• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3280-3286
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• 2009

In this paper, we designed and manufactured HD Switch Panel parts with micro-etched pattern. By using CAE analysis, we could predict weld-line positions and the amount of shrinkage during injection molding process. We measured the temperature distribution of the mold surface so that we could optimize the processing conditions such as mold temperature. In order to increase the transcription of micro-etched pattern, we applied the E-Mold technology and evaluated the effect of mold temperature on the surface quality. We concluded that the etched pattern was improved(more than 2.5$\to$1.5~1.7) through the measurement of surface gloss and the observation of both SEM and SPM images.

• Journal of Adhesion and Interface
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• v.17 no.3
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• pp.96-103
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• 2016

In this work, pellets consisting of cellulose-based natural fiber bamboo and poly(lactic acid) (PLA) was prepared by extrusion process and then bamboo fiber/PLA biocomposites with various fiber contents were produced by injection molding process. The water treatment effect of bamboo fibers on the flexural, tensile, and impact properties and heat deflection temperature of the biocomposites were investigated. The thermal stability of bamboo and the flexural properties, tensile modulus, and impact strength depended on the presence and absence of water treatment as well as on the fiber content, whereas the heat deflection temperature are influenced mainly by water treatment. The increase of the mechanical and impact properties of biocomposites is ascribed to the improvement of the interfacial adhesion between the bamboo fibers and the PLA matrix by the water treatment. The result suggests that the pre-treatment of natural fibers by using water, which is environment-friendly and labor-friendly, may contribute to enhancing the performance of biocomposites.

• Elastomers and Composites
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• v.46 no.3
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• pp.204-210
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• 2011

In this study, Jute fibers reinforced polypropylene (JFRP) composites were manufactured by injection molding technique. In order to improve the affinity and adhesion between fibers and thermoplastic matrices during manufacturing, Maleic anhydride (MA) as a coupling agent have been employed. Untreated and treated surfaces of jute fibers were characterized using SEM and Fourier transform infrared (FTIR). Physical properties like water absorption rate were studied. Tensile and flexural tests were carried out to evaluate the composite mechanical properties. Tensile test and bending test indicated that JFRP composites show higher strength and modulus than pure PP. In addition, strength and modulus were found to be influenced by the variation of MAPP content (1%, 2%, and 3%). Tensile fracture surfaces were examined using scanning electron microscope. It ensures better interfacial adhesion between fibers and matrix by increasing the percentage of MAPP.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.82-87
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• 2011

Heat transfer oils are used in applications such as heating systems of chemical plant, refinery heat exchange systems, gas plant process, injection molding systems, and pulp and paper processing. These oils are extremely stable and resistance to thermal and oxidative degradation. In the event of a spill or accidental release of heat transfer oils, it can be ignite easily when there is an ignition source. This paper discusses the flammability and thermal stabilities of new and used oils. The flammability of the oils are assessed by measuring changes in flash point and auto ignition temperature. The thermal stability of oils are evaluated by the thermal screening unit ($TS^u$) and the differential scanning calorimeter (DSC). From the experimental results, it is suggested to give fire hazard characteristics to safe precautions for the proper use and treatment of heat transfer oils.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.117-124
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• 2017

In this study, we investigated the optimization of process conditions by using the Six Sigma process, design of experiment (DOE) method and response surface method (RSM) to resolve dimensional deviation and appearance problems arising from the shortened process time of the mobile phone rear cover. The analysis of the trivial many was performed by 2-sample T-test and cooling time, and mold temperature and packing pressure were selected as the vital fews affecting the overall width of the product. The optimal conditions of the process were then studied using the DOE and the RSM. We analyzed the improvement effects by applying the selected optimal conditions to the production process and the results showed that the difference between the mean value and target value of the overall width stood at 0.01 mm, an improvement of 88.89% compared to current process that fell within the range of standard dimension. The short-term process capability stood at $4.77{\sigma}$, which implied an excellent technology level despite a decrease by $0.22{\sigma}$ compared to the current process. The difference in process capability decreased by $2.44{\sigma}$ to $0.41{\sigma}$, showing a significant improvement in management capability. Ultimately, the process time of the product was shortened from 18.3 seconds in the current process to 13.65 seconds, resulting in a 34.07% improvement in production yield.

