• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.30 no.1
• /
• pp.63-72
• /
• 2024

Poly (butylene adipate-co-terephthalate) (PBAT) is one of the representative biodegradable polymers with high ductility and processability to replace petroleum-based polymers. Many investigations have been conducted to broaden the applications of PBAT in a variety of industries, including the food packaging, agricultural mulching film, and logistics and distribution fields. Foaming process is widely known technique to generate the cell structure within the polymer matrix, offering the insulation and light weight properties. However, there was no commercially feasible foam product based on biodegradable polymers, especially PBAT, and maintaining a proper melt viscosity of the polymer would be a key parameter for the foaming process. In this study, chemical foaming agent and cross-linking agent were introduced to PBAT, and a compression molding process was applied to prepare a foam sheet. The correlation between cell morphological structures and mechanical and physical properties was evaluated. It was found that PBAT with foam structures effectively reduced the density and thermal conductivity, allowing them to be suitable for applications such as insulation and lightweight packaging or cushion materials.

• Journal of Korea Foundry Society
• /
• v.44 no.4
• /
• pp.97-102
• /
• 2024

In this study, the properties of Zr-14Cu-7.5Ni-2.6Al wide ribbon with amorphous structure and properties were analyzed using Hall effect, SEM-EDX, and XRD. Made by melt spinning method, this Zr-14Cu-7.5Ni-2.6Al based alloy ribbon is not more than 96 ㎛ thick and 100 mm wide. This amorphous alloy exhibited tensile strength of 1,641 MPa, yield strength of 1,541 MPa, elongation of 1% and elastic modulus of 98GPa. The bulk concentration, resistivity, and mobility values are midway between general heavy doping ceramics and metals, and they are about 100 times weaker than ordinary metals, so they are close to Si and have good electrical conductivity. In addition, folding tests were conducted at extreme temperatures, withstanding 150,000 times at -20℃, 300,000 times at 24℃, and 150,000 times at 60℃, with no folding defects observed. These results demonstrate the excellent durability and reliability of the Zr-14Cu-7.5Ni-2.6Al wide ribbon alloy and suggest the possibility of developing electronic products using this alloy.

• Korean Chemical Engineering Research
• /
• v.50 no.6
• /
• pp.1068-1075
• /
• 2012

Poly(butylene terephthalate) (PBT)/Nylon6,12 core/shell micro fiber were prepared by extrusion molding. To investigate their optimum extrusion conditions, compatibility of PBT/Nylon6,12 blend micro fiber in conformity to their weight ratio and manufacture temperature was explored with SEM morphology and DSC. The alterations in their mechanical properties by extrusion speed were compared and analyzed through a UTM. In comparison with SEM figures, the domain sizes of Nylon6,12 were gradually declined by increasing the extrusion temperature of blends. Furthermore, according to these SEM images, the phase separation between Nylon6,12 domain and PBT matrix became indistinct with increasing of weight percentage of Nylon6,12. In case of DSC, the boundaries of two peaks were almost disappeared when increasing the extrusion temperature and also intervals of each two melting peaks became narrow as increasing the Nylon6,12 ratio. The mechanical properties including tensile strength, elongation, flexural strength and flexural modulus were increased as the increase in the extrusion temperature until $260^{\circ}C$. However, the mechanical properties were actually deteriorated over $260^{\circ}C$. The tensile strength, elongation, flexural strength and flexural modulus at $260^{\circ}C$ were 560 $kg_f/cm^2$, 220%, 807 $kg_f/cm^2$ and 22,146 $kg_f/cm^2$, respectively. These values are more than intermediate values of mechanical properties of PBT and Nylon6,12. These results mean that there is compatibility between PBT and Nylon6,12. Based on the extrusion conditions that produced optimum compatibility of blend, as a result, our group obtained micro fibers with the core/shell structure.

• Journal of Adhesion and Interface
• /
• v.13 no.3
• /
• pp.131-136
• /
• 2012

In this study, commercial poly(vinyl alcohol) (PVA) film was dyed with reactive dichroic dyes under mild conditions using organic solvents in stead of strong basic aqueous solution. After drawing of 500% of this PVA film, the polarizing efficiency and the single piece transmittance were measured. The degree of saponification of the commercialized PVA film was determined by using NMR and FT-IR spectromety. The commercial PVA film, with ca. 100% of the degree of saponification determined by NMR spectrometry, was dyed with the reactive dichroic dyes, which have 3,5-dichloro-2,4,6-triazine moiety. As a result, we found that the PVA film dyed with the reactive congo red showed relatively good polarization efficiency, and the PVA film dyed with the reactive direct black 22 exhibited relatively good single piece transmittance.

• Korean Journal of Materials Research
• /
• v.10 no.9
• /
• pp.629-635
• /
• 2000

The texture evolution during isothermal forging and subsequent heat treatment in Ti-48.5at%Al-0.6at%Mo alloy was investigated. Especially, in the present study, research interest was focused on the interrelation between lamellar volume fraction and textures varied with the change of heat-treated time and temperature. It was found that texture components having ND┴{302) and TD$\perp${100} with minor TD$\perp${111} were developed by isothermal forging. In addition, when the followed heat-treatment time and temperature increased from $1330^{\circ}C$/10h to $1350^{\circ}C$/20h respectively, both the lamellar volume fraction and the intensity of textures mentioned above also gradually increased. However, the tensile elongation at room temperature decreased oppositely, as the lamellar volume fraction increased. These results suggested that tensile properties of $\gamma$-TiAl with the nearly lamellar microstructure at room temperature were affected more strongly by the microstructural features such as lamellar volume fraction rather than by textures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.12
• /
• pp.285-291
• /
• 2016

