Crystalline structure of developing cotton fibers

Cellulose, 2005

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using sideloaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose Ib followed by integration of the crystalline and amorphous (background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional crystallinity determinations using the Segal or the Ruland -Vonk methods. The determined cellulose crystallinities were 90 -100 g/100 g cellulose in plant-based fibres and 60 -70 g/100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production.

Textile Research Journal, 2001

Cotton fibers develop a significant crystalline structure during the first week of secondary wall synthesis. Marked increases in the degree of crystallinity, crystallite dimensions, and breaking forces occur between 20 and 30 days post-anthesis (dpa). As the fiber cells mature and dehydrate, the cylindrical tubes collapse into convoluted ribbons. The dried fibers have lower breaking strength and higher breaking elongation. Wide-angle x-ray diffraction and solid-state NMR results show lowered average crystallite dimensions with little change in the overall crystallinity upon dehydration. In developing cotton fibers, dehydration appears to cause decrystallization, distortion of crystal surfaces, and increased disorder in the intercrystal and interfibril regions, driven by removal of water during cell collapse and by the formation of new intermolecular secondary bonding. This, in turn, builds up stress at the molecular level, lowering strength and increasing crimp and elongation in the...

Journal of Applied Polymer Science, 1999

In this article, data on cellulose crystallite orientation parameters measured in terms of the Hermans orientation factor, average angle of orientation (␣ m ), and 40, 50, and 75% X-ray angles in respect to the same 13 cotton cultivars grown at different agroclimatic locations and in different crop years in India are presented and discussed. It was observed that whereas the average values of the X-ray orientation parameters are different for different varieties they remain practically invariant within individual varieties with change of the location of growth. The orientation parameters, therefore, appear to be genetic in origin and independent of the agroclimatic conditions of growth. It is believed that these results can be suitably exploited by cotton breeders in evolving varieties with an increased strength of fibers.

Polymer Degradation and Stability, 2003

In this study, we investigated that how the crystalline structure of cellulose in cotton linters changed during soda, sulfate and organosolve pulping processes by using X-ray diffraction and FT-IR spectroscopy. It was defined that crystalline structure of cellulose in cotton linters was more effected in organosolve pulping than in soda and sulfate pulping. It was found that the degree of

PROBLEM As is known, natural cellulose of various origin is a semi-crystalline polysaccharide, which contains 50-80% of crystalline phase in a form of rod-like crystallites of different sizes. Knowledge of sizes of crystallites is very important because it allows clarify the supramolecular organization of cellulose fibers and structure of cellulosic products such as micro-and nanocrystalline particles, nanofibrils, etc. There are several methods for measuring the size of the crystallites: electron microscopy (EM), atomic force microscopy (AFM), wide-angle X-ray scattering (WAXS), etc. Besides the average length of crystallites can be estimated from level-off degree of polymerization (P) of the hydrolyzed cellulose samples. The results of EM, AFM, P and other methods showed that crystallites of natural cellulose have rod-like shape, 3-15 nm in transverse direction and 100-500 nm in longitudinal direction. However, the EM, AFM and P methods require prior isolation of the free crystallites, for example by acid hydrolysis. On the other hand, WAXS is considered as a non-destructive method that is widely used to estimate the sizes of crystallites by means of the Scherrer equation. This equation was proposed as early as the beginning of the 20th century, and it continues to be widely used at present, despite significant limitation, and namely: width of the X-ray diffraction peaks depends not only on the size of crystallites but also on other factors, such as instrumental effect and second-order distortions of crystalline lattice caused by paracrystallinity, dislocations, twinning, internal stresses, boundaries of crystallites, etc. This limitation of the Scherrer equation is often ignored, which leads to unreliable results. For example, study of pulp, bast fibers and cotton cellulose by approximate WAXS-Scherrer method gave low Scherrer's length of crystallites, 20-35 nm, instead of their actual length of 100-200 nm. This discrepancy may be due to neglect of such factors as lattice distortions, instrumental factor, incorrect orientation of the sample during recording, overlapping of reflection (004) by other reflexes, etc. When measuring the transverse sizes of cellulose crystallites, the difference between the results obtained by WAXS-Scherrer method and independent methods is smaller than in the case of determination the length of crystallites. The method of measuring the correction for the instrumental factor is well known. However, the methodology for determining the contribution of lattice distortions to the width of diffraction peaks is complex, and therefore it was used in a minor extent. The purpose of this research was elaboration of simple algorithm for determining the contribution of lattice distortions to broadening of diffraction peaks, which allows to find the actual sizes of crystallites by means of non-destructive WAXS method.

