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.
Super engineering plastics, such as polyetherimide (PEI), are widely used in various fields owing to their multifunctional properties. PEI is used in automobiles, electronics, and medicine owing to its high thermal resistance, excellent mechanical strength, flame retardancy, and chemical resistance. In this study, melt‐spun PEI filaments were thermally drawn and the effect of the drawing process conditions on their mechanical properties was investigated. To understand the mechanical properties of various forms, such as films, sheets, granules, tubes, and rods of PEI postprocessing, it is based on analyzing the behavior in one‐dimensional structures. The mechanical properties of the PEI filaments were dictated by the draw ratio, process temperature, and cooling temperature of the thermal drawing process. In addition, maintaining the drawing process temperature around the glass transition temperature (220°C) of PEI elongated the filament by up to 80%. Furthermore, the optimized cooling temperature was 150°C and draw ratio was 50%. In conclusion, PEI filaments with excellent mechanical properties were obtained by optimizing the draw ratio, process temperature, and cooling temperature of thermal drawing. Through the behavior of the molecular and crystal structures by thermal drawing of PEI filament, it is expected to be applied to two‐ or three‐dimensional structures.
Flash-spun nonwoven (FS-NW) is gaining attention in the PPE field due to its excellent barrier and mechanical properties resulting from its non-uniform diameter distribution and unique filament morphology. The unique network structure of flash-spun filaments (FSF) comprising the FS-NW can be controlled by phase separation behavior in the supercritical fluid (SCF) process. This study proposes a simple method to control the microstructure of FSFs by controlling the pressure-induced phase separation (PIPS) process in polymer/SCF solution. This phase separation behavior of an HDPE/SCF solution was confirmed by using a high-pressure view cell. A multistage nozzle allowing for phase-separated pressure to form different phases was also designed. HDPE-FSFs were synthesized by flash-spinning, and their morphology, crystallinity, and mechanical properties were investigated. The results demonstrated that the filaments obtained by PSP control at 220 °C and with an HDPE concentration of 8 wt% showed a network structure composed of strands, wherein the diameters ranged from 1.39 to 40.9 μm. Optimal FSF was obtained at 76 bar, with a crystallinity of 64.0% and a tenacity of 2.88 g/d. The PIPS method can thus effectively control the microstructure more feasibly than temperature- or solvent-induced techniques and can allow the effective synthesis of various products.
The cotton yarn was subjected to bio-polishing treatment with three commercial enzymes(Cellusoft L, Denimax-991L and Denimax-acid) to remove the fuzz on the cotton yarn. Also, enzyme treated cotton yarns were compared with singeing cotton yarns. Experimental variables of enzyme treated cotton yarn were as follow: concentration of enzyme solution and NaOH, dipping time, and processing temperature. The enzymatic treatments were evaluated by analyzing the effect on yarn count, twist contraction, evenness and tenacity. As the results, enzymatic treatment on cotton yarn induced same effects as the traditional singeing treatment. Also, silket treatment of cotton yarn after bio-polishing enhanced the tensile properties of the cotton yarn.
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