• Polymer(Korea)
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• v.26 no.4
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• pp.452-461
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• 2002

In this study, the effect of various concentrations of antioxidants on thermo-oxidative degradation of polyamide 6 was investigated. Unstabilized and stabilized polyamides 6 were subjected to long-term oven aging in ambient atmosphere at 70~$160^{\circ}C$. All of specimens were discolored within 100 hr at temperature range of 70~$160^{\circ}C$. Optimum antioxidant concentration was determined from the data of mechanical properties, yellowness index and relative viscosity. The synergistic effect of each primary and secondary antioxidant concentrations was not observed. Yellowing phenomenon was explained by using NMR, IR and EA. Different carbonyl groups were detected by $^{13}C$/NMR. During thermooxidative degradation, oxygen consumptions were determined by EA. The lifetime after long-term aging was predicted using Arrhenius equation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.1
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• pp.47-53
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• 1980

Of 1, 428 entries examined to locate gene sources resistant to Septoria brown spot from the Korean native soybean collection, most lines were evaluated as highly susceptible, showing numerous leaf spots with surrounding yellowing tissue, while 136 lines of the entries showed the leaf spots without the yellowing. However, leaf defoliation was so much higher in inoculated soybean plants than those of uninoculated, regardless of leaf yellowing that resistance to Septoria brown spot could not be characterized by the lesion type. Various yield composing characters were negatively correlated to the leaf defoliation, suggesting that early defoliation incited by Septoria brown spot might result in significant yield reduction in soybean.

• Journal of Conservation Science
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• v.30 no.2
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• pp.181-187
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• 2014

AThe studies on ceramic preservation have been conducted widely in various institutions such as national/ public museums and research labs as well as the excavation institutions and university museums. Although there are some differences in preservation methodologies and materials used across the institutions, the variation is minimal. Specifically, epoxy resin is mostly used for ceramic restoration for its high cohesiveness, low contraction and high strength although there are some variations in for Ceramic Preservation. The synthetic resin type used according to the type of damage in the ceramic. However, the yellowing or the change of color across the time after the restoration is the weakness of epoxy resin. In this study, we aim to develop a material which minimizes this yellowing of epoxy resin while enhancing its cohesiveness and strength as well as other physical properties. We made the new material to have similar properties with those used widely for the ceramic restoration, such as EPO-TEK301$^{(R)}$, L30$^{(R)}$, XTR-311$^{(R)}$ through comparative experiments. The cohesiveness of the newly developed resin was improved to 2.51(MPa), which is similar level of XTR-311$^{(R)}$ of the 2.30(MPa) but about 2x higher than the other resins EPO-TEK301$^{(R)}$, L30$^{(R)}$ (1.21 and 1.81 (MPa), respectively). Especially, the experiment on yellowing shows that the existing resins show the range of color change at 10~25(${\Delta}E^*ab$), but the new low yellowing epoxy resin has the color change value at 8.3 (${\Delta}E^*ab$), the value lowering the yellowing effect to 1 to 3 times of the existing epoxy resin, thereby solving the issue of generating sense of differences due to change of color or yellowing.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.1
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• pp.15-22
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• 1994

The formation of carbonyl group was dominant to other functional groups. Concentrations of both carboxyl and peroxide groups were found to rapidly reach low steady state values that increased slightly with increa-sing temperature and relatice humidity. Since the deg-radation of cellulose samples was in the initial stage and the conversion of glycosidic bonds and hydroxyl groups were very small, it was found that changes in the physical and chemical properties could be fitted to a first-order reaction model.