Cellulose, 2019

Cellulose is often described as a mixture of crystalline and amorphous material. A large part of the general understanding of the chemical, biochemical and physical properties of cellulosic materials is thought to depend on the consequences of the ratio of these components. For example, amorphous materials are said to be more reactive and have less tensile strength but comprehensive understanding and definitive analysis remain elusive. Ball milling has been used for decades to increase the ratio of amorphous material. The present work used 13 techniques to follow the changes in cotton fibers (nearly pure cellulose) after ball milling for 15, 45 and 120 min. X-ray diffraction results were analyzed with the Rietveld method; DNP (dynamic nuclear polarization) natural abundance 2D NMR studies in the next paper in this issue assisted with the interpretation of the 1D analyses in the present work. A conventional NMR model's paracrystalline and inaccessible crystallite surfaces were not needed in the model used for the DNP studies. Sum frequency generation (SFG) spectroscopy also showed profound changes as the cellulose was decrystallized. Optical microscopy and field emission-scanning electron microscopy results showed the changes in particle size; molecular weight and carbonyl group analyses by gel permeation Prepared for Cellulose 25th Anniversary Special Issue.

Textile Research Journal, 2000

Surface wetting measurements and several analytical techniques including FTIR/ATR, DSC, TGA, and pyrolysis-GC/MS are used to characterize the noncellulosic components of developing cotton fibers as intact components of the fiber structure. Water contact angle measurements are most sensitive to the presence of hydrophobic compounds on the surfaces of cotton fibers of all ages and to their removal by alkaline scouring. In general, FTIR/ATR, DSC, TGA, and pyrolysis-GC/MS provide clear evidence of specific noncellulosic components in developing cotton fibers through the onset of secondary celt wall synthesis. Waxy compounds are evident by their melting endotherms in DSC thermograms, carbonyl bands in FTIR spectra, and mass spectra in the untreated developing fibers between 12 and 17 dpa. Pectins are detected by. FTIR in the 14 dpa and mature fibers. FTIR/ATR measure ments indicate the presence of proteins in untreated fibers up to 16 dpa and water-rinsed fibers up to 18 dpa. The presenc...

Journal of Environmental Sciences. Mansoura University, 2020

Nowadays, cellulose nanocrystals (CNC) play a major role in industrial processes due to their unique properties which, in turns, able to enhance the physical properties of bulk materials. The interstice properties of CNC are vary regarding to the source of the used cellulosic materials. The study aimed to characterize cellulose CNC extracted from two different genotypes of cotton slivers; Egyptian extra-long staple (G.88) and upland medium staple length (BF FK37). As per acid hydrolysis, CNC was extracted from different genotypes of cotton slivers by the use of H2SO4 60% (w/w) at 60 ℃ for 60 min. Then, the extracted CNC was characterized by making used of different tools e.g., transmission electron microscopy (TEM), Dynamic Light Scattering (DLS), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Thermo Gravimetric analysis (TGA). Results revealed that, CNC was, successfully, extracted by acid hydrolysis of cotton slivers. Notably, the size of the obtained CNC was varied as genotypes of cotton slivers varies, which attained as shown from TEM; the average dimensions (diameter × length) of 36.46 ± 7 nm × 355 ± 98.3 nm for extra-long staple, 37.2 ± 14 nm × 284 ± 83 nm for medium staple. This fact was further supported by DLS as the size of extra-long staple was 22. 45 d.n and 35.77 d.n for medium staple. In addition, XRD results demonstrated that, both genotypes excited cellulose type I (crystalline polymorph). However, CNC extracted from extra-long showed higher crystallinity index (80%) than observed from medium staple. Moreover, the thermal stability observed for CNC of extralong is significantly higher than obtained from medium. By varying of the source of CNC, the size of the obtained crystals was varied besides crystallinity index and their thermal stability properties. Therefore, the using of extra-long staple length cotton slivers led to reduce the crystal size with improving in both crystallinity and thermal properties.

Materials, 2013

Cotton fibers are natural plant products, and their end-use qualities depend on their stages of development. In general, the quantity of cellulose in cotton fibers increases rapidly, thus it leads to compositional, structural and physical attribute variations among the fibers with shorter and longer growth periods. This article discusses recent progress in applying the Fourier transform infrared (FTIR) spectroscopic technique to characterize these differences, to discriminate immature fibers from mature fibers, to assess fiber maturity and crystallinity and also to unravel the band assignments in crystalline and amorphous celluloses. The results were achieved through the use of various strategies, including wet chemical analysis, principal component analysis (PCA), simple algorithm development, two-dimensional correlation analysis and other independent fiber tests. Of particular interest is that, in general, immature fibers might have the characteristics of less than 21-28 dpa, M IR < 0.58 (in the maturity range of 0 to 1.0) and CI IR < 42% (in the crystallinity range of 0 to 100%).