Cotton fabrics were treated with polyethyleneimine (PEI), in order to cationize cellulose fibers and convert them into electro-conductive fibers by electroless plating of copper sulfide (CuS), using the introduced functional groups. As the PEI concentration increased and the treatment temperature decreased, the add-on (weight increase after treatment) of the PEI-treated fabric increased. However, treatment times of more than 30 minutes did not further affect the add-on. The PEI-treated cotton fabrics could be dyed with an acid dye, confirming that the fabrics were cationized. The apparent dye uptake according to the Mubelka-Munk equation (K/S value) of the dyed samples increased sharply with increasing PEI concentration, reached a maximum at 0.01 %(w/v), and then decreased with further increases in PEI concentration. These results indicate that a PEI concentration as low as 0.01% was sufficient for the cationization of cotton fibers. The PEI-pretreated cotton fabrics were electroless plated with CuS, using solutions containing both $CuSO_4$ and $Na_2S_2O_3$ and the electrical conductivity was compared by measuring the surface resistance. When a 4 % (w/v) $CuSO_4$ and 4 % (w/v) $Na_2S_2O_3$ solution was used for plating at $80^{\circ}C$, the CuS plated samples showed a very low surface resistance of $1-2{\Omega}/sq$. Although the maximum K/S value of the dyed fabric was obtained at 0.01% PEI concentration, the surface resistance of the samples decreased continuously, before reaching an almost constant value at the PEI concentration of 0.5%.

The gelation behavior of poly(vinyl alcohol) (PVA) solutions in dimethyl sulfoxide (DMSO) containing boric acid (BA, $H_3BO_3$) under shear stress was rheologically investigated in terms of temperature and molecular weight of PVA. Time-dependent rheological properties of the solutions were analyzed to determine the effects of stress on the gelation mechanism. The solutions of low weight-average molecular weight ($M_w=31,000-50,000$) PVA showed more noticeable temperature-dependent viscosity changes than those of high weight-average molecular weight ($M_w=165,000-186,000$) PVA. The viscosity increase caused by stress indicated that the formation of the gel structure was promoted by stress. In time sweep experiments, all the PVA solutions showed stress-dependent rheological responses except for the high $M_w$ PVA solutions at $30^{\circ}C$. The viscosities of the solutions remained constant over the observed shearing time, indicating the formation of an irreversible gel. The effects of stress history were reconfirmed by the results of frequency sweep experiments. Antecedent shearing gave rise to many different time-dependent rheological responses. At $60^{\circ}C$, both low and high $M_w$ PVA solutions had loss tangent values (tan ${\delta}$) less than 1. Furthermore, the formation of gel structures increased the relaxation time (${\lambda}$) by up to 10 s.

In this study, the effects of a compatibilizer and the blend ratio of low-density polyethylene (LDPE) on the 3D printability of polylactic acid (PLA)/LDPE monofilaments were investigated. Two kinds of PLA and LDPE with different melt indices (MI) were selected for the PLA/LDPE blend monofilaments. An ethylene/butyl acrylate/glycidyl methacrylate terpolymer, having affinities for both PLA and LDPE, was used as a compatibilizer. The tensile strength of the PLA/LDPE monofilaments decreased with increasing amounts of LDPE. PLA with a lower MI of 6 showed better printability than PLA with higher MIs of 15-30, due to its higher viscosity. When the compatibilizer was added, the compatibility and 3D printability increased. The printability increased when the compatibilizer was added up to 20 wt.%, but decreased when LDPE was added at over 30 wt.%.

Polyketone is an environmentally friendly material because carbon monoxide produced as a byproduct of other processes can be used as a raw material for its production. Polyketone has excellent heat and impact resistance, and thus it is highly applicable to industrial fabrics, such as waterproof fabrics. On the other hand, polyurethane has been used as a coating material owing to its excellent abrasion, weather, and oil resistance, in addition to being waterproof. The waterproof properties of the fabric depend on the occurrence of defects on the resin-coated surface and the adhesion strength between the coating resin and fabric. In this study, the effects of environmental conditions, including temperature and humidity, on polyurethane-coated polyketone fabric systems were evaluated. The thermal and humid aging behaviors of the polyurethane-coated polyketone fabrics were investigated with methylene diphenyl diisocyanate (MDI) pretreatment. The surface of the polyketone fabric was pretreated with MDI following treatment conditions that were optimized in a previous study. The polyketone fabric was coated with polyurethane and aged under different thermal and humid conditions. In addition to tensile and tear strength measurements, the hydrostatic pressure of the polyketone/polyurethane coating system was measured to evaluate resistance to water penetration. Additionally, the adhesion strength between the polyurethane resin and polyketone fabric after thermal aging was analyzed by the T-peel test, and the fracture surface was observed using SEM. Further, XPS was used to confirm the surface chemical change after thermal aging, and the degree of discoloration of the polyurethane-coated polyketone fabrics after aging was measured with a colorimeter.

