information about how fiber interaction contributes to yarn strength. The results presented here show that interfiber friction can (under certain circumstances) be the dominant factor in determining the tensile properties of a ring spun staple yarn. Friction and yarn strength results show that moderate changes in the interfiber friction can produce large changes in yarn strength. We suggest that interfiber friction should receive more attention as a determinant of yarn properties, particularly strength.
This study presents a new approach for characterizing the frictional behavior of cotton fibers. Fiber-to-fiber or fiber-to-metal friction is determined over length increments of a fiber fringe, each containing a different number of contacting fibers. The total sliding distance corresponds to the maximum fiber length in the sample. The resulting relationship between frictional force and sliding distance is termed the "friction profile" of fibers, and it can be used to determine the frictional force corresponding to a certain fiber intensity. The nonlinear nature of this profile is represented by an equation of the form F = a o ( n f ) 2(1-n ) , where n f is an estimated value of the number of contacting fibers, F is the frictional force, and a o and n are friction indexes. Using the principle of the fiber friction profile, a measuring technique is described for measuring both fiber/ fiber and fiber/metal friction parameters. This technique is believed to simulate fiber friction in both processing and deformation modes. Although friction in this study was measured only for cotton, other kinds of staple fibers (natural or synthetic) can also be tested.
An advanced statistical procedure for developing reliable prediction equations relating cotton fiber properties and the skein break factor of yarn is demonstrated. The procedure consists of a sequential analysis in which subsets of independent variables are obtained by linear regression to best predict a dependent variable. Selection of the most reliable equation is based on three main criteria: the R2 statistic, the Cp statistic, and the MSE. The independent variables considered in the analysis are the cotton fiber properties measured by the HVI system (MCI3000). A reliable regression equation relating cotton fiber properties and yarn quality should simultaneously satisfy the two criteria: it has a high R2 value and uses only the most important fiber properties. Written primarily for textile scientists and engineers, the details of the statistical analysis are minimized, and the analysis is presented in its proper context, as a useful tool for the nonstatistician.
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