Cellulose fibers morphology

Fig. 5 Typical optical micrographs showing the effect of chemical reagents on cell morphology a control, b nalidixic acid (0.1 mM), c chloramphenicol (0.3 mM), d dithiothreitol (1.0 mM). Bold arrow bacterial cell, arrow cellulose fibers. Reprinted with permission from [37]...

An Interpretative review of the reactions initiated by macrocellulosic free radicals with vinyl monomers to yield block and graft copolymers of fibrous cellulose was made. Macrocellulosic radicals are usually formed by interactions with radiation or chemical redox systems. Important factors in these heterogeneous reactions are lifetimes and accessibilities of the radicals and interactions of solutions of monomer with fibrous cellulose. Changes in organochemical, macromolecular, and morphological structures in cellulosic fibers through formation of copolymers are made. 

The composition of the solution and its interaction with irradiated cellulosic fibers determine the increase in accessibility of these radicals. The life-times of trapped radicals in irradiated, dried (less than about 2 percent moisture) cellulose appear to be indefinite. Immersion in solutions that strongly interact with cellulosic fibers in which both their morphology and molecular orientation are changed does not necessarily scavenge or terminate all of the trapped radicals. However, immersion of irradiated cellulose in liquid ammonia reduced molecular orientation and terminated all of the trapped radicals (21, 24, 25). ... 

Morphological or supermolecular structure is the most easily changed property of cellulosic fibers. Interactions of selected monomer solutions with fibers can yield grafted products... 

Flax. Flax is also a cellulosic fiber but has a greater degree of crystallinity than cotton. The morphology of flax is quite different from that of cotton. Flax fibers have a long cylindrical shape with a hollow core. The fibers range in length from V2 to 2V2 inches, with a diameter of 12 to 16 microns. Flax staple is comprised of bundles of individual fibers. Historians believe that flax was among the first fibers to be used as... 

A porous system resulting from dispersion of a (macroscopically) continuous medium, condensation, a chemical reaction, or from any other specific process (e.g. physical or biological) may be called a growth system. Such a system usually possesses an inimitable morphology. Growth systems include the following natural or man-made porous materials pumice, cokes, activated carbon, carbon, ceolites, cellulose fibers, and finally most foamed polymers. 

Cellulose content varies. Virgin fibers produced Irom wood pulp contain 99.6% cellulose and are white. Fibers manufactured from reclaimed materials contain 75% and are gray or brown. Cellulose fibers (especially virgin materials) have a complex morphological structure which facilitates reinforcement (Figure 2.80). 

Figure 2.80. The morphology of cellulose fibers. Courtesy of Cellulose Filler Factory Corporation, Chestertown, MD, USA.

Finishing Wool Fabrics. The fundamental chemical structure of the wool fiber, together with its fiber morphology, impose an entirely different procedure in finishing wool fabrics than that outlined for the cellulosic fiber fabrics. Wool is sensitive to strong alkali, the fiber shrinks markedly with wetting, and the fiber felts under a suitable combination of mechanical work, chemical action, moisture, and heat. 

Much of the chemical behavior of cellulose fiber can be attributed to cellulose structure. Since cellulose is a highly crystalline polymer, it can absorb mechanical energy efficiently for mechanical stress reaction ( 5, 19). The mechanically activated thermal energy, in addition to rupture of main chains, may alter morphology or microstructure of cotton cellulose. Accordingly, the crystallinity and accessibility of cotton fiber may be influenced. 

The orientation of cellulosic fibers has some effect on the conductivity of the paper. The conductivity in the XY plane of the sheet (surface conductivity parallel to most of the fibers) may be quite different from the conductivity along the Z direction (bulk conductivity perpendicular to the fibers). Comparison of surface and bulk conductivity for a given paper sheet can thus yield information which reflects the anisostropy in the structural morphology due to fiber orientation. Bulk conductivity measurements are also important since many paper sheets used in reprographic processes are composed of a conductive base sheet coated with a dielectric material 16. One important specification for these types of papers is the value of the bulk conductivity of the base paper. 

In the years since controversies concerning the chemical structure of such major polysaccharides as cellulose and starch were resolved, the polysaccharide chemist has had little need for x-ray information in working out details of chemical structure. Indeed, the number of detailed x-ray studies on polysaccharides is so much smaller than the number of chemical studies that it is easy to understand why this subject has not been reviewed in this Series previously. Nevertheless, the great commercial importance of cellulose fibers and cellulose derivatives, and the influence of fiber morphology on reactivity, have resulted in a considerable volume of x-ray work relative to this particular material. A review on polymer unit-... 

One can see that a transition from rice hulls filled boards (abont 11% of a natnral mineral filler presented in rice hulls) to Biodac /rice hulls hlled boards (about 21% of combined mineral fillers) leads to 19 + 4% increase in flexnral strength and 43 + 17% increase in flexural modulus on average. This increase may be attributed not only to increase of minerals but also to morphology of Biodac porous granules and different in kind cellulose fibers in Biodac (delignihed and differently packed into the filler). 

Gauthier, R., Joly, C., Coupas, A.C. et al. (1998) Interfaces in polyolefin/cellulosic fiber composites chemical coupling, morphology, correlation with adhesion and aging in moisture. Polymer Composite, 19, 287-300. 

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