The changes in the structure of domestic (Bombyx mori) and wild (Antheraea pernyi) silk fibers when the fibers were tannin weighted have been investigated by means of the wide and small angle X-ray scattering. The crystallinity index decreased and the average crystallite size was increased by tannin-weighting. It was suggested that crystallites with smaller sizes were destroyed by tannin-weighting. With increasing tannic acid content under wet conditions, the intensity of small angle X-ray scattering decreased in domestic silk fibers, whereas it showed a maximum before decreasing monotonously in wild silk fibers. The volume fraction of microvoids and number of microvoids per unit area for dry wild silk fibers had a maximum value at a certain tannin-weighting percentage, and the average cross-section area of microvoids monotonously decreased with increasing tannin-weighting percentage. The increase in number of microvoids caused the increase in volume fraction of microvoids. Furthermore, the dyeing rate and amount of dye adsorbed at equilibrium were measured for tannin-weighted silk fibers. The diffusion coefficient of the dye was decreased by tannin-weighting. From these experimental results, the fiber structures of domestic and wild silk fibers were proposed.
Crosslinks by borate ions were introduced to improve mechanical properties of poly (ethylene-ran-vinyl alcohol) (EVOH), whose films have a very low oxygen permeability. Effects of crosslinks on the mechanical properties and oxygen permeability of the crosslinked films were studied by dynamic viscoelastic, differential scanning calorimetry, wide angle X-ray diffraction, and oxygen permeability measurements, in terms of their structural changes. The mechanical loss tangent due to the glass transition of EVOH at around 70°C was depressed and the decrease in the storage modulus above the transition temperature became less by introducing the borate crosslinks into EVOH. This indicates that the borate crosslinks are effectively formed in amorphous region and restrict the motion of amorphous chains. However, borate crosslinks prevent the crystallization of EVOH and the presence of NaOH, employed to ionize boric acid, leads to an increase in water regain in the film. Because of these effects, the oxygen barrier property became worse than that of non-treated EVOH films. Optimization of these properties is discussed by considering the preparation of gel films.
Polyester fabrics, the surfaces of which were hydrolyzed with caustic soda solution to incorporate the functional groups (-COOH) were treated with chitosan to obtain the new available functions expected. The chitosan was fixed to the surface by the reaction of these carboxyl-groups and the amino-groups of the chitosan molecules. At the same time, the chitosan films on the fibers were insolublized by the cross-linking with dicarboxylic acids. The strength of the polyester fabrics was decreased greatly by the alkali-treatment but recovered by the chitosan-treatments. One of the functions obtained with the chitosan treatment was the remarkable antistaticity.
The decolorizations of four reactive dyes with azo or anthraquinone group, printing wastewater and winch wastewater were investigated using microorganisms under anaerobic conditions. Reactive dyes with azo group were effectively decolorized. The mechanism of decolorization was suggested to be a reductive cleavage of azo bond. Decolorization rate increased in the presence of organic nutrients such as desizing wastewater. Decolorizations of printing and winch wastewaters were easily achieved as good as for azo dyes. For an artificial wastewater made from 70% of the solution of four reactive dyes and 30% of desizing wastewater, 85% decolorization and 65% COD removal were attained using anaerobic-aerobic continuous treatment.
Cellulose acetate treated with amine solutions showed relatively high affinity to direct dyes. Methylamine was found to be more efficient in improving the color intensity (K/S value) of the modified and dyed acetate substrates than di-and trimethylamines. The color intensity of dyed acetate fabrics treated with diethylamine was higher than that of fabrics treated with ethylamine and triethylamine. Dyeing of acetate samples pretreated with propylamine resulted in higher color intensity than with dipropylamine. The color intensity was found to be dependent on the acetyl content of the fabric whatever be the used amine in the treatment. The increased affinity to direct dyes could be attributed to the removal of acetyl groups and creation of new hydroxyl groups.
Dyeing behavior of Technora®, a p-aramid fiber, after treatment with organic solvents was studied. By treating with dimethyl sulfoxide (DMSO), the fiber shrinkage increased as a result of disorientation of the chains in amorphous region. Appreciable effects were not found with other solvents such as dimethyl formamide (DMF) and dimethyl acetamide (DMAC). Disperse dye (C. I. Disperse Red 60) uptake on Technora® was markedly increased by treating with DMSO under free length. Under constant length treatment, the increase in the dye uptake was much reduced. Dichroism of the dyed Technora® decreased from 0.6 to 0.33 when the fiber was treated with DMSO under free length at the temperatures 80 to 140°C. From the above results, it is concluded that fiber orientation in the amorphous region of Technora® is markedly relaxed by treatment with DMSO.
The effect of salts of ethylenediaminetetraacetic acid, EDTACaNa2 and EDTANa2, on the decrease in the damage caused to cotton during hydrogen peroxide bleaching of fabrics dyed with metal complex dyes was studied. The copper contained within the dye molecule greatly accelerated the decomposition of hydrogen peroxide. However, when EDTACaNa2 or EDTANa2 was added to the bleaching system, the decomposition of hydrogen peroxide was suppressed. The degradation of dyed fabric during the bleaching process was retarded because the chelating agents suppressed the catalytic action of the copper on the peroxide decomposition. Moreover, EDTACaNa2 suppressed the discoloration of the dyed cotton fabrics, without extracting the copper from the dye molecules on the fabric.
Cross sections of fiber were treated with enzyme and the morphological changes were observed. The objective was obtaining information with respect to the degradation of fiber by enzyme. Viscose rayon, cuprammonium rayon, polynosic rayon, cotton and cellulose acetate were selected as the fiber samples and cellulase from Trichodelma viride was used as the enzyme. The fibers were embedded into epoxy resin and their cross sections were exposed by cutting with a microtome. Morphologies of the cross section of fiber were observed by scanning electron microscopy. As for cellulose acetate, morphological change was hardly obeserbed through the treatment with enzyme for 48 h, in comparison with untreated sample. The attack by enzyme caused crack in cotton fiber, but the same morphological change was not recognized in any fibers. Regarding the regenerated cellulosic fibers which were not chemically modified, such as viscose rayon, cuprammonium rayon and polynosic rayon, the changes were different from the other fibers, due to their higher-order structures.