• 한국산업보건학회지
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• 제32권2호
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• pp.153-162
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• 2022

Objectives: Fused deposition modeling (FDM) 3D printer which is one of the material extrusion (MEX) technologies is an additive manufacturing (AM) process. 3D printers have been distributed widely in Korea, particularly in school and office, even at home. Several studies have shown that nanoparticles and volatile organic compounds (VOCs) were emitted from an FDM 3D printing process. The objective of this study was to identify types of chemicals possibly emitted from FDM 3D printing materials such as PLA (polylactic acid), ABS (acrylonitrile butadiene styrene), nylon, PETG (polyethylene terephthalate glycol), PVA (polyvinyl alcohol), PC (polycarbonate) filaments. Methods: 19 FDM 3D printing filaments which have been distributed in Korea were selected and analyzed VOCs emitted of 3D printing materials by headspace gas chromatography mass spectrometry (headspace GC-MS). Subsamples were put into a vial and heated up to 200℃ (500 rpm) during 20 minutes before analyzing FDM 3D printing filaments. Results: In the case of PLA filament, lactide and methyl methacrylate, the monomer components of one, were detected, and the volume ratio ranged 27~93%, 0.5~37% respectively. In the case of ABS filaments, styrene (50.5~59.1%), the monomer components of one, was detected. Several VOCs among acetaldehyde, toluene, ethylbenzene, xylene, etc were detected from each FDM 3D printing filaments. Conclusions: Several VOCs, semi-VOCs were emitted from FDM 3D printing filaments in this study and previous studies. Users were possibly exposed to ones so that we strongly believe that we recommend to install the ventilation system such as a local exhaust ventilation (LEV) when they operate the FDM 3D printers in a workplace.

• 한국해양바이오학회지
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• 제14권2호
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• pp.133-142
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• 2022

The increased production and consumption of polyethylene terephthalate (PET)-based products over the past several decades has resulted in the discharge of countless tons of PET waste into the marine environment. PET microparticles resulting from the physical erosion of general PET wastes end up in the ocean and pose a threat to the marine biosphere and human health, necessitating the development of new technologies for recycling and upcycling. Notably, enzyme-mediated PET degradation is an appealing option due to its eco-friendly and energy-saving characteristics. PETase, a PET-hydrolyzing enzyme originating from Ideonella sakaiensis, is one of the most thoroughly researched biological catalysts. However, the industrial application of PETase-mediated PET recycling is limited due to the low stability and poor reusability of the enzyme. Here we developed the whole-cell catalyst (WCC) in which functional PETase is attached to the outer membrane of Escherichia coli. Immunoassays are used to identify the surface-expressed PETase, and we demonstrated that the WCC degraded PET microparticles most efficiently at 30℃ and pH 9 without agitation. Furthermore, the WCC increased the PET-degrading activity in a concentration-dependent manner, surpassing the limited activity of soluble PETase above 100 nM. Finally, we demonstrated that the WCC could be recycled up to three times.

• 센서학회지
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• 제31권2호
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• pp.90-95
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• 2022

The effect of the structure of an ITO nanoparticle film sensor on its performance was studied. A printed ITO film (P-ITO film) was fabricated on a flexible polyethylene terephthalate (PET) substrate, and the contact resistance of the electrode and sensor response change were clarified according to the detection position. The contact resistance between Ag and P-ITO was observed to be -204.4 Ω using the transmission line method (TLM), confirming that a very good ohmic contact is possible. In addition, we confirmed that the contact position of the analyte had a significant influence on the response of the sensor. Based on these results, the performance of the four types of sensors was compared. Consequently, we observed that 1) optimizing the resistance of the printed film, 2) optimizing the electrode structure and analyte input position, and 3) optimizing the electrode area are very important for fabricating a metal oxide nanoparticle (MONP) sensor with optimal performance.

• 한국염색가공학회지
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• 제35권2호
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• pp.128-136
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• 2023

Recently, the automobile industry is developing as the demand for automo- biles increases due to industrial development and population growth. In addition, many studies are being conducted to reduce heat loss inside the automobiles in order to save energy inside the automobiles due to environmental regulations. In this study, alumina, nanosilicon, and aerogel, which are adiabatic materials, were filled in PET to manufacture yarn, identify physical and mechanical properties, and weave into fabric to confirm adiabatic performance. As the content of the adiabatic material increased, the tensile strength of the fibers filled with alumina and nanosilicon decreased greatly, and the adiabatic property slightly increased. The tensile strength of fibers filled with the aerogel decreased slightly, but the adiabatic properties were greatly increased. Therefore, it is considered to be due to the large volume fraction in the PET yarn due to the low density of the aerogel.

