• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1367-1370
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• 2005

Microcellular foam processing of polymers requires a nucleated cell density greater than $10^9\;cells/cm^3$ so that the fully grown cells are smaller than 10 mm. A microcellular foam can be developed by first saturating a polymer sample with a volatile blowing agent, followed by rapidly decreasing its solubility in the polymer. In general, the cellular structure of crystalline polymer foams is difficult to control, compared to that of amorphous polymer foams. Since the gas does not dissolved in the crystallites, the polymer/gas solution formed during the microcellular processing is nonuniform. Moreover, the bubble nucleation is nonhomogeneous because of the heterogeneous nature of the crystalline polymer. In this paper, the effects of the crystallinity and morphology of crystalline polymers on the microcellular foam processing and on reflectivity of products are investigated. First, polymer specimens with various morphology and amount of solved blowing agent were prepared by varying the saturation pressure, saturation time and foaming condition. Then, cell morphologies according to several conditions were studied. The specimens with differing gas amount of solved and morphologies were foamed and their cellular structures were compared. The experimental results of reflectivity are compared to raw specimen and another specimen of different experimental conditions. After the experiments, recognize whether how reflectivity changes according to solved gas amount. And the effect of cell density and cell size on reflectivity is studied

• 폴리머
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• 제31권4호
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• pp.289-296
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• 2007

셀 구조는 유사하나 흡음성능에서 차이가 있는 시편을 사용하여 폴리우레탄 폼의 흡음성능을 예측할 수 있는 인자들을 FT-IR, 소각 X-선 산란(SAXS)과 dynamic mechanical thermal analyzer(DMTA)로 조사하였다. 그 결과, 전이영역에서의 damping 특성이 흡음성능과 가장 밀접한 관계가 있음을 알 수 있었다. 최근 개발된 low monol 폴리올(LMP)을 흡음용 폴리우레탄 폼에 적용할 수 있는가를 검토하기 위하여 LMP와 산화프로필렌계 폴리올(PPG)을 기본으로 한 폴리우레탄을 용액중합법으로 제조하고, 이들의 내부구조와 물리적 성질을 상호 비교하였다. Monol 성분을 다량 포함하는 PPG는 LMP에 비하여 분자 유동성이 커서 보다 발달된 상분리 구조를 보여주었다. 그러나 monol 성분에 의해 고분자량으로 성장하지 못한 분자사슬의 비효율적인 damping 거동으로 인하여 LMP의 경우가 PPG에 비하여 전이영역이 넓고, damping 양도 훨씬 더 컸다.

• 수산해양기술연구
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• 제23권4호
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• pp.157-162
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• 1987

장어통발의 P.P깔때기 살과 대나무 깔때기 살의 탄성을 측정하고 측면 구멍을 막은 통발과 원형의 유수저항, 침강시간 및 미끼의 냄새확산 등을 관찰한 다음 해상어획 시험을 행한 결과는 다음과 같다. 1. P.P 깔때기 살의 탄성은 대나무 살보다 훨씬 작고, 하중이 증가할수록 탄성회복도는 감소하였다. 2. 플라스틱 장어통발의 유수저항 R(kg)는 유속 V(m/sec)에 따라 다음 관계식으로 나타낼 수 있다. R=0.36V 상(2.01) 3. 장어통발의 침강시간은 측면 구멍을 막은 경우 수면상에서의 완전 침수까지 1~2초 정도 원형보다 지연되나 그 후의 침강속도는 거의 차이가 없었다. 4. 통발 내의 미끼 수용액은 측면 구멍을 많이 막을수록 원형보다 입구쪽으로 집중되어 확산되었다. 5. 측면 구멍을 일부 막은 통발과 원형을 가지고 어획시험을 한 결과 통발당 평균 어획미수나 평균어획량의 어획성능에 있어서 뻘로 된 어장에서는 차이가 없는 것 같다.

