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The proximate chemical composition of total dust samples from five Texas cottonseed oil mills was determined. Dust compositions were highly variable and were affected more by the processing step than by differences among mills. Composition of cleaning room dusts reflected differences in soil minerals. Typical inorganic values were: silicon (12%), aluminum (0.5%), and iron (0.7%). Delintering dust was highest in cellulosic materials (40%), whereas the 23% protein composition of the hulling dust showed the influence of kernel fragments. Baling, dust contained large amounts of cellulose (38%) and noncellulosic organic constituents (36%).

Byssinosis, a respiratory disease, is caused by dust in cotton textile mills. The heterogeneous, complex dust varies in composition and activity in different "cotton-related" processing operations. Information concerning the constitution of "cotton dust" is reviewed. Relevance of a single dust standard for all cotton operations is discussed.

Inorganic and proximate compositions were determined for total and fine (under 20 μm diameter) dusts from cotton gins, textile mills; oil mills, and cotton compresses. The ash content of fine dusts was higher than that in total dust samples but decreased with the stage of processing in textile mills and gins. Inorganic composition often differed exten sively and appeared to depend on the soil composition and growing location. Large differences in water solubility and protein content also were observed. The difference between total and fine cardroom dusts was primarily in fiber content. Numerically and gravimetrically, the vast majority of mineral particles and plant fragments in carding dust appeared to be under 20 μm diameter. Little difference was found in the relative ratios of inorganic elements and nonfiber plant fragments in total and fine gin dust samples. Differences in dust composition Were often greater from one gin, mill, or compress to another than those among samples obtained at different stages of processing within the same plant

The feasibility of identifying, by microscopial and X-ray techniques, the biological source of cotton plant dusts produced from individual plant parts was determined. Major elements observed were magnesium, aluminum, silicon, sulfur, chlorine, potassium, and calcium. Some plant parts were distinguished by variations in elemental content. The most characteristic elements were potassium and calcium. Relative peak heights of elemental spectra were used to identify the plant part from which the dust was derived.

The effects of crystalline modification of cellulose and of water on the ESR spectra generated by the trapped free radicals in gamma-irradiated celluloses were investigated for cotton cellulose I, II, III, and IV, partially decrystallized cotton cellulose, ballmilled cotton cellulose, hydrocelluloses of cellulose III and IV, and ramie. On irradiation of the celluloses, free radicals were formed on the cellulose molecule, probably following dehydrogenation or chain cleavage. The free radicals located within the less ordered or amorphous regions of the cellulose reacted readily with water and were terminated. The radicals located within the more ordered regions of the celluloses could be made accessible to reaction with water by the interaction of the celluloses with solvents which caused dimensional changes in the cellulosic structure. In the highly ordered regions of the celluloses, even after long periods of time in solvents which caused large dimensional changes in the cellulosic structure, the trapped free radicals were not terminated by reaction with solvent or water. The ESR spectra of the irradiated, dried celluloses were determined at −160°C, the single-line spectra recorded had line widths of about 18-24 gauss. On the absorption of water by the irradiated celluloses, the ESR spectra changed and were dependent on the crystalline structure of the irradiated celluloses. The effects of different arrangements of the irradiated celluloses, as shown by their trapped radical spectra, particularly after interaction with water, were discussed.

The primary wall of fully matured cotton fibers has been isolated and its morphology and composition studied by electron microscopic examination and by chemical analyses. The pri mary wall appears to contain about 50% cellulose; protein, wax, and pectic substances occur in lesser amounts; cutin or suberin and mineral matter are also present. The concentration of noncellulosic substances in the primary wall is much greater than in the whole fiber.Electron microscopic examination of the primary wall indicates that it consists of a network of cellulose fibrils, having diameters of 100-400 Å, surrounded by the noncellulosic constituents. The oriented fibrillar systems observed with the polarizing microscope have not been seen in the electron micrographs of the specimens studied. There is an apparent increase in the diameter of the fibrils of the primary wall and in the denseness of the network as the fiber matures. The existence of layers in the cellulose network has been observed.

Photomicrographs of chemically modified cotton fibers, illustrating the alterations in the fine structure that were caused by the treatments, are shown. An attempt is made to correlate structural changes in the fiber with changes in such fiber and fabric properties as breaking strength, elongation, and dry and wet wrinkle recovery.