• Asia Marketing Journal
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• 제14권3호
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• pp.169-184
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• 2012

All firms require new stimulus to spurt growth. Therefore it is necessary to successfully develop new products and to employ appropriate marketing practices for the new products to enter and settle in the market. Binggrae, a Korean company that specializes in dairy and processed dairy products, introduced a ready-to-drink (RTD) coffee product, 'a Café la' to expand its business into the coffee market in 2008. Binggrae was a latecomer in the RTD coffee market but a Café la has shown an impressive average sales growth rate of 115% as of 2011 since the launch. Moreover, it is a steady bestselling coffee brand among the Polyethylene terephthalate (PET)bottle category. Binggrae found potential and opportunity in the growing coffee market and made efforts to develop a new product that can be differentiated from the existing products. The result was PET bottle coffee, which was more portable and convenient to drink than coffee products offered in cups or cans. PET bottle coffee is produced through the patented Aseptic Filing System, thus the original coffee flavor stays fresh when combined with milk and has a longer shelf life than coffee products in cups. Moreover, as the taste of coffee consumers has become more sophisticated, Binggrae developed a premium product by differentiating the product processing method and by using higher-quality Arabica beans. After launching the new product, the company also employed a well-designed communication strategy. First, Binggrae was able to confirm the level of market demand and market potential for the product by employing BTL (Below the Line) marketing strategies through the consumers' word-of-mouth. Afterwards, the company invested its resources for a full-scale ATL (Above the Line) marketing campaign. Later a Café la's TV commercial effectively portrayed the product's characteristics, and succeeded in raising consumer awareness of the product. As a result, a Café la has become the bestselling brand in the PET bottle coffee market. The successful new product marketing strategy of Binggrae'sa Café la offers many valuable implications for companies planning to launch new products in the future.

• 한국의류산업학회지
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• 제25권5호
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• pp.651-660
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• 2023

This study aimed to research the local production of conductive composite yarn, a source material used in textile-type electrodes and circuits. The physical properties of an internationally available conductive composite yarn were analyzed. To manufacture the conductive composite yarn, we selected one type of conductive yarn with Ag-coated polyamide of 150d 1 ply, along with two types of polyethylene terephthalate (PET) with circular and triangular cross-sections, both with 150d 1 ply. The conductive composite yarn samples were manufactured at 250, 500, 750, and 1000 turns per meter (TPM). For both conductive composite yarn samples manufactured from two types of PET filaments, the twist contraction rate of the sample with a triangular cross-section was stable. Among the samples, the tensile strength of the sample manufactured at 750 TPM was the highest at approximately 4.1gf/d; the overall linear resistance was approximately 5.0 Ω/cm, which is within the target range. It was confirmed that the triangular cross-section sample manufactured with 750 TPM had a similar linear resistance value to the advanced product despite the increase in the number of twists. In future studies, we plan tomanufacture samples by varying the twist conditions to derive the optimal conductive yarn suitable for smartwear and smart textile manufacturing conditions.

• Tribology and Lubricants
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• 제39권6호
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• pp.235-243
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• 2023

This paper presents the fabrication process of water-lubricated plastic bearings. Plastic bearings require good mechanical properties and tribological properties as well as elasticity and shock resistance, especially when lubricated in dirty water conditions. In this study, sleeve-type plastic bearings are produced by winding a prepreg sheet, which primary contains nitrile rubber (NBR)-modified epoxy, self-lubricating fillers, and various types of lattice-structured reinforcing fibers such as carbon, Aramid, and polyethylene terephthalate. A thermosetting epoxy is chemically modified with NBR to impart elasticity and low-friction characteristics in water conditions. Experimental investigations are conducted to examine the mechanical and tribological characteristics of the developed bearing materials, and the results are compared with the characteristics of a commercial plastic bearing (Thordon SXL), well known as a water-lubricated bearing. A Thordon bearing (mainly composed of polyurethane) exhibits an extremely low load-bearing capacity and is thus only suitable for medium loading (1~10MPa). The tribological characteristics of the test materials are evaluated through Falex block-on-ring (LFW-1) friction and wear tests. The results indicate that friction exhibited by the carbon-fiber-reinforced NBR-10wt.%-modified epoxy composite material, incorporated with the addition of 20wt.% UHMWPE and 6wt.% paraffin wax, is lower than that of the Thorden bearings, whereas its wear resistance surpass that of Thorden ones. Because of these features, the load carrying capacity of the fabricated composite (>10MPa) is higher than that of the Thorden bearings. These results confirm the applicability of water-lubricated plastic bearing materials developed in this study.