• Polymer(Korea)
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• v.36 no.4
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• pp.461-469
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• 2012

The surface modification and characterization of Ar-plasma treated polypropylene (PP) blend are investigated using x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and contact angle measurement. An increase in Ar-plasma treatment time leads to an increase in wettability, oxygen containing polar functional groups, the amount of talc, and surface roughness on the PP blend surface. A careful observation using SEM indicates that there exists a skin layer consisting of only PP component. The difference in viscosity between PP and rubber particles facilities the formation of skin layer. However, it is found that an increase in Ar-plasma treatment time helps to decrease the thickness of skin layer. Additional methodologies for the elimination of skin layer during injection molding are also discussed. The surface modification and morphological alteration induced by Ar-plasma treatment provides a hydrophilic state, followed by the improvement in wettability, on the PP blend surface.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.189-193
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• 1997

Aspheric pick-up lenses are increasingly used in consumer products such as computer and multimedia, as their mass production has become possible owing to the injection molding process. However still much work needs to be done for more effective manufacture of aspheric lenses, one area of which is the in-line inspection of produced lenses. In this paper, we present a lateral-shearing interferometer that has specially been designed to have a high immunity to external vibration and atmospheric disturbance. The interferometer comprises four prisms. They are directly attached to each other using an immersion oil so that relative sliding motions between the prisms are allowed. Their relative displacement can readily generate necessary lateral-shearing and phase-shifting to determine the wavefront of the beam collimated by the lens under inspection. A special phase-measuring algorithm of arbitrary-bucket is adopted to compensate the phase-shifting error caused by the thickness reduction in the immersion oil. Zernike polynomial fitting has done for determinating quantitative aberration of aspheric pick-up lenses. The interferometer built in this work is robust to external mechanical vibration and atmospheric disturbance so that experimental results show that it has a repeatability of less than λ/100.

• Journal of Adhesion and Interface
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• v.7 no.2
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• pp.26-31
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• 2006

In order to effectively improve interfacial adhesion strength between polypropylene (PP) and jute fiber, we particularly incorporated maleic anhydride grafted PP (MAPP) into the matrix through the environment-friendly process without an additional method of process and had better mechanical performances by providing the alignment into the natural fiber than those of the conventional fabrication technology such as an extrusion or injection molding. We also proposed hot pressing method which applied relatively low shear to the composites and confirmed the chemical bonds among the functional groups of MAPP and jute using FT-IR approach. The concentration of MAPP for maximum tensile strength and modulus was optimized at 3 wt%. Flexural properties had no noticeable tendency to increase with MAPP contents compared to tensile strength, which could probably be explained by the degree in wetting of PP/MAPP matrix.

• Journal of Adhesion and Interface
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• v.2 no.4
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• pp.24-31
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• 2001

Polypropylenes(PP) with different melt index values were mixed with ethylene-propylene rubber(EPR) or ethylene-propylene diene monomer rubber(EPDM) and an ethylene copolymer containing carboxylic acid group in a twin screw extruder. Then test specimens were prepared from the pellets of the blends with an injection molding machine. The mechanical properties and morphology of fractured surfaces were measured. Relative peak intensities of carboxylic acid group on the specimen surface were measured with an attennuated total reflection infrared spectrometer (ATR-IR) and compared with each other. The blend specimens were found to have the gradient morphology of rubber domains in PP matrix in the core region and PP skin layer. The blends containing PP of higher melt index showed greater content of ethylene copolymer containing carboxylic acid on the surface when the relative peak intensities of ATR-IR for carboxylic acid were compared. As the melt index values were increased, the decrease tendency in mechanical propeties such as tensile strength and impact strength was more significant for PP/EPR blends than PP/EPDM blends.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.710-713
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• 2005

Recently, in the area of shipbuilding, automobile and electronics, the products which electroplating was applied to are developed and put into practice in the field. The extension of the field of applications electroplated objects is to complex shape and thus the rate of faults in electroplating is being increased in the process of manufacture. On the subject of the plating process in this study, the geometric factor, which influenced electroplating, was extracted by doing a comparative analysis of the findings in the plating bath and the results of performing computer simulation of 3D. Considering these factors, the study on the optimization of designing was conducted to make the plating quantity of plated objects uniform in terms of 3D.