Diffraction patterns from single fibers have shown sufficient resolution in the 002 density peaks expected from near perfect spiral structures that direct measurements may be made independently of any theory. Single walls from fractured weakened fibers are observed between crossed polarizers and give an easy measure of fibril orientation. Both sets of measurements are used to corroborate the results obtained from a theoretical analysis of the 002 diffraction arcs recorded for bundle samples.

Experiments designed to complement microscopical studies and to attempt a practical evaluation of the effectiveness of various agents which impart resistance to dry soil are reported. Various methods of applying soil to fabric were evaluated, as was the ef fectiveness of a number of soil retardants. Soils included carbon blacks of a range of particle sizes, a natural clay, and a synthetic soil whose formula approximated the com position of natural soil, containing fatty materials. Fabrics were also soiled by foot traffic on the floor. Results were interpreted from reflectance data and from radioactive tracer assays of weight of soil takeup. In attempting to elucidate the mechanism of dry soiling. the effects of textile construction, electrical charge on the fiber, particle size of soil as related to topography of fiber surface, surface hardness, reducing surface rough ness. and lowering surface energy were considered. It was shown that soil takeup is directly related to specific surface. It was found that grey cotton is slightly more re sistant to soil than bleached cotton, and that increased smoothness of fiber. even to com plete obliteration of native rugosities, did not necessarily impart soil resistance to cotton fabrics. The most successful types of antisoiling agents for dry soils appear to be col loidal particulate applications such as silica or alumina, and additive finishes which lower surface energy of the tiber. Only a few of the typical commercially available soil re tardants were used in these studies. The project was a short term one and the experi ments were designed for the study of the mechanism of soiling of cotton textiles which would be subject to in-place cleauing. Many new soil retardants were marketed after the experiments had been initiated.

Cotton fiber was treated with aqueous trimethylbenzylammonium hydroxide (Triton B) at concentrations over the range 25%–40%. After complete removal of the swelling agent, the samples were evaluated for the extent of swelling, strength and elongation, birefringence, moisture regain, density, crystallinity, x-ray diffraction patterns, and microfibrillar morphology. Electron-microscopical examination and other evaluation of fine structure properties revealed that the nature of swelling is intercrystalline up to 30% concentration of Triton B, and intracrystalline beyond that. Although the swelling as measured by propanol-2 retention after treatment with 30% Triton B is about twice as much as that of the control, the original structure remains almost unchanged except for some gain in strength and elongation and increase in moisture regain. At 32% Triton B concentration and beyond, rapid decrystallization takes place, accompanied by a fall in birefringence, density, and crystallinity index. X-Ray analysis showed significant loss of lateral order and partial conversion of cellulose I to cellulose II at 35% and 40% Triton B concentrations. The results indicate that, used at the critical concentration of 30%, Triton B can be a useful swelling agent for cotton fibers as it opens up the fine structure of cellulose considerably without impairing any important physical properties.

Electron microscopical studies of changes in cotton fiber microstructure, after ex posure of the fibers to the cellulase in filtrates prepared from cultures of Myrothecium verrucaria, showed evidence of the transverse, jagged cuts into the cellulose structure previously seen by cytical microscopy. The degradation appeared localized in areas along the length of the fiber which were not related to any recognized component of fiber structure. Micrographs of fragmented, degraded fibers showed etching of the macro- fibrils of the sheets of secondary wall and a sharpening of the image of the individual microfibrils. Continued enzyme attack produced smaller fragments and hydrocellulose- like particles. Measurements of changes in tensile strength, swelling in alkali, and in glucose yield were correlated with changes in microstructure. The extent of fiber degradation by cellulolytic culture filtrates was limited and could be continued only if fibers were swollen between filtrate exposures. No evidence of damage to the cellulose structure was seen which could not be explained hy hydrolysis at the β-1,4-glucosidic linkage.

