Textile Research Journal

A brief description of the stretch-vibrometer developed at the Firestone Research Laboratories is given, and the theory of its operation is outlined. Described are new measurements made on the instrument verifying the previous conclusion that loss of energy to the apparatus is immeasur ably small. Values of the dynamic stretch moduli E, coefficients of internal friction μ, and hyster etic energy losses of 15 samples of natural and synthetic textile materials, Fiberglas, and steel wire are given. Corresponding static values of moduli and energy losses are also given. The latter, it is shown, do not correlate with dynamic values, and hence cannot be regarded as predictive of dynamic behavior. The resonant frequencies at which measurements were made on these samples ranged from 65 to 360 cycles per second.

The significance of the various measures which have been employed with the present data to express hysteretic losses is discussed, and it is shown that the quantity μω ₀/E, while not rigidly constant, is confined to a narrow range of values in most samples. Further evidence is submitted generalizing the near-hyperbolic relationship between μ and ω_o. Results of application of the method to the comparison of various tire-cord rayons are given. Measured on the stretch-vibrom eter have been dynamic moduli ranging from 2.1 × 10 ¹⁰ (rubber thread) to 226 × 10¹⁰ (steel wire) dynes/cm.2, and internal-friction coefficients from 0.74 × 106 (rubber thread) to 25.7 × 106 (silk thread) poises.

Quantitative data on the length and diameter changes accompanying the adsorption of water by human hair are given as functions of the relative humidity. Data are also given on the effects of a load on the swelling isotherms. A theoretical treatment is proposed which accounts in a semi-quantitative way for the swelling isotherms and the effects of tension as well as for the adsorption isotherm.

Many of the methods used to study the fine structure of cellulose are tedious and not suitable for routine use. In the present work, an equilibrium moisture regain method which can be carried out on a large scale with a high degree of accuracy has been developed. The method is illustrated by a wide variety of cellulose materials covering a wide range of moisture sorption capacity. The terms "accessibility" and "crystallinity" are discussed and possible errors arising from assumed equivalence of these terms are pointed out. A preliminary attempt to evaluate both accessibility and crystallinity of cellulose from moisture regain data has been made. This evaluation results in a proposed revision of the scale of reported crystallinities of various types of cellulose.

The hydrolysis method for studying cellulose accessibility has been compared with moisture regain and x-ray diffraction methods. It is proposed that recrystallization of cellulose during hydrolysis is a determining factor in this method and, therefore, that published data obtained from hydrolytic studies should be reconsidered.

The study of the molecular structure of cellulose fibers by x-rays has been concerned until very recently with diffraction of only relatively wide angles. Almost no work has been done on the diffraction and scattering of x-rays within very small angles adjacent to the primary beam. The only fact known was that such "small-angle scattering" is produced by ramie and viscose rayon.

In the present study, the small-angle scattering by various cellulose fibers has been investi gated and it has been found that the scattering by different fibers is completely different.

The hypothesis that the small-angle scattering in cellulose fibers would be related to the micellar size and distance is substantiated by the fact that an experimental change of those distances results in a corresponding (inverse) change in the extent of the scattering. On this basis the difference in the scattering patterns of different fibers is explained as a difference in the size and distance of the cellulose micelles or crystallites.

An orientation of crystallites is also expressed in the small-angle diffraction pattern giving rise to the interesting phenomenon of "cross" formation when the crystallites form an angle with the long axis of the fiber. The angle between the intersecting lines of the cross proved to be related to the pitch of the spiral of the crystallites in the fiber.