• 한국건설순환자원학회논문집
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• 제2권2호
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• pp.100-106
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• 2014

고강도 콘크리트는 구조적으로 우수하며 사용성 및 내구성이 뛰어나 건축물에서 그 활용성이 꾸준히 증가하고 있다. 그러나 화재처럼 고온에서 고강도 콘크리트는 폭렬이 발생될 가능성이 있으며, 폭렬 원인은 콘크리트 내부의 수증기압이 가장 큰 원인으로 알려져 있다. 콘크리트의 폭렬을 제어할 수 있는 일반적인 방법은 콘크리트 표면에 내화피복을 사용하여 화재 시 부재의 온도상승을 억제하는 방법이 있다. 이에 따라 본 연구에서는 각종 골재와 유기섬유를 사용하여 콘크리트 내화피복용 모르타르를 제조하고 그 고온 성상을 파악하고자 한다. 실험결과 퍼라이트와 폴리프로필렌 섬유를 사용한 모르타르는 내부공극과 밀도를 변화시켜 내부온도 상승을 지연시킨다. 그 결과 고강도 콘크리트의 폭렬을 방지할 수 있는 내화 피복재로 활용 가능하다.

• Journal of Biosystems Engineering
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• 제39권3호
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• pp.194-204
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• 2014

Purpose: The aim of this study was to develop long-term storage technology for Chinese cabbage in order to extend the period of availability of freshly harvested products. The scope of the paper deals with the use of a cooler with a remote monitoring and control interface in conjunction with use of packaging film. Methods: A cooler with a real time monitoring system was designed as a low-temperature storage facility to control temperature and relative humidity (RH). The effects of storage in high-density polyethylene (HDPE) plastic boxes, 3% chitosan dipping solution, polypropylene film (PEF) with perforations, and mesh packaging bags on physiological responses were investigated. The optimal storage temperature and humidity for 120 days were below $0.5^{\circ}C$ and 90%, respectively. Physiological and biochemical features of cabbage quality were also analyzed: weight loss, texture, and sugar salinity, chlorophyll, reducing sugar, and vitamin C contents. Results: The cooler with a remote monitoring and control interface could be operated by an HMI program. A $0.5^{\circ}C$ temperature and 90% humidity could be remotely controlled within the cooler for 120 days. Postharvest freshness of Chinese cabbages could be maintained up to 120 days depending on the packaging method and operation of the remote monitoring system. In particular, wrapping the cabbages in PEF with perforations resulted in a less than a 5% deterioration in quality. This study provides evidence for efficient performance of plastic films in minimizing post-harvest deterioration and maintaining overall quality of cabbages stored under precise low-temperature conditions with remote monitoring and a control interface. Conclusions: Packaging with a modified plastic film and storage in a precisely controlled cooler with a remote monitoring and control interface could slow down the physiological factors that cause adverse quality changes and thereby increase the shelf life of Chinese cabbage.

• 한국수산과학회지
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• 제51권1호
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• pp.91-94
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• 2018

We develop a time-temperature indicator (TTI) that can determine whether thawing of fish and other fishery products has occurred during frozen storage. A polypropylene tube with an internal diameter of 3 mm was prepared and cut to a length of 14 to 20 mm. One end of the tube was thermally sealed and 0.1% acetic acid was injected into the other end; the tube was then frozen at $20^{\circ}C$. Then the open side of the frozen tube was blocked by sinking the tube into a 10% gelatin solution. The tube was attached to a polyvinyl packaging bag along blue litmus paper and the bag was put into a freezer at $-20^{\circ}C$. After freezing, the bag was removed to an ambient temperature of $20^{\circ}C$, and the time dependence of the color change of the litmus paper was observed. The color changed from blue to red, with the length of the red region increasing with time. Our TTI can be used as a part of a visible detection system and the detection program can conduct the elapsed time analysis on the length of the red region of the litmus paper indicating the degree of thawing. Thus, the TTI is a useful tool in the temperature management of frozen fish and fishery products.