The currently-used types of cross-linking agents and some of their effects on cotton are discussed. The primary weaknesses or shortcomings of the finishes achieved with these agents are pointed out. It can be concluded either that the ideal cross-linking agent for cotton has not been found or that the best technique of application has not yet been discovered. However, considerable success is being had in producing minimum- care fabrics by the use of many cross-linking agents, especially the N-methylol type. Although cross links through primary covalent bonds are largely responsible for the observed physical changes in cross-linked cotton fiber, secondary valence cross links also may produce significant changes, some of which appear to be rather durable. Evidence is presented which indicates that polymer formation produced concurrently with cross-linking improves the over-all minimum-care properties of cotton fabric, although polymer formation alone does not improve the wrinkle recovery. Cross-linking agents which are capable of forming thermosetting resins generally are required in somewhat larger add-ons to produce wrinkle recovery angles in the practical range than are those agents that do not form thermosetting resins. The extent of permanent set is related to the extent of cross-linking. Moisture regain and density of the cross-linked cottons are more dependent upon the state of fiber swotting at the time of cross-linking than upon the extent of cross-linking.

Characteristic wide-line proton magnetic resonance absorption spectra of a number of representative cellulose preparations have been obtained in the dry state and after addition of about 7% water. Line widths, second moments, spin-spin and spin-lattice relaxation times have been determined. The second moment of the absorption curve of dry cellulose was found to correlate well with the crystalline fraction for most specimens. A technique is described for determining the number of water-cellulose protons exchanging relative to the number of cellulose protons not exchanging. The reduction in absorption line width observed when water is added to cellulose is shown to be quantitatively consistent with such a proton exchange phenomenon.

The topography of unmoditied cotton fibers has been examined microscopically by means of surface replica techniques. The outstanding characteristic of the surface is a system of roughly parallel ridges and grooves spiraling around the fiber at an acute angle (usually 20 30 ) to its axis. The pattern of the surface is a reflection of the spiral fibrillar structure of the cellulose beneath the primary wall of the fiber. The average height and distance between ridges is approximately 0.5 micron. and many of the ridges are 10 or more microns in length. The surfaces of most native cottons are quite similar, although statistically significant differences in the average distance between ridges were found between certain samples The surface of fibers from unopened bolls is relatively smooth, but assumes the roughness of the typical fiber on drying for the first time. A characteristic surface formation ap peared to be associated with fibers known to have undergone compression. Drastic abrasion largely obliterates the normal appearance of the fiber surface.

Microscopical studies of surface replicas of chemically finished or modified cotton fibers have shown that the characteristic surface of native cotton is often altered by various commercial and experimental treatments. While removal of the wax from the fiber sur face has little effect, scouring usually uncovers the fine cellulose fibrils of the primary or even secondary walls. Mercerization does not eliminate the rugosities of the native fiber surface. Additive finishes, including starch, carboxymethyl cellulose, colloidal silica, and acrylic polymer resins change the original fiber topography to an extent dependent on the amount applied. In general, particulate additives tend to concentrate in the grooves of the fiber surface when applied in dilute formulations, but cover most of the fiber surface at higher concentrations. Chemical modifications which increase the fiber cross sectional area make the fiber surface smoother, hut extensive swelling of the cellulose derivative during its preparation appears to create roughness in some modifications. Crease resistant finishes do not alter the fiber topography significantly.

IR spectra in the 7.5–25.0 μ region are shown to be unique for the individual long chain odd carbon numbered saturated fatty acids and for the monounsaturated even carbon numbered fatty acids, their isomers, and polymorphic modifications. IR spectra are presented which illustrate similarites and dissimilarities resulting from chain length differences and polymorphic variations for monounsaturated acids. X-ray crystal long spacings for the saturated odd carbon numbered acids are compared with literature values. X-ray crystal long spacings for monounsaturatedtrans acids are shown to be related to carbon chain length and independent of the location of unsaturation. Diffractograms and IR spectra of the 2 polymorphic modifications of elaidic acids are presented. IR spectra illustrating band differences forcis andtrans isomers are shown.

The modification of cotton cellulose by environmental conditions or by chemical treat ments for specific end uses ordinarily occurs at submicroscopic levels. Observations with the electron microscope have proven to be useful in delineating regions of the fiber cellulose affected by a variety of treatments, including dyeing, mercerization, acid and enzymatic hydrolysis, derivative formation, and resin impregnation. The appearance of fiber fragments treated in these ways or derived from treated fibers is illustrated and discussed.

