Ultrahigh-molecular-weight polyethylene (UHMW-PE) tapes are commercially prepared by skiving a compacted block of UHMW-PE powder. However, the mechanical properties of a skived film are poor, and the production of a thin film is difficult. In this study, we succeeded in preparing UHMW-PE tapes from UHMWPE reactor powder by multiple melt processing, i.e., melt-extrusion, melt-rolling, and melt-drawing. UHMW-PE reactor powder was continuously melt-extruded into a strand without melt fracture. The obtained melt-extruded strand was repeatedly melt-rolled at 155 and 150 ̊C in order and with stepwise reduction of the gap between the rolls to form a tape. The obtained tape (as-rolled tape) was melt-drawn at 155 ̊C to achieve high tensile strength and thin thickness. The maximum draw ratio (DR) was the highest under a strain rate of 5/min. The development of the crystalline structure of the melt-drawn tapes was investigated by wide-angle X -ray diffraction measurements and differential scanning calorimetry measurements. Extended-chain crystals (ECCs) were formed by melt-drawing of the as-rolled tape and developed with increasing DR, resulting in high tensile strength. The melt-drawn tape prepared by melt-drawing with DR of 15 under a strain rate of 5/min exhibited the most enhanced ECC formation and the highest degree of crystalline orientation, resulting in a tensile strength of 0.56 GPa and a thickness of 70 µm. Consequently, a thin UHMW-PE tape with superior tensile strength was prepared from UHMW-PE reactor powder by multiple melt processing.

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In this study, the influences of the fabric color of pantyhose (PS) on the visually perceived surface roughness were investigated. Sensory evaluations and relevant statistical analyses of the visually perceived PS surface roughness (VPPSSR) were conducted using a plate-type leg model for Japanese females; the model was covered with beige-colored PS. The visual information of the PS-covered plate-type leg model did not provide visual features usable as cues for the visual evaluation of an objectʼs surface roughness, such as a highlight pattern. The PS-covered leg models used for the sensory evaluation included eight different beige fabric colors and three different apparent colors, owing to differences in the stitch density on the leg model. Additionally,the visual features obtained via an image analysis of the PS-covered leg model were examined. As a result, it was confirmed that the VPPSSR was influenced by the apparent color of the PS-covered leg model. In conclusion, the VPPSSR in beige-colored PS is influenced by the fabric color, especially the L^* value; the brighter the fabric color, the finer the VPPSSR.

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In this study, we focused on the heat of vaporization of clothing as a method of effectively cooling body temperature. In the first place, a method using a KES thermal analysis apparatus (KES-F 7-II, Thermo Lab II) was developed for the heat of vaporization measurement in fabrics. Although the heat of vaporization measurement of fabrics has been shown to be feasible, the measurement results have been indicated to be strongly influenced by the structure of the fabrics. Therefore, it was necessary to measure each yarn in order to compare the materials and the structure of the yarn. The heat of vaporization is exactly proportional to the amount of vaporized water. Therefore, it is considered that the cooling effect depends on how much water can be vaporized per unit time. Utilizing this theory, a method for measuring the heat of vaporization of clothing could be considered. Two types of methods were developed, one is a method using a high-precision balance under no wind, and the other is a method using a thermo camera in a wind environment. It was shown that the heat of vaporization in the yarn can be measured by measuring various test samples using these measuring methods. Furthermore, the relationship between the heat of vaporization and the structure of the yarn was examined by X-ray CT measurement.

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Green composites have high specific strength and rigidity that are comparable to those of glass fiber reinforced plastics (GFRP) and other artificial fiber reinforced plastics. A recently developed unidirectional sheet of flax fibers is available as a laminate similarly to carbon fibers. Laminates generally have low strength in the thickness direction. Although Zanchor is often applied to overcome this shortcoming, Zanchor effects on the mechanical properties of green composites remain unclear. For this study, artificial entanglement was created by needle-punching of a unidirectional flax fiber sheet. Epoxy resin matrix composites were produced using hot-pressing to elucidate tensile property changes. Results show that needle-punching decreased the tensile strength and Young’s modulus in the fiber direction, although these properties increased in the direction vertical to the fiber. Furthermore, by quantifying the out-of-plane fiber orientation, we assessed effects of two fiber-orientation changes deriving from needle-punching.

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We designed a new approach to realize in situ radical polymerization of monomers without liquid solvent to obtain gel fibers using electrospinning. Poly (N-isopropylacrylamide) (PNIPAM) is one of the most studied thermo-sensitive polymers. The N-isopropylacrylamide (NIPAM) monomer was electrospun in conjugation with poly (ethylene oxide) (PEO) as a polymerization matrix. NIPAM in the electrospun nanofibers was polymerized via irradiation with UV light in the presence of a photoinitiator. The polymerization was confirmed by chemical analysis with attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and morphological observation of scanning electron microscopy (SEM) after removing monomers through washing. The anisotropy of PNIPAM fibers was controlled by the rotation speed of the collector. This approach would be useful for the medical and biological application of anisotropic PNIPAM hydrogel nanofibers, as well as in other polymers.

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