Structure a
Y Q
EARL E. BERICLEY AivD THOMAS KERR’ IJ. S . Department of Agriculture, Beltsville. M d . unorganized or poorly organized regioiln designated as LLrnorphous substance. Goldfinger, Mark, and Siggi:t ( 8 ) , Sickcrson (Is), and others have reported that in dried cotton fibers approximately 95% of the cellulose is in the crystalline state; Assaf, Haas, and Purves ( g ) , using another technique, found as much :is 27y0 amorphous cellulose in swollen samples of cotton linters. The crystalline cellulose may be deposited as such in the living boll, or crystallization may take place when the fibers undergo initial dehydration. Considering that convolutions appear when the fibers are dried for the first time, it seems probable that at least part of the cellulose is cryst’allized during thc period of initial dehydration. The work reported in this paper was undertaken to determine what changes occur during dehydration in terms of the molecular and micellar structure and how thest? changes affect the physical properties of the fiber.
X-ray patterns of undried cotton fibers taken from developing bolls showed little or no evidence of crystalline cellulose. The pattern of natipe cellulose appeared at the time the fibers underwent their initial dehydration. Undried cotton fibers possessed considerable plasticity. When they- were stretched, the slope of the cellulose spiral in the secondary wall was increased and fiber strength u-as increased. Some crystallization of the cellulose took place as a result of tension eten though the fibers had never been dried. Some crystallization of the cellulose occurred when undried fibers were transferred to nonpolar solvents. Attempts were made to prevent crystallization of cellulose upon drying by impregnating undried fibers with strong glucose solutions. Fibers impregnated with glucose and dried without tension showed diffraction lines from both substances oriented with respect Lo the long axis of the fiber. When the impregnated fibers w e r e stretched, certain other lines in the x-ray-pattern appeared in addition to the diffraction lines of the glucose and cellulose. Flax fibers, unlike cotton, showed some crystallization before dehydration.
hlATF$RIALS AND METHODS
Materials used in this study consisted principally of cottoll fibers from common American upland sbrains and from Pima, and American Egyptian variety. A small amount of work was also done on flax. The cott’on fibers were taken from developing bolls, ranging in age from about 23 days after flowering (4 to 8 days after secondary thickening was initiated) until the bolls cracked in the process of opening. The fibers were either used immediately without treatment or preserved in approximately 70% ethyl alcohol and st’ored until used. Small groups of th