• 한국버섯학회지
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• 제11권4호
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• pp.297-302
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• 2013

주요 수출버섯인 큰느타리버섯의 적합한 수확 후 관리방법을 개발하기 위해 저온 저장 후 유통온도와 갈변방지처리에 따른 품질변화를 분석한 결과, 수확 후 예냉단계에서 $ClO_2$ 처리를 하여 포장하여 저온저장 후 $20^{\circ}C$ 유통시 무처리보다 신선도가 우수했으며, $10{\sim}15^{\circ}C$에서 유통할 때는 18일까지 판매가능한 신선도가 유지되어 무처리보다 3~6일 연장되어 농가에서 출하 후 매장까지 신선도 유지에는 낮은 온도관리가 가장 주요한 요인임을 확인할 수 있었다.

• 한국재료학회지
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• 제22권8호
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• pp.416-420
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• 2012

Recently nanoscience and nanotechnology have been studied intensively, and many plants, insects, and animals in nature have been found to have nanostructures in their bodies. Among them, lotus leaves have a unique nanostructure and microstructure in combination and show superhydrophobicity and a self-cleaning function to wipe and clean impurities on their surfaces. Coating films with combined nanostructures and microstructures resembling those of lotus leaves may also have superhydrophobicity and self-cleaning functions; as a result, they could be used in various applications, such as in outfits, tents, building walls, or exterior surfaces of transportation vehicles like cars, ships, or airplanes. In this study, coating films were prepared by dip coating method using polypropylene polymers dissolved in a mixture of solvent, xylene and non-solvent, methylethylketon, and ethanol. Additionally, attempts were made to prepare nanostructures on top of microstructures by coating with the same coating solution with an addition of carbon nanotubes, or by applying a carbon nanotube over-coat on polymer coating films. Coating films prepared without carbon nanotubes were found to have superhydrophobicity, with a water contact angle of $152^{\circ}$ and sliding angle less than $2^{\circ}$. Coating films prepared with carbon nanotubes were also found to have a similar degree of superhydrophobicity, with a water contact angle of 150 degrees and a sliding angle of 3 degrees.

• Elastomers and Composites
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• 제47권2호
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• pp.162-167
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• 2012

거대분자의 표면개질은 고분자재료의 물성을 향상시키기 위한 점진적이고 바람직한 방안을 제공하며 고분자의 주요 물성을 손상시키지 않고 고분자 표면의 전도도, 젖음성, 안정성, 접착 및 항박테리아성 등을 개선시킨다. PE 또는 PP 등의 polyolefin을 관능성 단량체로서 MAH와 용액상에서 그래프트시켰다. FTIR측정을 통하여 그래프팅이 일어났음을 확인하였다. 그래프팅율은 화학적정에 의하여 결정하였다. MAH량이 많아질수록 접촉각은 낮은 값을 얻었다. 또한 MAH량이 증가함에 따라 polyolefin-g-MAH의 융점($T_m$)은 감소하는 한편 분해온도($T_d$)는 증가하는 경향을 보였다.

• 멤브레인
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• 제21권4호
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• pp.351-359
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• 2011

For advanced drinking water treatment of high turbidity water, we used the hybrid process that was composed of photocatalyst packing in space of between outside of multi-channel ceramic microfiltration membrane and membrane module inside. Photocatalyst was polypropylene (PP) beads coated $TiO_2$ powder by CVD (chemical vapor deposition) process. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, standard NOM solution was prepared with humic acid and kaolin. Water-back-flushing of 10 sec was performed per every period of 10 min to minimize membrane fouling. Resistance of membrane fouling ($R_f$) increased and J decreased as concentration of humic acid changed from 2 mg/L to 10 mg/L, and finally the highest total permeate volume ($V_T$) could be obtained at 2 mg/L. Then, treatment efficiency of turbidity and $UV_{254}$ absorbance were above 96.4% and 78.9%, respectively. As results of treatment portions by membrane filtration, photocatalyst adsorption, and photo-oxidation in (MF), (MF + $TiO_2$), (MF + $TiO_2$ + UV) processes, turbidity was treated little by photocatalyst adsorption, and photo-oxidation. However, treatment portions of $UV_{254}$ absorbance by adsorption (MF + $TiO_2$) and photo-oxidation (MF + $TiO_2$ + UV) at humic acid of 4 mg/L and 6 mg/L were above 9.0, 9.5 and 8.1, 10.9%, respectively.