The purpose of this study was to evaluate the structural capacity of steel pipe pile specimens reinforced with hollow steel plate shear connectors by pull-out test. Compressive strength testing of concrete was conducted and yield forces, tensile strengths and elongation ratios of re-bars and hollow steel plate were investigated. A 2,000kN capacity UTM was used for the pull-out test with 0.01mm/sec velocity by displacement control method. Strain gauges were installed at the center of re-bars and hollow steel plates and LVDTs were also installed to measure the relative displacement between the loading plate and in-filled concrete pile specimens. The yield forces of the steel pipe pile specimens reinforced with hollow steel plate shear connectors were increased 1.44-fold and 1.53-fold compared to that of a control specimen, respectively. Limited state forces of steel pipe pile specimens reinforced with hollow steel plate shear connectors were increased 1.23-fold and 1.29-fold compared to that of a control specimen, respectively. Yield state displacement and limited state displacement of steel pipe pile specimens reinforced with hollow steel plate shear connector were decreased 0.61-fold and 0.42-fold compared to that of a control specimen, respectively.

• Korean Journal of Materials Research
• /
• v.11 no.6
• /
• pp.512-518
• /
• 2001

It has been well known that 6.5wt% Si steel sheets have excellent magnetic properties such as low core loss. high maximum permeability and low magnetostriction. In this work, we studied a method for producing 6.5wt% Si steel sheets using a chemical vapor deposition (CVD) method. The following is the procedure adopted in this work to produce 6.5wt% Si steel sheets; SiCl$_4$ gas is applied onto a low content-Si steel sheet placed in a tube furnace. Silicon atoms resulted from the decomposition of SiCl$_4$ are permeated through the surface of the steel sheet. Finally, by the diffusion process maintaining it under a high temperature the silicon atoms diffuse uniformly into the sheet. Through this process, 6.5wt% Si steel sheets can be obtained. The manufactured Fe-6.5wt% Si steel sheet with a thickness of 0.5mm exhibited a high frequency core loss (W$_{2}$1k/) of 8.92 W/kg. Its permeability increased from 37,100 to 53,300 at 1 tesular(T). The mechanical properties of the manufactured steel sheets were also estimated and the result showed that the workability was significantly improved by annealing in vacuum at 773k. Increased plastic deformation was also observed prior to fracture and the amount of grain boundary rupture was reduced.

• Korean Journal of Materials Research
• /
• v.9 no.12
• /
• pp.1252-1262
• /
• 1999

The effect of microstructures on the strength-flangeability of Nb bearing hot-rolled high strength steel was investigated in order to improve the strength-flangeability of conventional TS 580MPa grades HSLA steel for the automotive wheel disc. The low temperature coiling method using 3-step controlled cooling pattern after hot rolling was effective to produce the Nb-bearing high strength steel with the polygonal ferrite and bainite duplex microstructures. It was suggested that the suppressed precipitation of grain boundary cementites and the decreased hardness difference between ferrite matrix and bainite cause the excellent stretch-flangeability of ferrite-bainite duplex microstructure steel. Therefore, the formation and propagation of microcracks were suppressed relative to the conventional HSLA steel with ferrite and pearlite microstructure. In addition, the elongation was improved as compared with that of hot-rolled steel sheets using conventional early cooling pattern because the volume fraction of polygonal ferrite was increased.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.4
• /
• pp.521-526
• /
• 2017

In the GTA welding process of Al 7075 alloy using different types of filler metals, the tensile test and micro-hardness test were conducted to evaluate the mechanical characteristics. Also, the radiographic test result showed that the weld met the criterion of level 1 in accordance with KS D 0242 for verifying the welding integrity and there were no welding defects. The tensile test result obtained using Al 7075 as a filler metal showed that the material was fractured in the weld zone. The tensile strengths of the materials using Al 7075 and ER 4043 as the filler metal were about 240MPa and 253MPa, their yield strengths were about 132MPa and 120MPa and their elongation percentages were 6.6% and 13%, respectively. The micro-hardness value of the deposited metal zone when using Al 7075 as the filler metal was Hv 132. However, the micro-hardness of the material using ER4043 as the filler metal was about 24% lower than that using Al 7075. When the chemical composition of the filler metal is the same as that of the material itself, fracture can occur in the deposited metal zone. Therefore, it is not desirable to use the same material as the filler metal for the welding of Al 7075 alloy. Moreover, the use of Al-Si based ER 4043 as a filler metal is more desirable than using the same material as a filler metal for welding Al 7075.

• Journal of the Korean Society for Railway
• /
• v.19 no.4
• /
• pp.417-426
• /
• 2016

In this study, the optimal welding condition of an extruded AZ61 magnesium alloy plate was investigated through evaluation of the mechanical properties and microstructure in the friction stir welding zones. The friction stir welding conditions considered in this study were the tool rotation speeds of 400, 600, and 800rpm and the welding speeds of 200, 300, and 400mm/min. To evaluate the welding strength, tensile and hardness tests were carried out. Microstructures of the welded regions were examined using optical microscopes. Under a tool rotation speed of 800rpm and welding speed of 200mm/min, the joint showed the best joining properties. The UTS, yield strength, and elongation of the welded region showed values of 79.0%, 65.4%, and 30.1%, respectively, of those of the base metal.