Effects of acetylation on the morphology and submicroscopic structu e of cotton have been studied by light and electron microscopy. The cross-sectional area of partially acetylated (PA) fibers increases with degree of substitution. The average refractive index of PA cotton decreases with increase in acetyl content, as do the indices measured parallel and perpendicular to the fiber axis. Refractive index measurement appears to be a feasible method for estimating the chemical composition of PA cotton. At early stages of esterification, unevenness of reaction along the length of fibers may be demon strated by dyeing and swelling techniques. Acetylation causes the surface of cotton to become smoother, and obliterates the micro- fibrillate pattern characteristic of scoured fibers. PA cotton fibers swell when embedded in methacrylic esters by polymerization. The swelling causes separation of the lamellae of the secondary wall, and permits electron microscopical observations on the interior elements of the fiber to be made on thin cross sections of the specimen. Fragments of PA cotton obtained by wet- beating show progressive loss of the fibrillate character of unacetylated cellulose as the acetyl content increases. At high degrees of substitution, the PA cotton fragments resemble the spongy particles obtained from wet- beaten acetate rayon and Arnel. The results of microscopical examination are considered in terms of fiber structure.

The ir absorption spectra of Valonia ventricosa cellulose, hydrocellulose i, and hydrocellulose ii at ambient and liquid nitrogen temperatures have been compared. Some of the bands exhibit a striking increase in peak intensity at the lower temperature. On cooling, changes to lower frequencies occur in the OH stretching region and to higher frequencies in the 1800–300 cir−1 region. The changes which were observed on cooling are undoubtedly associated with hydrogen bonding effects since the positions of absorption bands in the spectra, obtained under the same conditions, of analogous specimens containing no hydroxyl groups are not affected by temperature.

A technique for obtaining differential infrared absorption spectra of chemically modified cottons is described, and its value illustrated by selected examples. With KBr discs in a double-beam spectrophotometer, absorption bands common to unmodified and modified cottons can be reduced in intensity by placing equivalent quantities of cellulose in both beams The resulting spectrum facilitates identification of the molecular species introduced in making the derivative. The method is useful in obtaining spectra of the reaction products of cotton and intermolecular crosslinking agents at low degrees of addon Application of the method to cotton reacted with compounds of the dimethylol urea type and with other agents is described.

Native and chemically treated cotton fibers abraded hy laboratory instruments and other means were examined by light and electron microscopy. Characteristic patterns of abrasion damage for a variety of experimental conditions have been estahtished. and reasons are suggested for the abrasion response of the fibers. Marked differences were noted in the abrasion behavior of most cottons when tested in the dry and wet states, but these differences are minimized by resin treatments that cross-link the cellulose.

Cotton fibers are constructed principally of macromolecules of cellulose. These are disposed in the fiber in such a way as to display a number of aspects, which collectively may be referred to as the "supermolecular structure." It includes such features as molecular chain length, polymolecularity, natural cross-linkage, crystallinity, crystal modification, crystallite size, orientation. accessibility, and chemical modification. Super imposed on these structural aspects is the gross morphology of the fiber itself. Many of these aspects have an influence in one way or another upon the response which the fiber makes when subjected to a variety of mechanical forces, which collectively may be referred to as "mechanical behavior." Among the responses considered are strength, elongation, stiffness, toughness, elasticity, and resilience. Selected examples are pre sented, showing how the mechanical behavior is conditioned in various ways by the supermolecular structure.

On acid hydrolysis of cotton, the degree of polymerization (DP) of the insoluble residue falls rapidly to a low level (leveling off DP). Continued hydrolysis results in further losses in weight, but the DP, and the micelle dimensions, remain unchanged. Immergut and Rånby [6] suggest that individual micelles at the leveling off DP disap pear in entirety; i.e., further action of acid yields soluble fragments only. The present investigation was undertaken to compare the action of enzymes on the micelles with that of acids. The study was broadened by the inclusion of hydrocelluloses from cottons treated in various ways, and further extended to include the parent materials from which the hydrocelluloses were prepared.

X-ray fluorescence has been applied to the analysis of a wide variety of chemically treated cotton textiles. Sample-preparation techniques suitable for the determination of elements heavier than Na have been developed, and the effect of fabric structure on counting rate has been investigated. Selected examples of results obtained in the analysis of some 20 elements applied to cotton fabrics are given. The problem of particle size when the element is in the form of pigment is discussed.

