The colorimetric sensor is a facile, cost-effective, and non-power-operated green energy material for gas detection. In this study, the colorimetric sensing property of a meta-aramid/dye 3 nanofiber sensor for ammonia (NH₃) gas detection was investigated. This colorimetric sensor was prepared using various dye 3 concentrations via electrospinning. Morphological, thermal, structural, and mechanical analyses of the sensor were carried out by field-emission scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and a universal testing machine, respectively. A homemade computer color matching machine connected with a gas flow device characterized the response of the meta-aramid/dye 3 nanofiber colorimetric sensor to various exposure levels of NH₃ gas. From the results, we confirmed that this colorimetric green energy sensor could detect ammonia gas in the concentration of 1–10 ppm with a sensing response time of 10 s at room temperature. After washing with laundry detergent for 30 min, the colorimetric sensors still exhibited sensing property and reversibility.

We conducted a preliminary study on fiber structural development in the high-speed melt spinning of environmentally friendly polyethylene terephthalate (Ti-PET) synthesized with 25 ppm of titanium-based catalyst, which was compared with conventional PET (Sb-PET) synthesized with 260 ppm of antimony-based catalyst. Gel permeation chromatography of Ti- and Sb-PET resins of intrinsic viscosity 0.63 confirmed that both resins have similar molecular weights and distributions. However, differential scanning calorimetry revealed that the Ti-PET resin exhibited a lower melt–crystallization peak and isothermal melt-crystallization rate than the Sb-PET resin. High-speed melt spinning of the Ti- and Sb-PET was possible up to a spinning velocity of 6 km/min. Two-dimensional wide-angle X-ray diffraction analyses showed that the molecular orientation of the obtained as-spun Ti- and Sb-PET fibers increased with spinning velocity, and a highly oriented, crystalline structure by orientation-induced crystallization started to appear from 5 km/min. Notably, Ti-PET fibers showed a lower degree of crystalline structural development and lower tensile strength compared with Sb-PET fibers under the high-speed spinning conditions. Our results suggest that the catalyst in PET resins can act as nucleating agents in thermal- and orientation-induced crystallization, and that differences in catalyst content can influence PET fiber structure development under extreme conditions in high-speed melt spinning.

High-speed melt spinning of thermotropic liquid crystalline polymer (TLCP) resin composed of 4-hydroxybenzoic acid (HBA) and 2-hydroxy-6-napthoic acid (HNA) monomers in a molar ratio of 73/27 was conducted to investigate the characteristic structure development of the fibers under industrial spinning conditions, and the obtained as-spun TLCP fibers were analyzed in detail. The tensile strength and modulus of the fibers increased with shear rate in nozzle hole, draft in spin-line and spinning temperature and exhibited the high values of approximately 1.1 and 63 GPa, respectively, comparable to those of industrial as-spun TLCP fibers, at a shear rate of 70,000 s⁻¹ and a draft of 25. X-ray diffraction demonstrated that the mechanical properties of the fibers increased with the crystalline orientation factor (f_c) and the fractions of highly oriented crystalline and non-crystalline anisotropic phases. The results of structure analysis indicated that a characteristic skin-core structure developed at high drafts (i.e., spinning velocity) and low spinning temperatures, which contributed to weakening the mechanical properties of the TLCP fibers. It is supposed that this heterogeneous structure in the cross-section of the fibers was induced by differences in the cooling rates of the skin and core of the fiber in the spin-line.

In recent years, natural disasters have been increasing worldwide due to rapid climate change, and the damage to ground structures is increasing due to the destruction of the ground. Damage to the ground structure can be reduced or eliminated by using LCP woven geotextiles as ground reinforcement. Therefore, in this study, the tensile properties, reduction factor affecting long-term performance, creep behavior, and fatigue properties of LCP woven geotextile were tested and analyzed. As a result, in the case of tensile properties, the maximum tensile strength of the LCP woven geotextile was 192.94 kN/m² in the MD direction, and it was generally constructed so that the load was transmitted. The total reduction factor is 1.86, which could be applied within 53.8% of the design strength when applied to the field. In addition, it was considered that the effect of the reduction factor for creep deformation on the long-term performance was dominant. Through the analysis of the creep behavior and fatigue characteristics, considering that the creep limit strain was 10%, if an earthquake occurred after 50 years of construction, it can be predicted that up to 90% of UTS would exhibit seismic performance. When LCP woven geotextile was applied as reinforcement, if the cyclic load due to fatigue failure was less than 478,000 times per year, it was considered that there was little possibility of the collapse of the ground structure.