This paper deals with the shear strengthening effect of reinforced concrete (RC) beams strengthened with high-performance fiber sheets. There are many kinds of high-performance fibers, the high-performance fibers used in this study are carbon fibers. Fifteen strengthened RC beams, including a control beam, were experimentally evaluated to determine the improvements in shear strength. Test parameters were the strengthening ratios and strengthening methods of carbon fiber sheets (I-S, I-W, U-S, and U-W type). RC beams strengthened with carbon fiber sheets were tested under four-point loads. Considering strengthening ratios and strengthening methods of carbon fiber sheets, shear capacity and failure mode of test specimens were evaluated. The results show that the shear capacity of beams strengthened with carbon fiber sheets are approximately 28.8% in I-S type, 20.5% in I-W type, 26% in U-S type, and 28.70% in U-W type higher than that of the control beam. The results of previous tests by other researchers were reviewed to evaluate the shear strength of RC beams strengthened with carbon fiber sheets. Existing equations for predicting the shear strength of such beams were examined, and a new equation based on empirical observations was proposed. The proposed equation gave accurate estimates for the 84 shear specimens evaluated.

Plasticized poly(vinyl chloride) (PVC) is widely used in industrial products because of its low price and various mechanical properties. The mechanical properties of PVC can be easily altered by adding plasticizers, changing rigid PVC into flexible PVC. However, growing concerns about the migration of phthalate-derived plasticizers, which can act as endocrine disruptors, have led to extensive research into alternative materials. In this work, plasticized PVC was prepared using acetylated citrate plasticizers and their potential to replace commercial phthalate derived plasticizers was investigated. Plasticized PVC was prepared by melt compounding the premixed plastisol using a twin-screw extruder. The compatibility of acetylated citrate plasticizers with PVC was compared with different commercial plasticizers by means of rheology and spectroscopy. The thermal stability and plasticizing ability of citrate plasticizers were evaluated using thermogravimetric analysis (TGA) and tensile modulus analysis, respectively. Acetylated citrates showed promising thermal and mechanical properties, making them a possible alternative to phthalate plasticizers.

3D printing was adopted to create a miniature human manikin. One of the disadvantages of 3D printing, especially fused deposition modeling type, is the need for a support structure for overhangs. The support structure can be waste of raw filament in a way, and also harms the surface smoothness of the final printed product. To minimize the amount of support structure, human body parts were dissected into cone-shaped segments by automatically finding bone and surface feature points. A commercial 3D printer was used and the printed manikins with and without body segmentation technique were compared quantitatively. Our cone-shaped segmentation-based printing scheme showed dramatically less amount of support structure and more smooth surfaces on most segments, except for non-cube shapes such as the head, hands, and feet.

In order to determine the sewing method suitable for smart textiles, a performance evaluation of conductive yarn according to the sewing method was conducted. The specimens were fabricated using 24 kinds of sewing methods with two lower threads, two sewing patterns, three stitch sizes, and two pattern lengths. We analyzed the following characteristics: tensile strength, resistance, and current. The tensile strength results showed that specimens sewn with cotton under thread, zigzag sewing pattern, and smaller stitch size were more stable. The electrical property evaluation showed that the temperature of the conductive yarn increased and the fabric melted when 5 V was applied to a specimen sewn with a 5 cm pattern length, Thus, it was judged that the cotton lower thread is better than polyester. The electrical properties of specimens sewn with a linear sewing pattern and larger stitch size also improved. Thus, we confirmed that specimens sewn with cotton lower thread/zigzag stitch/2 mm stitch size/10 cm pattern length are suitable for smart textiles.

A mixture of polysiloxane (PSO) and polysilazane (PSZ) was used to prepare a crosslinked organosilicon material for use as an LED encapsulant. The crosslinking was conducted by using two different chemistries: platinum-catalyzed hydrosilylation and peroxide-initiated radical reaction. Successful crosslinking was confirmed by FT-IR spectroscopy, which showed decreased intensities of vinyl ($3,100cm^{-1}$) and hydrosilane ($2,140cm^{-1}$) peaks. The prepared films showed high transparency (>90% at 400 nm) because of the high compatibility between PSO and PSZ. The crosslinked organosilicon films showed higher hardness values when both PSO and PSZ were used at the same time, indicating higher crosslinking density.