Jacques J. Hebert

Cross-Sectional Parameters of Cotton Fibers

A rapid, accurate method of evaluating cross-sectional parameters of cotton fibers was developed. The effects of swotting cotton while slack or under tension with various agents were ascertained from the resulting data.

Is the Spiral Angle of Cotton Constant

Optical studies of cellulosic fibers confirm the high alignment of cellulose chains in fibrils. However, in the cotton fiber the fibrils are not parallel to the fiber axis, but spiral around the axis as a, coiled helix [1]. In addition, the fiber itself has a convoluted structure. It has been pointed out by Meredith that the spiral angle of undried cotton may be a constant, irrespective of genetic variety [6]. He found that the spiral angle,

A New Single Fiber Tensile Tester1

A new instrument for single fiber tensile testing is evaluated and data from two cotton species are presented. The instrument allows rapid accumulation of data that, before inception, were extremely tedious and labor intensive to obtain. Results include tensile strength and percent elongation at different gauge lengths and rates of extension, and an optical measure of fiber diameter or ribbon width as well as an indication of the extent of convolutions.

Strength of the Primary Wall of Cotton Fibers

At a recent meeting’ on the structure and performance of cotton fibers, the subject of primary wall strength came up time and again. It became obvious during these discussions that, to date, little is known about the strength of the primary wall relative to the secondary wall or main component of fiber architecture. For this reason we looked into our study of strength as a function of fiber development and determined that we in fact had data related to this issue. Our reasoning was as follows: The cotton fiber originates as the elongation of a single cell in the epidermis of a seed coat. It grows in two stages. The first few weeks post-anthesis, the fiber elongates to a genetically prc-determined length. During this period it consists of a cuticle (proteinase material, pectins, and waxes) and a primary wall of cellulose fibrils surrounding the living cytoplasm within the central canal or lumen. These fibrils form a basketweave-like network. During the next stage (about two weeks post-anthesis), the secondary wall begins to thicken. The cellulosic fibrils are laid down from the outside wall inward in a spiral or helical array until the boll opens. By studying the sequential synthesis and arrangement of the fibrils making up the architecture in the young fibers, and following this procedure during the development stages of fiber growth, we were able to isolate fibers that contained only primary wall material. Flow-

Role of silicon in developing cotton fibers

Abstract The concentration of silicon is high during the elongation phase (approximately day 1 through day 21 post‐anthesis) of cotton fiber development. The ratio of the amount of silicon per mass of fiber peaks at the time when secondary wall initiation occurs. This suggests that silicon has one or more functions during a specific phase of cotton fiber development.

Seed Coat Fragments in Cotton Yarns

Five Acala cottons, two with high and three with low seed coat fragment counts, were included in a study of fiber properties to determine plausible causes of the pro pensity for certain cultivars to produce a high seed coat fragment count. Physical properties were determined and compared for each variety grown in three locations.

A Method of Automating the West Point Cohesion Tester

tester. (~entry [2] has dl’scribed a semiautomatic method to obtain the average drafting force of the W est Point cohesion tester by means of a fading memory integrator. This letter describes a method by which the area under the force-time curve of the W est E’oint cohesion tester is obtained automatically with a continuous integrator. The instrument used in conjunction with the West Point cohesion tester was an Instron ’ I tensile tester, floor model Tut -8, with a Type-1 basic chart drive and Instron integrator. Figure 1 shows a hlock diagram of

Effect of Convolution Angle upon Cotton Fiber Strength

zero degrees. Fiber bundles from this sample yielded a zero gage length tenacity of 53.0 g/tex. This experimental sample had a 50% x-ray angle of 21°, which agrees with the value reported for the constant spiral angle of unconvoluted fibers [2, 5]. The relationship of experimental fiber bundle tenacity to corrected convolution angle is shown in Figure 1. Convolution angles were corrected for edge curling according to the method of Meredith ~5J. The linear correlation coefficient for Figure 1, -0.92, is significant at the 99% level. This is to be expected, since the strength of fibers is associated with x-ray orientation angle, and previous work [4] pointed out the dependence of x-ray angle upon convolution angle. These results agree with those of Duckett and Cheng [2]. Statistical analysis showed that the linear correlation between the calculated and experimental values of tenacity was highly significant (r = 0.93).

Tension and Resin-Treatment Effects on Properties of Scoured and Mercerized Cotton Fibers and Fabrics of Different Constructions

Fabrics of printcloth weight in plain and basket weave were crosslinked with dimethylolethyleneurea to 2, 5, and 10% add-on. Specimens were dried slack or under tension before curing. The amount of crosslinking, controlled by resin pickup, produced reasonably consistent nitrogen contents in samples when other parameters were varied. Among the properties measured were fiber density, fabric thickness and area changes, fabric tensile and wrinkle recoveries, and single- fiber tenacity and tensile recovery. Relationships of properties to nitrogen contents and among various physical proper ties were frequently influenced by tension, fabric construction, and pretreatment.

Reversal frequencies in developing cotton fibers

Directional reversals in the helical deposition of fibrils affect the performance of cotton fibers. A developmental study was therefore conducted to determine the in fluences of genetics and developmental pattern on the incidence of these reversals. One cultivar of cotton, Deltapine 61, was studied in both 1980 and 1981; four other cultivars, Acala SJ-5, Stoneville 825, Stoneville 213, and Pima S-5, were studied only in 1981. Of these, the first four are upland cotton (Gossypium hirsutum L.) while the latter is a long-staple cotton (G. barbadense L.). Reversal frequencies were measured by polarized light microscopic techniques. In each cultivar, reversals were first detected after the third week of fiber development, coincident with the initiation of secondary wall formation. Reversal frequency increased with fiber maturity. Because reversal frequencies increased with fiber age, it seems that not all layers of the secondary wall reverse together. Slippage between layers may result from reversals occurring during late stages of fiber development. A plausible explanation for the two types of reversals reported in the literature is offered.