Cellulose crystallization properties

An important chemical finishing process for cotton fabrics is that of mercerization, which improves strength, luster, and dye receptivity. Mercerization iavolves brief exposure of the fabric under tension to concentrated (20—25 wt %) NaOH solution (14). In this treatment, the cotton fibers become more circular ia cross-section and smoother ia surface appearance, which iacreases their luster. At the molecular level, mercerization causes a decrease ia the degree of crystallinity and a transformation of the cellulose crystal form. These fine stmctural changes iacrease the moisture and dye absorption properties of the fiber. Biopolishing is a relatively new treatment of cotton fabrics, involving ceUulase enzymes, to produce special surface effects (15). 

Stout has written a detailed review on jute and kenaf. X-ray diffraction patterns show the basic cellulose crystal structure, although in jute and kenaf the crystalline orientation is high and the degree of lateral order is lower than in flax. Batra" in a comprehensive review has highlighted the morphological structures and physical, mechanical and chemical properties of other long vegetable fibers. 

Liu DG, Zhong TH, Chang PR, Li KF, Wu QL (2010) Starch composites reinforeed by bamboo cellulosic crystals. Bioresour Technol 101(7) 2529-2536 Lu YS, Weng LH, Cao XD (2006) Morphological, thermal and mechanical properties of ramie crystallites reinforced plasticized starch biocomposites. Carbohydr Polym 63(2) 198-204 Ma XF, Yu JG, Wang N (2007) Fly ash-reirrforeed thermoplastic starch composites. Carbohydr Polym 67(l) 32-39... 

Most work has been concentrated on the formation, structure and properties of ternary systems composed of one cellulose derivative and mixed solvents or other polymer blended solutions. Thus, the liquid crystal properties of ethylcellulose/acrylic acid, ethylcellulose/dichloroacetic acid and ethylcellulose/glacial acetic acid solutions were studied, observing the mesophase behavior when their concentrations exceeded 0.6, 0.3, and 0.35 g/ml, respectively, at room temperature [143]. Also,... 

Study of the incorporation of cellulose nanocrystals in a polyurethane elastomer shows the modification produced in the properties of the resulting material [154]. In this context, the surface hydroxyl groups on cellulose are reacted to produce modified cellulose crystals. The study reveals a strong dependence of materials properties on the cellulose content, a peculiar behavior appearing below the percolation threshold. 

Overall, cellulose I is mainly responsible for the mechanical properties of reinforced polymer composites due to its high elastic modulus and crystallinity. The elastic modulus of perfect cellulose crystals has been calculated and estimated between 130 GPa to 250 GPa, whereas the tensile strength is approximately between 0.8 GPa to 10 GPa [28]. In previous studies cellulose has already been processed into films, gels, fibers, microfibers, nanofibers and nanocrystals for different applications [29-32]. Actually, cellulose fiber is the bundle of microfibrils comprising nanocrystalline domains linking through amorphous domains [33]. 

Cellulose derivatives and polypeptides are well known to exhibit lyotropic liquid crystal properties in a large variety of solvents and only recently have been found to possess, additionally, thermotropic characteristics. 

This cycUc hemiacetal function is in an equUihrium in which a small proportion is an aldehyde which gives rise to reducing properties at this end of the chain the cellulose chain has a chemical polarity. Determination of the relative orientation of cellulose chains in the three-dimensional structure has been and remains one of the major problems in the study of cellulose. So, in the cellulose crystal, two arrangements are possible either an organisation in parallel chains with reducing chain end placed in the same side or an organisation in antiparallel chains with alternate position. 

Lima et al. extracted CNs or whiskers from different cellulose sources such as wood, cotton, and animal origins [6]. Nanowhiskers obtained from cotton are typically 8-10 nm long with diameters between 100 and 300 nm. On the other hand, tunicate nanowhiskers are 100 nm to a few microns in length and 10-20 nm in diameter. Above the critical concentration of nanowhiskers in water, ordered nanowhiskers showed liquid crystal properties. 

The bulk properties of regenerated cellulose are the properties of Cellulose II which is created from Cellulose I by alkaline expansion of the crystal stmcture (97,101) (see Cellulose). The key textile fiber properties for the most important current varieties of regenerated cellulose are shown in Table 2. Fiber densities vary between 1.53 and 1.50. 

Crystal lattice packing, 12 249-250 Crystal lattice vibrations, 14 236 Crystalline adsorbents, 1 586, 589. See also Molecular sieves Zeolites for gas separation, 1 631 properties and applications, l 588t Crystalline alkali silicates, atomic structure of, 22 454-455 Crystalline cellulose, 5 373-379 Crystalline epoxy resins, 10 373-374 Crystalline flake graphite, 12 793 manufacture and processing of, 12 781-784... 

Liquid crystal display technology, 15 113 Liquid crystalline cellulose, 5 384-386 cellulose esters, 5 418 Liquid crystalline conducting polymers (LCCPs), 7 523-524 Liquid crystalline compounds, 15 118 central linkages found in, 15 103 Liquid crystalline materials, 15 81-120 applications of, 15 113-117 availability and safety of, 15 118 in biological systems, 15 111-113 blue phases of, 15 96 bond orientational order of, 15 85 columnar phase of, 15 96 lyotropic liquid crystals, 15 98-101 orientational distribution function and order parameter of, 15 82-85 polymer liquid crystals, 15 107-111 polymorphism in, 15 101-102 positional distribution function and order parameter of, 15 85 structure-property relations in,... 

Close contact was maintained with the schools at Darmstadt where E. Berl was actively involved in the evaluation of the technical properties of cellulose and its derivatives, and Karlsruhe. Mark was an associate professor at Karlsruhe, and accordingly observed G. Bredig and A. Reis studies of the physical chemistry of colloids and crystals. 

When Herman Mark first evaluated the crystal structure of rubber (with E. A. Hauser) and cellulose (with J. R. Katz) in 1924 and 1925, it was generally accepted that these materials were low molecular weight or monomeric. The unusual properties of these substances, now known to be related to high molecular weight, were then attributed to aggolomeration or "association" of the low molecular weight precursors. A common explanation for the associations were secondary forces such as Johannes Thiele s partial valences. 

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