Earl E. Berkley

Degree of Polymerization of Cellulose in Cotton Fibers

* Division of Cotton and Other Fiber Crops and Diseases, Bureau of Plant Industry, Soils and Agricultural Engineering, Agricultural Research Administration, U. S. Department of Agriculture, Beltsville, Md. † National Cotton Council of America, Washington, D. C. THE PHYSICAL PROPERTIES of cotton are dependent on the fiber structure and shape. Their use value is also influenced by the appearance of the fibers and the products made from them. Fiber

Cotton—A Versatile Textile Fiber:

Certain recent researches on cotton are reviewed, together with further data on natural variations of it as found on the cottonseed and modifications of the fiber by chemical and physical treatments. No attempt has been made to present a general review. A more extensive over-all treatment of cotton quality may be found in a report by the Bureau of Plant Industry [11]. Cotton fibers grow first in length, then in thickness. The physical properties of the fiber and, therefore, its use value are determined by its length, fineness, and cell-wall construc tion, all of which are genetically controlled but are also sub ject to modifications by weather conditions during growth. Since fiber length is established before the cell walls thicken, length and cell-wall structure may be influenced independ ently. As growth proceeds there is a general trend toward compensation of loss of fiber length by added strength and vice versa; however, the failure of weather conditions to remain the same throughout the growing period of the fiber may result, for example, in short, weak fiber or long, strong fiber. Cotton fibers may be modified by swelling treatments while tension is applied. Such treatments may increase the fiber strength at the expense of other properties. The spinning quality of cotton is dependent upon a com bination of fiber properties and upon the spinning technique used. In general, however, the size of yarn or thread made from cotton is dependent upon its fiber length. For a given length, fiber fineness, and even strength, may influence the maximum count to be expected. Strong yarns require relatively strong fiber for any given fiber length and fineness. Uniformity of fiber length undoubtedly influences the ease of manufacture and the percentage of waste to be expected from a given cotton, but it is indicated that well-bred mod ern varieties have sufficient length uniformity to give good results. Within a variety, however, growth conditions, gin ning, and baling may affect the fiber-length uniformity enough to influence fiber property-yarn strength relationships. Since variety characteristics may be influenced by growth conditions, causing positive varietal relationships to reverse and become negative for environment, the analyses of data consisting of fiber properties and yarn strengths, except for very general treatments, will give more information if variety and environmental effects can be segregated. It is indicated that if good certified seed of suitable varie ties for each type of environment are planted, cotton of ac ceptable quality can be produced throughout the Cotton Belt. In selecting a cotton for specialized uses, variety and growth conditions as well as grade and staple should be considered for best results.

Fiber Fineness (Micronaire), Neps in Card Web, and Yarn Appearance Grades

ance grades and therefore limit the use of the cotton. Neps are small, tangled, ball-like masses of fiber. They result from the mechanical processing of the cotton. They may originate from machine picking, ginning, opening and cleaning, and particularly from the carding operation. Improper settings in any of these machines and excessive beating and over-heating of the cotton are known ( l, 2] to produce more than average neps. In addition to the neps caused by improper operation, certain cottons appear to be more susceptible

Some Possibilities and Limitations of X-Ray Methods for Measuring the Strength of Raw Cotton

TT~URING recent n~onths f)’e<(nent <)ues1io))s have come fotl)e(B)tton DlTHING C’t’(’111 1II01llh 1’1’1’</&dquo;(’111 qlll’H1iollH 11:1B’1’ (’1111)(’ i 1hl’ (iO/ OIl jj ’)’(’(’1J1lo1og’j(’;¡1 Lahol’:l1ol’Y J’I’g:ll’clillg 11,1’ ,.I:I&dquo;,....ifj,’:l1ioll of mnitou by X-ray methods. Amury tlm (I1H’s1ioIlS !I:IB’(’ bl’l’1I :-;twh :1&dquo;4 Can the X-ray method be used to classify cotton? Have you fomnl the 1-ray method satisfactory? How accurately does the ~’-r;ry method j>I<,,li<.< the spinning B’11111(’ of the cotton? How mud) does the «<jiiij>mi<>if <.1>,1 .> Ifrm~

The Effects of Fiber Fineness (Micronaire) on the Weaving Contraction in Selected Cotton Fabrics

in length and/or width is the result of the yarn axes being forced to describe a series of curves along the plane of the fabric due to the interlacing of the yarns, which takes place at the time of the beating-up and shedding motions during weaving. The amount of this contraction in weaving is influenced by yarn diameters, yarn density, yarn flexibility, warp and filling tensions, and fabric construction. Due to the differences in yarn structure, yarn preparation, and weaving tensions, the amount of contraction will not usually be the same for warp and filling, even in square constructions, i.e., when the warp and filling are of the same yarn number and there are the same number of ends and picks per square inch. It has been shown that many yarn characteristics are influenced by fiber fineness; therefore, it follows that weaving contraction would probably be influenced by fiber fineness. Although extensive work has been done on the geometric structure of fabrics and yarns [1 through 10], little data have been reported on this particular aspect of fabric structure. Peirce (8], in his excellent geometric analysis of fabric structure, suggested that differences in fiber &dquo;hair weight per centimeter&dquo; was a concomitant factor in yarn structure; however, the consideration of the effects of fiber fineness on yarn structure was beyond the scope of that particular study. Barella [1] and Schwarz (9] considered the importance of twist and fiber packing in yarn structure, and Hoffman [3] considered the bulkiness of yarns resulting from the use of fibers of mixed diameters. In none of the

