• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1102-1114
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• 2002

An electret filter is composed of permanently charged electret fibers and is widely used in applications requiring high collection efficiency and low-pressure drop. In this work, the collection efficiency of the filter media used in manufacturing cabin air filters was investigated by using poly-disperse particles when submicron particles were loaded. Long-term experiments were conducted by applying two different charging states, which were spray electrification and charge equilibrium by bipolar ionization. In order to investigate the effect of particle loading in filter media, NaCl particles were generated from 0.1% and 1% solutions by an atomizer. Liquid DOS particles were used to evaluate the effect of liquid particles on the collection efficiency of an electret filter. The results show significant effect of charge amount and size distribution of loading particles on the collection performance of a filter media in submicron region. Smaller particles loaded in electret fibers cause a more rapid degradation in collection efficiency and have lower minimum efficiency with time. The pressure drop of a filter media do rarely increase when the collection efficiency decreases to the minimum value. For the larger particles charged by spray electrification, which have charge amounts more than that of Boltzmann equilibrium charge distribution, the pressure drop of a filter media slowly increases in comparison with that of equilibrium charged particles. For DOS particles it is shown that the charging level of an electret filter severely decreases and the collection efficiency is below 10% in some particle size range.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.03a
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• pp.53-53
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• 2011

Poly(lactic acid)(이하 PLA라 칭함)는 1970-80년대의 초기 연구에서는 높은 제조비용과 희귀성에 의해 봉합사와 약물전달시스템으로 용도가 제한적이었으나 1980년대를 거쳐 1990년 이후 농업의 혁신적인 변화를 거쳐 옥수수의 다양한 측면의 이용의 하나로서 6-7년 전부터 양산화에 성공하여, 의류, 필름 및 플라스틱의 여러 가지 분야에서 적용가능성을 모색하고 있다. PLA의 장점은 석유가 아닌 천연 원료에서 얻을 수 있으며, 기존의 합성섬유와는 달리 일정한 조건하에서 미생물 등에 의해 물과 이산화탄소로 90% 이상 분해되는 친환경적인 소재이다. 합성섬유에서 의류용으로 대부분 사용되는 폴리에스테르(이하 PET라 칭함)와 유사한 물성을 가지고 있는 PLA섬유는 PET섬유와 유사한 분산염료로 염색할 수 있다. 따라서 PLA섬유는 분산염료에 의한 염색법을 중심으로 연구되어지고 있으나, PET 섬유의 융점이 $254^{\circ}C$부근인 반면, PLA섬유는 $160-170^{\circ}C$부근이다. 이로 인해 PLA를 섬유로 용도전개에 있어서 약점으로 작용하고 있다. 그러나 PLA섬유는 특유의 경량감과 새로운 촉감 등의 많은 장점을 지니고 있어 여러 가지 용도전개가 되어지고 있다. 초음파는 사람이 들을 수 없는, 사람마다 한계값은 다르지만, 주파수 약 25kHz이상의 음파를 말하며, 주파수가 높고 파장이 짧기 때문에 강한 진동을 수반한다. 초음파의 이용 원리는 Cavitation이라는 현상으로 생성된 기포가 터지면서 강력한 에너지를 방출한다. 이것은 강력하여 사방으로 퍼져 물질표면이나 내부에 영향을 미친다. 섬유에서는 표면에 뭍은 불순물을 제거하는 세정 등에 응용되고 있으며, 염색분야에서도 다양하게 연구되어지고 있다. 본 연구에서는 초음파에 의한 PLA섬유의 염색성을 조사하였다. PLA섬유를 정련하여 초음파작용의 유무에 따라 염색하여 그 결과를 고찰하였다. 초음파 작용에 따른 분산염료의 표면 색변화는 없었으며, 섬유 표면 색 농도의 차이는 초음파 작용에 의하여 저온에서는 차이가 나타나지만, 고온인 $80^{\circ}C$에서는 오히려 낮아졌다.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.470-474
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• 2010

In this study, we presents a simple microfluidic approach for generating uniform Poly(ethylene glycol)(PEG) microfiber. Elongated flow pattern of monomer induced by sheath flow of immiscible oil as continuous phase is generated in Y-shape junction and in situ polymerization by UV exposure. For uniform microfiber, we investigate the optimized flow condition and draw phase diagram as function of Ca and Qd. At the region for stable elongated flow pattern, the microfiber generated in microfluidic chip is very uniform and highly reproducible. Importantly, the thickness of microfibers can be easily controlled by flow rate of continuous and disperse phase. We also demonstrate the feasibility for biological application as encapsulating FITC-BSA in PEG microfiber.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.16-21
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• 2005

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.63-68
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• 2010

CNT and permalloy composite plating was investigated. CNTs were pretreated prior to electroplating to disassemble the tangled CNT lumps. The ball milling as a physical pretreatment and the acid treatment as a chemical pretreatment were used. 10M nitric acid and 10 M sulfuric acid were used for the chemical pretreatment. Sulfuric acid was more effective than nitric acid to disassemble CNT lumps. To disperse CNT in the solution, surfactants were used. SDS, Triton X-100 and PAA were used for this purpose. More CNTs were incorporated in permalloy coating when PAA was used as a surfactant. The surface morphologies were observed with FESEM after electroplating CNT and permalloy. The current densities were varied from 10 to $80\;mA/cm^2$ and the concentration of PAA was fixed at 2 g/L. The optimum current density without surface cracks was $20\;mA/cm^2$. The crystallinity of the deposit was analyzed with XRD and the surface hardness was analyzed with Vicker's hardness tester. The corrosion behavior was analyzed with polarization plot. The physical properties of permalloy were not improved with CNT composite plating.