Yoichiro Muraoka

Water Transport Along Textile Fibers as Measured by an Electrical Capacitance Technique

A new experimental apparatus has been developed for studying water transport behavior along a bundle consisting of a few textile fibers. In order to detect the small amount of water that travels along fibers, we used an electrical capacitance technique and constructed an apparatus with a specially designed electric amplifier circuit and condenser electrodes between which sample fibers are set. We studied nylon, polyester (PET), and rayon fibers and found that there exists a minimum (critical) number of constituting fibers (CNF) when water transport occurs, depending on the fiber type. These CNF values were ten, ten, and two for nylon, PET, and rayon, respectively. We discussed these results on the basis of the wettability of the fibers.

Structure and Chemical Composition of Silk Proteins in Relation to Silkworm Diet

We investigate the structure and chemical composition of silk proteins produced by silkworms reared entirely on an artificial (A) diet, and compared those with worms entirely on a mulberry leaf ( M ) diet. The artificial diet has tofu-cake as its main component. Two types of cocoons (A and M) are used as sample materials. The dissolution behavior of the A sericin in hot water is different from that of M sericin; the amount of A sericin dissolved (28%) is higher than that of M (24%), and the dissolution rate of A sericin is also higher. Both sericins are separated into four fractions according to dissolution rate in hot water, and the amino acid composition (AAC) of each fraction is determined. Although the AAC of unfractionated A sericin is almost the same as that of M sericin, the AACs of the fractionated sericin from the A sample are distinguished from those from the M sample. AACs of the A and M fibroins are also evaluated and found to be almost identical within experimental error. The x-ray diffraction pattern of the A fibroin is also nearly the same as that of M fibroin. The artificial diet used in this study affects the dissolution behavior and chemical com position of sericin proteins, but does not affect structure and chemical composition of fibroin proteins.

Shrink-Resistant Properties and Surface Characteristics of Wool Fibers Treated with Multifunctional Epoxides

Shrink-resistant properties and surface characteristics were investigated for wool fibers treated with hydrophilic multifunctional epoxides (glycerol polyglycidyl ether—GPE). Two different reaction conditions were used for the treatment, one in a saturated NaCl aqueous solution (S sample ) and the other in the absence of NaCl (W sample). Add- on percentages of both samples were almost the same. On the other hand, both shrink- resistant properties and surface characteristics were different for these two samples, showing that the reaction medium strongly affected the reaction mode of GPE. The degree of shrink-resistance of the W sample did not improve, while that of the S sample was much improved and almost equal to Cl/Hercostt (commercially) treated wool fibers. FTIR analyses showed that the surface concentration of GPE in the S sample was lower than that in the W sample, reflecting that the hydrophobic nature of the scale surface was maintained for the S sample and not the W sample. SEM observation results revealed prominent scale edges for the W sample but not for the S sample. These results explain the differences in shrink-resistant properties for the two samples.

Physical Properties of Polyurethane Blend Dope-Coated Fabrics

We investigate the effects of the cross-sectional structure of a polyester-type polyurethane (pu)/polyvinylchloride (pvc) blend dope-coated nylon fabric on moisture permeability. The waterproof coating is applied by a one-sided wet-coagulation process. The blending of hydrophobic pvc to hydrophilic pu forms a three-layered cross-sectional structure—a pvc-rich micronetwork, a porous pu-rich layer, and the nylon fabric. As the blend ratio of pvc to pu increases, the moisture permeability (mp) and dew condensation (dc) of the coated fabrics improve. Compared to the pu homopolymer, the mp value of a pu/pvc blend in a weight ratio of 4:1 increases 1.18 times to 492 g/m2·h (JIS A-1 method) and 1.16 times to 815 g/m2·h (JIS B-1 method), but the dc value decreases one-fourth to 4.60 g/m2 · h. This gradient three-layered cross-sectional structure contributes to vapor transport properties.

Fiber Crimp Analysis by Fractal Dimension

A box-counting method for determining the fractal dimensions of crimped fibers is discussed in detail. Using nylon 6 crimped filament magnified figures, an application of the method is demonstrated where the box-counting dimension (DB ) of nylon 6 has a distribution of 1.00-1.65. Eight animal fibers, cotton, and two other synthetic crimped fibers are also characterized by DB distributions of 1.00-1.32. Modified random Koch curves are used to simulate crimped fiber shapes and to examine the relationship between Hausdorffs dimension (DH ) and DB.

Physical Properties of Wool Treated with Multifunctional Epoxides

We have investigated the physical properties of tropical wool fabrics. Samples were woven with yam from loose fibers treated with a water soluble multifunctional epoxide, i.e., glycerol polyglycidyl ether (GPE) in an aqueous medium catalyzed with a reductive agent (Na2S2O5) in the presence and absence of saturated NaCl. The resin treatment stiffened the fabrics somewhat and decreased their ability to regain moisture a little. Scanning electron microscopy revealed a difference in the abrasive breakdown pattern between the GPE/saturated aqueous NaCl treated wool and the untreated one. A good state of preservation of the hydrophobic nature of the scale surface after treatment was confirmed by soiling measurements of the wool with an oleophilic mixture/carbon black complex. There were fewer carbon black particle deposits in surfactant solution on the untreated and GPE/saturated aqueous NaCl treated wool than on the GPE/ H2O treated wool.

Measuring the Streaming Potential of Polyurethane Blend Dope-Coated Fabrics:

A new flow cell system we have designed for thin film samples is used to measure the streaming potential between two parallel films of a polyurethane (PU)/polyvinyl chloride (PVC) blend, and the ζ-potential of PU/PVC blend dope-coated nylon fabrics is then estimated. Furthermore, we propose a novel streaming potential method to directly measure coated films on the inside of the cell lid and the cell body. The ζ-potential of PVC-rich (hydrophobic) surfaces has a lower value than that of PU-rich (hydrophilic) surfaces.

Effect of Dyes on the Tensile Properties of Colored Poly(ethylene Terephthalate) Film

The effect of dye / substrate interaction on the tensile properties of colored poly(ethylene terephthalate) (PET) film has been examined. The PET is colored with anthracene (AC) and its hydroxyl derivatives ( group I dyes) as well as with anthra quinone (AQ) and its hydroxyl derivatives ( group II dyes). The offset yield stress of PET colored with anthrarobin (group IB) and with 2,6-dihydroxyanthraquinone (group II H) increases respectively by 16 and 12 MPa more than the control. After annealing, the values increase further by 7 and 5 MPa, respectively. This reinforcing effect is thought to arise from the formation of hydrogen bondings between dye and substrate, while 1-hydroxyanthraquinone (group II E) has a plasticizing effect. Dye H has a slower stress-relaxation rate than the control, whereas dye E has a faster rate. As the dye concentration in the films increases, the melting points (Tm ) of melt-quenched dye/PET mixed systems are depressed. The interaction parameter between dye and substrate X1 is obtained using Florys equation, which shows Tm depression of the systems. The values of X1 for AC and AQ are approximately zero, but other dyes have positive values. These results suggest that most of dye molecules aggregate in PET because the affinity of dyes for the substrate is inadequate. However, the values depend somewhat on the strength of the dye/substrate interaction.