• Food Science and Preservation
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• v.18 no.2
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• pp.143-148
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• 2011

This study was conducted to investigate the effect of CA(4% $O_2$ and 7.5% $CO_2$) storage on the quality characteristics and chilling injury in 'Nanko' prunus mume fruits at 1, 5, and $9^{\circ}C$. CA storage reduced production of $CO_2$ and $C_2H_4$ significantly. Hue values of fruit skin were significantly higher in fruits stored at $1^{\circ}C$ and $5^{\circ}C$ than $9^{\circ}C$. Weight loss was much lower in fruits stored under CA storage. Soluble solids content (SSC) titratable acids (TA), and firmness were maintained and electrolyte leakage was lower in fruits stored under CA storage. Ratios of chilling injury and decay were increased faster at $5^{\circ}C$ and $9^{\circ}C$ than $1^{\circ}C$. The chilling injury was suppressed in fruits of CA storage compared with control fruits during cold storage. These results indicate that CA storage at $1^{\circ}C$ of prunus mume fruits extended the storage life up to 30 days without quality deterioration. effectively.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.47-47
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• 2011

국내의 기능성 난연성 섬유 제조기술은 원사 자체에 난연제가 포함된 상태인 난연 PET 원사나, 일반 PET 원단에 후방염 처리한 원단이 사용되기에 난연 방염성능이 만족스럽지 못하고 친환경적이지 못한 실정이다. 오늘날 세계 난연섬유 시장 규모는 10조원에 이르고 있으며 국내에서도 화재에 대한 경각심이 높아지는 추세이므로 기능성을 갖춘 고부가가치 난연소재의 개발이 시급하다. 폴리페닐렌술피드(PPS)는 내열성 및 내화학약품성이 뛰어난 열가소성 고분자로 용융방사가 가능하다. 난연성이 높은 양모섬유 또는 아크릴계 난연섬유, 아라미드 섬유 등은 비용 문제로 범용화에 한계가 있으므로 비교적 저렴한 PPS 섬유가 개발될 경우 범용화를 기대할 수 있다. 현재는 PPS 섬유가 특수한 용도에 주로 사용되고 있으나 우수한 난연 특성을 이용하여 일반 용도로의 사용 및 수요가 급격히 늘어날 것으로 예상되며 우선적으로 인테리어용 원단, 특히 커튼이나 소파용 원단으로 용도 전개가 가능할 것으로 판단하였다. 본 연구에서는 소파용 PPS 원단의 후가공 조건의 선정 및 불소계 발수방오가공을 위한 최적의 조건을 선정하고자 하였다. Padding(wet pick up율 $80{\pm}3%$)-Drying($105^{\circ}C$, 2.5min)-Curing은 시간은 1분으로 고정시킨 후, 온도를 150, 160, 170, 180, 190, $200^{\circ}C$에서 처리하여 Yellowness값을 측정한 결과, 온도가 높아질수록 Yellowness값이 커지는 것으로 미루어 보아 PPS원단은 높은 열에 영향을 받아 황변 현상이 일어나는 것으로 사료된다. 특히 $180^{\circ}C$를 기점으로 값에 큰 변화를 보였으므로 최적의 열처리 온도는 $170^{\circ}C$로 선정하여 이후의 실험을 진행하였다. 또한 큐어링 시간이 황변에 미치는 영향을 분석한 결과 온도에 의한 영향에 비해 적은 편으로 사료되었으나, 1.5min을 기점으로 Yellowess값이 높아졌으므로 최적의 열처리 시간을 1분으로 선정하였다. 최종 가공조건인 $170^{\circ}C$, 1분에서 처리한 시험포는 처리전 원단과 비교하였을 때, ${\Delta}$Yellowness가 2.84 정도로 나타났다. 그 후, PPS 원단에 불소가공제 (TG-991N, 동인텍스켐)의 적정 농도를 선정하기 위해 1~7%까지 농도를 높이며 처리한 결과, 불소가공제의 농도가 높아짐에 따라 황변현상이 나타남을 알 수 있었다. 농도가 높아짐에 따라 Yellowness값은 증가하다가 4% 이후 완만해지는 것을 알 수 있었으므로 IPA/Water Drop test와 발수도시험 (KS K 0590;2008)을 통해 적정 농도를 선정하였다. PPS 원단은 불소가공제의 농도가 높아짐에 따라 발수도가 우수해졌으며, 가공제 농도 3% 처리만으로도 우수한 발수도를 나타내었으나 100% 발수를 위해서는 가공제 농도가 5% 이상 처리되어야 하는 것을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.356-356
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• 2012

