536regain, the prehistory of the fabric before the change of moisture regain, and fiber fineness. The effect of the fineness is demonstrated in Figure 1. The difference between the minimum value and the equilibrium value of the wrinkling angle (deformation time 60 min, recovery time 20 min) was less for the coarse wool ( 10° ) than the difference between the corresponding values obtained with the Merino wool fabric (30°). Fig. 1. Wrinkling angle vs steeping time before deformation.The dynamic fiber rigidity modulus varies in the same way with the above mentioned factors ; hence, the fiber properties are probably of the greatest importance for the wrinkling behavior of wool fabrics, and the results of the experiments may be taken to support the hypothe-. . _ sis about the dependence of wrinkling behavior on the change of rigidity. It is, in fact, highly probable that the same hypothesis holds also for other hygroscopic fibers [1,7]. To improve the wrinkling properties for a given structure of a wool fabric, the sensitivity of the fibers to changes in moisture regain must be diminished. One possible method would be cross-linking reactions. It is, therefore, interesting to observe that Katz [3] found a reduted wrinkling after a treatment with mercuric acetate. ' A method for characterizing the yarn strength potential of cotton by the use of a single parameter is de-scribed~ this method was used to construct reference tables for the skein breaking strength of a wide range of yarn numbers, twists, and cotton quality levels.The prodtiction of a uniform, coherent yarn is the prime essential of a textile staple fiber ; without this quality, it has only limited use. The spinning of fibers into yarns is a craft that has its roots in empirical tradttion. Spinners choose their cottons largely on their suitability for processing, with few end breaks, into yarns of acceptable breaking-strength levels. Before control of spinning quality can be obtained, means must be available for fixing a fiber quality level in a quantitative way, so that fibers can be chosen and modified intelligently. I Cotton spinning laboratories throughout the world spin cotton yarns using only a twist level that gives maximum yarn strength. These results, while valuable, are of little help to those interested in the strength of other yarn constructions, such as the low-twisted knitting yarns or yarns used for weaving into industrial fabrics. Data on groups of cotton varieties remain little more than a mass of facts, giving guidance, but no rules for the .improvement of cotton quality.F. T. Peirce [1] first suggested a method for analysis of yarn strength when he proposed the correlation of yarn strength with three parameters. A thorough description of the contribution of any fiber to the strength of its yarns can be obtained by the application of four 1 Bogdan's Yarn Strength Tables, PB174212, Federal

Four parameters characterizing spinning quality are described and determined for a set of yarn strength data by a method developed from one which was first proposed by F. T. Peirce. The skein break of any yarn number at any twist can be calculated for any fiber if these four parameters are known.

An analytical approach has been adopted to predict the amount of bulk that would develop in a hicomponent fiber having particular geometric distribution of the components of known physical properties. Theoretical expressions have been developed to predict the geometry and mechanical properties of bicomponent struc tures. In particular, an analytical relation has been developed for the radius of the loop of such a structure in terms of strains in the components and their physical dimensions and elastic moduli. The radius of the loop has been related to the bulk ratio. Expressions have also been derived to predict the load elongation relation for the coiled bicomponent structure

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A method based on a modification of the "nearest neighbor" relationship, as used in ecology, is developed for evaluating the extent of mixing of nonhomogeneous fibers in a blended yarn. The evaluation parameter is the degree of randomness in the radial fiber dispersion of a yarn. Simulated cross sections are created for study in such a manner that they feature either randomness or some imposed form of nonrandomness. The procedure for applying the method and the manner of evaluating its results are explained in detail. The method of computation has been programmed so that it can be per formed on a computer.