• 한국결정성장학회지
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• 제34권1호
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• pp.16-21
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• 2024

전기변색(electrochromic devices, ECD) 방식을 이용하여 외부 전압 인가에 의해 착색된 상태에서 투명한 상태로 색 변화를 일으킬 수 있는 필름 형태의 스마트 윈도우를 제조하였다. 기존 유리 대신 투명 PET 필름을 기재로 사용하였고 ITO/Ag/ITO 전극층, WO3/TIC2 유기변색층, Nafion 전해질층을 차례로 도입한 이후 합지 공정을 통하여 총 두께가 50 ㎛ 정도인 다층 박막 ECD 모듈을 제조하였다. 길이가 80 mm 이상인 대면적의 ECD 모듈을 제조하기 위하여 스퍼터링, 바코팅, 열압축 공정을 최적화하였다. 보통 상태에서 54 % 수준의 투과율을 보였으나 DC 3.5 V의 전압을 인가했을 때 24 %까지 떨어졌으며 색 변화는 육안으로도 확인할 수 있었다. 가역적인 색 변화에 의해 외부 태양광을 선택적으로 차단할 수 있으며 냉난방에 필요한 에너지 저감 측면에서 효과적일 것으로 예상된다.

• Design & Manufacturing
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• 제18권2호
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• pp.17-22
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• 2024

Lightweight of plastic containers is becoming an important issue due to increasing environmental legislation and consumer awareness. In this study, the CAE analysis was conducted to optimize the shape of a 500 ml lightweight square polyethylene terephthalate(PET) bottle. First, the linear buckling alaysis using the finite element method was performed to analyze the correlation between the primary geometric parameters of the bottle and the buckling critical load. Then, the optimal geometry parameters were derived, and the actual buckling load was predicted by non-linear buckling simulation. The validity of the simulation results was verified by top-loading tests of PET bottles molded with the optimized geometry. The elastic modulus and tensile yield strength of PET through tensile tests were measured to improve the accuracy of the simulation. As a result of the tensile tests, the modulus of elasticity of PET increased from 2,900 MPa to 4,275 MPa, and the tensile yield strength increased from 52.4 MPa to 88.1 MPa. Finally the buckling load of the optimized PET bottle was found to be approximately 236 N, which is very similar to the simulation precition of 238 N. This study shows the feasibility and accuracy of the CAE analysis approach for the lightweight design of PET bottles, and will provide useful guidelines for the design of PET bottles.

• 대한환경공학회지
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• 제27권9호
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• pp.946-951
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• 2005

본 연구에서는 청정 호발공정의 하나로 플라즈마 처리를 사용하였다. 폴리에스테르(polyethylene terephthalate, PET) 직물에 가호된 폴리비닐 알콜(polyvinyl alcohol, PVA), 아크릴 호제(polyacrylic acid esters, PACL)과 이들의 혼합된 호제들을 질소($N_2$)와 산소($O_2$) 플라즈마로 처리하였다. 호제제거에 있어서 산소 플라즈마가 질소 플라즈마 보다 더 효과적이었으며, PACL 보다는 PVA 호제 제거가 더 우수하였다. 플라즈마 처리된 시료의 주사전자현미경(scanning emission microscopy, SEM) 사진을 통하여 호제들이 제거되었음을 직접 확인할 수 있었다. 산소 플라즈마 처리 후, 기존의 습식공정을 이용하여 폴리에스테르 직물을 호발하였다. 플라즈마로 처리하지 않은 직물과 비교하여 산소 플라즈마 처리된 직물의 호발폐수는 더 낮은 TOC, COD와 $BOD_5$ 값을 보여주었다. 이것은 플라즈마 처리가 직접적으로 호제를 제거할 수 있을 수 뿐 아니라 호제의 화학적 특성을 변화시킴으로서 이점을 제공할 수 있다는 것을 보여준다. 마지막으로, 플라즈마 처리에 의한 호발 공정이 폴리에스테르 직물의 염색성에 미치는 영향을 색차와 염색견뢰도를 측정하여 살펴보았다. CCM(computer color matching) 측색 실험 결과, 산소 플라즈마로 20분간 처리한 폴리에스테르 직물과 기존 습식공정으로 호제가 제거된 기준직물과의 색차값은 1 정도이었다. 이것은 다른 부수적인 공정 없이 플라즈마로 처리된 직물이 바로 염색공정에 사용될 수 있다는 것을 나타낸다. 또한, 플라즈마로 처리된 직물은 좋은 염색견뢰도 결과를 보여주었는데, 세탁견뢰도, 마찰견뢰도, 승화견뢰도, 일광견뢰도도 기준직물과 비교하여 같거나 더 우수하였다.