InGaN/GaN로 제작된 Blue chip의 파장에 따른 백색 LED의 성능 저하를 전기적, 광학적 특성을 고려하여 조사하였다. 4가지 파장으로 제작된 백색 LED Sample들은 60 mA, 75 mA, 90 mA의 주입 전류로 장 시간동안 스트레스를 주었다. 또한 형광체가 없는 상태와 있는 상태를 구분하여 패키지의 감쇠 특성을 확인하였다. Blue 피크 파장 437 nm, 주입전류 90 mA, 형광체가 있는 상태와 형광체가 없는 상태에서 패키지의 출력 광세기는 각각 20%, 36%까지 감소하였다. 이는 Blue Chip에서 출력되는 단파장이 페키지 몰드의 노화(황변)현상에 직접적인 영향을 주기 때문이다. 전기적 특성은 Blue chip의 파장영역에 의존하지 않고, 스트레스 시간에 따른 LED내부 저항이 커지는 현상을 확인하였다. 따라서 InGaN/GaN로 제작된 백색 LED의 장 수명을 얻기 위해서는 Blue chip의 출력 파장 영역과 페키지 몰드 재료 특성의 신뢰성 관계가 중요하다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.92-92
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• 2008

PDP의 저가화, 친환경화, 고화질화는 타 디스플레이와 경쟁을 위해 필수적이고 그로 인한 소재의 개발이 필요하다. 저가화는 부품, 공정에서도 가능하지만 소재에서의 원가가 상당부분을 차지하고 있기 때문에 소재 개발이 중요하며, 친환경화는 현재 유전체에서 많이 사용되고 있는 유해소재를 친환경 소재로 대체함으로써 개발이 이루어지고 있다. 그래서 우리는 현재 PDP에서 전극물질로 사용되어지는 고가의 Ag를 Gu입자에 Ag 박막으로 코팅한 Ag/Cu 전극 powder를 사용하여 저가의 전극 paste를 만들고 스크린 프린터와 노광장비를 사용하여 전극을 형성하였다. 그 후 친환경적인 Pb free 투명유전체를 입히고 전극과의 상호 매칭성을 연구 하였다. 결과적으로 기존 PDP 공정에서 볼 수 없었던 황변현상, 전극착색현상, 전극입자의 터짐성 등 많은 현상이 일어났지만, 기존 공정 온도보다 낮은 온도로 공정한 결과, 이러한 문제들이 줄어드는 것을 확인하였다. 이로써 공정단가의 저가화와 제품의 친환경을 가면서도 기존과 차이가 제품을 실현할 수 있을 것이다.

• Journal of Conservation Science
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• v.30 no.2
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• pp.157-168
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• 2014

This study, by selecting 3 kinds(Polish T, H, C) of metal polish being frequently used for silver archival objects treatment at present, a polish having excellent conservative property that minimizes damage of silver surface while effectively removing its yellow discolored layer by each using tool was intended to be discovered by comparing performance of tarnish inhibitor, corrosion inhibitor contained in each polish. As a result of analysis, it was confirmed that specimen that was cleaned with cotton swab and lint-free wipe by using Polish C provides not only uniformed surface expression and minimum damage but also removal function of corrosion layer. In addition, even though tarnish inhibition film should be formed after polish treatment, discolored phenomenon is unable to be prevented but among those polishes, Polish C was represented to be most stable against UV and yellowing and it showed relatively better features than that of Polish H and T in terms of hydrophobic, dispersive property. Through this, it is confirmed that Polish C would show the most excellent performance among polishes being used for conserving silver archival objects.

• Conservation Science in Museum
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• v.27
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• pp.91-102
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• 2022

Silica-based inorganic fillers for restoration of iron objects have been used for the reduction of thermal expansivity and the improvement of melt flow index. However, the higher the amount of filler is applied, the more degradation of mechanical properties and the yellowing occur, which could cause retreatment of the objects with adding stress to them. Thus, research on not only the quantification of a mixture of resin and filler but also the yellowing should be emphasized. Experiments on mechanical properties were carried out with a silica-based light filler, Micro Shell as a comparison group. The results of the experiment showed Micro Shell reduced the number of occurrences of the yellowing by 34% compared to existing fillers. The value of adhesion and specific gravity was also improved depending on the filler amount. The results of this research indicate the possibility of using Micro Shell as a new filler.