Changes in the structure of cotton fibers after expesure to gamma, high-energy electron, and thermal neutron radiations, in various ambient atmospheres, were evaluated by the techniques of optical and electron microscopy. Radiation exposures evaluated were: gamma rays, 105 to 4 × 108 r.; 2-Mev electrons, 5 × 104 to 108 rep; integrated thermal neutron fluxes, 5 × 1014 to 1017 nvt. Changes in the physical and chemical properties of similarly irradiated fibers have been, or are to be, reported in other pub lications. All irradiated, unmodified cottons could be differentiated from unexposed cottons by optical microscopical observations of samples stained in Nile Blue Sulfate. Gamma ray and electron exposed samples differed from unexposed fibers. in swelling behavior in 0.2 M ( in Cu) cupriethylenediamine hydroxide, but thermal-neutron-irradiated cotton differed from the control only after exposure to an integrated flux of 1017 nvt. Electron micrographs of the fibrillation patterns exhibited by fibers exposed to gamma and electron radiation doses of 5 X 106 to 108 r. or rep on beating in water in a Waring Blender showed the formation of increasingly smaller fragments of samples. Some shortening of fibrils and an increase in number of broken ends of microfibrils were seen in neutron-irradiated cotton exposed to 10" nvt; at lower integrated neutron fluxes, fibrillation was unchanged. No distinct differences were found in microscopical tests between gamma and electron irradiated fibers or between gamma-exposed fibers irradiated in oxygen and nitrogen. At doses of 4 × 10" r. of gamma rays, the trend toward smaller fragments reversed and short chunks of material were observed. Varying amounts of degradation were observed in modified cottons after irradiation. Smaller fragments were observed in cottons modified to change and reduce the total crystalline cellulose; the fibrillation of acrylonitrile-treated cotton appeared unchanged, but irradiation produced a decrease in the size of fragments of dichloropropanol- and dimethylol cyclic ethyleneurea-modified samples.

The appearance, growth, and structure of a cotton fiber are described, and photomicrographs and electron micrographs are used to illustrate both gross and fine features of the cell wall morphology. Heretofore, microscopy of the fiber has been limited to the use of dispersion, swelling and staining methods, in plain and polarized light. The development during the present study of methods for isolation of individual components of the cell wall for purposes of electron microscopy has permitted interesting observations with the light microscope. Quantitative measurements of shrinkage in the isolated primary wall of the cotton fiber during mercerization confirm its restrictive influence on the fiber during swelling in various agents. Electron microscope studies have been made on isolated primary wall fragments which have been purified by removal of noncellulosic constituents by extraction. These have revealed that the cellulosic portion of the membrane is a network of fibrils interlaced in a sort of fabric in which the general system of orientation is axial on the outer surface and transverse on the inner surface. The cellulose framework is impregnated with a complex of waxes, pectinaceous, and proteinaceous substances. The first layer of secondary thickening, called the "winding layer," has been isolated from 17-day old cotton fibers and photographed with both optical and electron microscopes. It is revealed to be a continuous sheet or layer made up of alternating bands of fibril bundles which spiral about the fiber at an angle. The wider bands have a closely packed parallel arrangement of fibrils while the narrower bands which connect them consist of two systems of fibrils at right angles to one another in an open-weave pattern. Electron micrographs of fragments of the main body of the secondary wall show an entirely different pattern of fibril arrangement from either the primary wall or the winding layer.

The location of soiling agents such as colloidal and activated carbon, floor soil. a syn thetic soil, and a clay on gray and modified plain weave cotton fabrics soiled under con trolled conditions was determined by light and electron microscopical examination. Cross and fine geometry of fabric and fiber play a major role in determining the dis tribution of soil in most cases. The mechanical entrapment of soil particles and ag glomerates between fibers near the surface of the fabric is repeated in the accumulation of soil in the natural or induced irregularities of the native and modified fiber surface. The presence of soft films on the fiber surface extends the quantity of soil and its dis tribution. Sorption of the soil particles on apparently smooth areas of the fiber also occurs to a significant extent.