Degree of Polymerization, Spiral Structure, and Strength of Cotton Fiber

Cotton fiber from bolls collected on opening and dried in the laboratory without exposure to direct sunlight were tested for the following fiber properties: fiber length, fineness, strength, spiral structure, and degree of polymerization (D.P.). When these individual properties were each correlated with the Pressley strength index in simple correlations, the spiral structure and Pressley strength index gave the highest r values, and the degree of polymerization and Pressley index the second highest. For variety effects, the D.P. and Pressley index gave a higher coefficient of correlation than the spiral structure and Pressley index. Significant r values were obtained between fineness and Pressley index for total and variety effects, between fineness and D.P. for all effects, and between spiral structure and D.P. for all effects. Further more, a significant r value was found when fiber length was correlated with chain length (D.P.) for total over-all effects. It is concluded that the length of the cellulose molecule (D.P.) is an important factor in the physical properties of cotton fibers. All multiple correlations, including the fiber properties used in the simple correlations, were highly significant for varieties within locations and for over-all effects. Spiral structure and chain length (D.P.) when correlated with Pressley strength gave the highest coefficient of correlation.

Effects of Blending Cottons by Fineness on Cotton Costs, Processing Efficiency, and Yarn Quality

a major factor in merchandising cotton [ 1 ] . Every sample of cotton contains some thin-walled fibers, and all fully matured commercial cottons contain both thinand thick-walled fibers.Fine cottons can be blended, therefore, with coarser cottons to gain a price advantage and, under certain conditions, to obtain greater yarn strengths for low cost fabrics. It is necessary.when blending fine and coarse cottons to use a level of fiber fineness which will result in the desired yarn ’under conditions of manufacturing. Since the number of neps increases as the Nlicronaire readings decrease, particularly in the range below 3.0 [121, certain cottons are limited to~industrial fabrics, toweling, drapes, and non-apparel uses. A given number of turns of twist per unit length of yarn made from fine fibers is more effective than the same amount of twist in yarns made from coarse fibers {6[. Fiber fineness is also Important in weaving. Yarns made from fine cottons have a larger diameter for a given yarn number than similar yarns made from coarse cottons, and there is a greater weaving contraction when using yarns of larger di-

Improved Instrument to Measure the Moisture Content of Lint Cotton, Seed Cotton, and Cottonseed

The cotton and cottonseed industries are modernizing technical methods and instru ments along with suppliers of other raw materials. Described herein is an improved electrical conductivity instrument for measuring rapidly and accurately the moisture content of lint cotton, seed cotton, and cottonseed. Moisture contents in percentages, based on total weights of samples, are indicated on a direct reading dial. Accurate measurements of ± 1% in the 3.3-22% moisture range are obtainable with this instru ment when compared with standard oven metheds. A relatively large representative sample (35 g. lint cotton, 100 g. seed cotton and cottonseed), control of sample density (600 lb./sq. in. pressure), and a stable electrical system are the contributing factors for a successful instrument.

Effect of Long Storage on Cotton

States during the past three crop years (Tibte 1 ) . The Nficronaire reading was higher than the average of recent growths, as was the upper half mean length: The yarns spun from the ACCO bale were stronger, the nep count was lower, and the yarn appearance grades were superior to the average of the cottons ginned in the past three crop years. These data demonstrate that there is no appreciable deterioration of raw cotton, as long as it is undamaged when stored and the storage conditions

Certain Variations in the Structure of Wood Fibers

but also within a given species or variety and even within a given plant. Natural cellulose fibers of commerce, such as cotton, flax, abaca, and wood pulp, are composed of plant cells. The physical properties of fibers are dependent upon their cellwall structure and the way in which they are woven together to form fabrics. Much can be learned by comparing the properties of the different fibers which tend to compete with each other. An attempt was made in this study to ascertain the structure in the different regions of the fiber. Wood cells were used so that each cell could be held in position throughout the study. Additional studies are needed on cotton and other single-cell fibers, using microtechniques. Preston [1] made certain observations on the nature of the spiral structure of the cellulose in plant tissue, stating that there was but one spiral which varied from one part of the cell to another. Bailey and Berkley [2] observed that there were two or