ABSTRACT:Contact angles of water droplet on regenerated cellulose films as an index of wettability were positively correlated with the orientation of (1-10) crystal planes and crystallinity. Because hydroxyl groups of cellulose are located at the equatorial positions of glucopyranose rings, corresponding to the surface of (1-10) crystal planes, the hydrophilicity of the (1-10) surface is expected to be very high. It is natural, therefore, that higher planar orientation of (1-10) planes and crystallinity lead to higher density of hydroxyl groups on the surface of regenerated cellulose films resulting in higher wettability. In contrast, hydrogen atoms are located at the axial positions of the glucopyranose rings, corresponding to the surface of (110) planes. Thus, the (110) surface is expected to be hydrophobic, and the surface energy obtained by computer simulations was far lower than that of the (1-10) surface. This suggests that cellulose with complementary properties, i.e., hydrophobicity, may be created by structural controls such as reversing the planar orientation from (1-
ABSTRACT:An attempt was made to disclose super-molecular structure and mechanical properties of new cellulose filament prepared from cellulose-aqueous alkali solution system. X-Ray crystallinity index Xc(X) of the new cellulose filament was far higher than those of other commercial rayons, such as viscose including polynosic and cupro and was slightly lower than the organic spun rayon. The new cellulose filament showed the lowest degree of crystal orientation among these three kinds of cellulose fibers, because of its lowest draft and stretching ratio during the spinning process. In the new filament degree of the intramolecular hydrogen bondings (I -Xam(C 3)) estimated by 13 C NMR method was highly developed. The mechanical loss tangent (tan '5) vs. temperature T curves of the new filament exhibited C( relaxation (from higher temperature side; 0( 2 , C(,h) attributed to micro-Brownian motion of the cellulose chains, two {3 ({3.1, {3. 2 ), local mode of the chains, and y, rotational mode of primary alcohol group at C6 position of pyranose rings, in the regions of T=250--100°C and -30--100°C, and near -I 00°C, respectively. Judging from the co relationships of these relaxation peak temperature T max to Xc(X) and I -Xam(C3), we concluded that there exist two amorphous regions with well-developed intramolecular hydrogen bonds but less advanced intermolecular hydrogen bonds and vice-versa in the new filament. The results of thermally stimulated currency (TSC) measurements suggested that the hydrophobic interaction among cellulose chains is tightly formed in the region with the well-developed intramolecular hydrogen bonds. In this regard, XTSc peak named here was found to correspond to mechanical relaxation C(sh· The tensile strength and elongation of the new filament were comparable to those of the regular viscose rayon. The new filament showed less swelling ratio and low fibrillation nature in water. Woven fabrics made from the filament gave some softness and high abrasion, compared with other commercial ones and were hard to wrinkle.KEY WORDS Alkali Soluble Cellulose / Filament / Supermolecular Structure / X-Ray Crystallinity / Intramolecular Hydrogen Bonds/ Viscoelastic Properties/ Mechanical Properties/ Woven Fabrics/ Authors have already established an improved cellulose dissolving technology (two step slurry method) using so-called steam-exploded pulp with average particle size of ca. 10 µm and aqueous (aq) sodium hydroxide (NaOH) solution with total concentration of ca. 7.6 wt¾, 1 based on the discovery that exploded pulp could be dissolved into aq NaOH with a specific concentration. 2 -4 In addition, all sulfite pulp, of which the degree of intramolecular hydrogen bond is always lowered by steam-explosion, has been proved to be useful as industrial resource for the above usage. 5 On the basis of the above technology authors have succeeded in manufacturing a new cellulose filament by establishing the industrially meaningful wet-spinning method (that is, the net-process where no spinning tension generates theo...
Breadmaking was performed with cellulose-blended wheat flour. Cellulose granules (7 types) of various sizes (diameter) were prepared by kneading. With increase of the blend percent of the cellulose samples from 10% to 20%, breadmaking properties such as bread height and specific volume (SV) gradually decreased in every sample; however, the decreasing levels of the properties in 7 types of various sizes varied. The decrease of bread height and SV was associated with the size of the cellulose granule. It was observed at both 10% and 20% blends that the same bread height and SV as for bread baked with only wheat flour could be obtained when the diameter of cellulose granule was above 154 mum in cellulose/wheat flour breadmaking, while they gradually decreased with granules below 154 mum. When the largest cellulose granules were mechanically ground to make smaller ones, the bread height and SV decreased with increasing grinding time. It was ascertained that the size of the cellulose granule was important for breadmaking properties. Cellulose-blended wheat flour was subjected to mixograph tests. When cellulose granules above 154-mum dia were blended with wheat flour, the profile of the mixogram was almost the same as that for wheat flour; that is, the profile had a short mixing requirement and showed a viscous gluten matrix. However, when cellulose granules below 81-mum dia were blended, a different curve showing a nonviscous dough due to breakdown of the gluten protein was observed, as ascertained by microscopy. Farmograph test showed that the amount of the released gas from cellulose-blended bread dough increased with decrease of the size of the cellulose granule due to breakdown of the gluten protein.
The behaviors of cellulose chains and cellulose mini-crystal in oil-in-water emulsions were studied by molecular dynamics simulations to investigate the coating states and the structural features of cellulose in these emulsions. In oil-in-water emulsion, dispersed cellulose chains gradually assemble during the progress of the simulation, eventually surrounding the octane droplet. In case of a cellulose mini-crystal, the cellulose chain at the corner of the crystal first contacts with the octane droplet through its hydrophobic surface. The other cellulose chains along the crystal plane then gradually move toward the octane molecules. In both emulsions, the cellulose was found to interact with both water and octane surfaces with specific conformations that allow the CH groups of the glucose rings to contact with octane molecules, while the OH groups of these rings contact with water molecules to form hydrogen bonds. The cellulose chains on the octane droplet also contact with each other through lateral hydrogen bonding between chains. These interactions stabilize the emulsion formed by cellulose molecules as surfactants.
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