The application of X-ray fluorescence to the qualitative and quantitative analysis of chemically modified cotton textile materials is described. The scope and flexibility of the technique have permitted the determination of more than 20 elements with, greatly reduced elapsed time compared with the corresponding spectroscopic or wet methods. Precautions to be observed in preparing standards are discussed. Results of the analysis of typical modifications and their significance in the development of cottons for specific uses are described.

Changes in the cross-sectional area and circularity of cotton fibers tensioned in water and other media have been measured microscopically. It was found that the area increased significantly over that brought about by water-swelling alone. Fibers tensioned in bundle form at 0.45 g./grex for 1 hr. in water showed an average increase of 98% in area compared to dry untensioned fibers, and an increase in circularity (axis ratio) of 57%. These increases were not retained on drying, even when tension on the fibers was maintained. Immersion without tension in urea solution, ethylamine, or sodium hydroxide of mercerizing strength, followed by removal of the reagent and drying, in each case produced increases in area and circularity over those of the untreated fibers. Tensioning at 0.45 g./grex during im mersion in these reagents increased the circularity, but decreased the area with respect to the untensioned fibers. The elongation of fiber bundles tensioned in the various media was measured. The sodium hydroxide solution produced the greatest elongation.

The application of x-ray emission techniques to the qualitative and quantitative elemental analysis of chemically and additively modified cotton textiles has been investi gated. Sample preparation and calibration techniques which appear to be suitable for the analysis of textile materials have been devised. The method has been applied to a variety of samples containing some 20 individual elements. The technique is useful for identifying the elements present in fabrics finished with poorly defined agents. It has been applicable to problems involving the add-on and subsequent loss of fungicidal agents containing such elements as Cd, Zn, Se, Cl, S, and P. Typical results obtained with a number of modified cottons are given.

Cotton/polyester blends can be rapidly and accurately analyzed by x-ray diffraction techniques to give results well within the specification set by the Federal Trade Commission.

A technique is described by which the protons in water–cellulose sorption systems may be assigned to four categories. The protons are quantitatively divided into water- and cellulose-associated protons and these categories are further subdivided into interchanging and non-interchanging species. The relationships are derived on the assumption that the line narrowing observed in the NMR spectrum of celluloses on the addition of moisture is due to the rapid interchange of some of the water and cellulose protons (or their spins). The experiments were carried out at water–cellulose concentrations of about 7% on a variety of cellulose samples differing in supramolecular structure as characterized by crystalline fraction and lattice type. Data are presented which indicate that the larger the proportion of water protons involved in the interchange process, the larger the spin–spin relaxation time of those water protons not involved in the interchange. It is concluded that linewidth of the narrow component of the water–cellulose NMR signal is not related to sorption processes as simply as previously suggested.

Electrostatically precipitated respirable dusts from six major U.S. varieties and growing areas were analyzed. From 81-95% by weight, was under 15 micronm diameter. Composition was affected more by growing location than by variety. Dusts contained 16-28% ash, 8-9% moisture, and 62-76% organic matter, including 16-31% protein and 2-12% cellulose. Inorganic composition reflected soil type and minerals. Major elements were silicon, calcium, potassium, phosphorus, magnesium, and aluminum. Infrared spectra of dusts resembled proteins, but water extract spectra did not. Possible implications concerning byssinosis are discussed.

Chemical impregnations to achieve flameproofing, wrinkle resistance, or modification to increase dimensional stability are typical processes aimed at improving the properties of cotton. These treatments involve the possibility of chemical linking of the cellulose to the impregnating reagent, or the formation of cross linking bonds between the cellulose members themselves within the fine structure of the fiber. Insolubility of the entire fiber or of small pieces of fiber in a dispersing agent such as cuprammonium hydroxide or cuprietheylenediamine hydroxide (CED) has been accepted as a characteristic of cross-linked cellulose. However, it has been difficult to evaluate the extent of cross linking; and the location of chemically modified areas within the fiber has been a matter of speculation. A new technique for treating thin sections directly on the specimen screen permits visual study of these phenomena.

It is most appropriate that the first session of an International Conference on Electron Microscopy, devoted exclusively to technological fibres, should be held here at Berlin where the pioneering work of this kind was conducted over twenty years ago (1). Moreover, a gathering of many workers from the field of applied research provides a useful opportunity to assess the extent of the general progress.