• Polymer(Korea)
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• v.29 no.4
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• pp.344-349
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• 2005

Polyurethanes(PUs) were synthesized by reaction of isophorone diisocyanate, acetylbutyl citrate, and 3 types of polycaprolactone diol. Their structures were confirmed by FT-IR and NMR spectrometer. And, their thermal and mechanical properties were measured by TGA ud UTM. The effective network chain lengths ($\bar{M}_c$), measured by compressive modulus apparatus, were about $8000\~24000$ g/mol. As crosslinking density and amount of hard segment increased, tensile strength increased and elongation decreased. As the crosslinking density of PUs increased, thermal property inproved. When the ratio of NCO/OH is 1.1, maximum crosslinking density was achieved.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2005.05a
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• pp.317-321
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• 2005

본 연구결과, 콜레스테롤 제거 크림치즈를 만들기 위한 유지방 함량 36%의 크림의 콜레스테롤 제거 최적 조건은 adipic acid로 가교시킨 ${\beta}-CD$ 첨가량 10%, 교반온도 $20^{\circ}C$, 교반시간 30분, 교반속도 800rpm 이었으며, 이 때 콜레스테롤 제거율은 평균 91.42%로 나타났다. 가교화 ${\beta}-CD$ 처리 크림치즈의 관능검사 결과, 가교화 ${\beta}-CD$ 처리 크림치즈는 control과 powder ${\beta}-CD$ 처리한 크림치즈에 비해 저장 기간 동안 쓴맛의 증가가 거의 없었고, 빵에 발리는 정도도 매우 우수하였으며, 전체적인 기호도 또한 높았다. short-chain fatty acid의 경우 저장 기간이 지남에 따라 가교화 ${\beta}-CD$ 처리 크림치즈는 control과 powder ${\beta}-CD$ 처리한 크림치즈에 비해 저급 지방산 생성에 변화가 거의 없었다. 조직검사에서 가교화 ${\beta}-CD$ 처리 크림치즈는 저장 기간 동안 control에 비해 응집성, 탄력성, 점착성의 변화가 없으며 그 수치가 높게 평가되었다. 또한 가교화 ${\beta}-CD$의 재활용률은 97.82%로 매우 높게 나타났다. 위 실험 결과에 따르면, 가교화 ${\beta}-CD$는 콜레스테롤 제거율이 높으며, 제품에 적용 시 품질이 향상될 뿐만 아니라, 재활용률도 높아 이를 유가공 산업에 다양하게 활용이 가능할 것으로 기대된다.

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.341-348
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• 1992

PVC was compounded with various crosslinking agents, plasticizers and acrylonitrile butadiene rubber(NBR) to evaluate their effects on the radiation gel percent, elongation at break, heat distortion and heat shrinkage. Gel yield of PVC increased with increasing unsaturation levels per molecular weight of crosslinking agents while PVC containing NBR was more sensitive to crosslinking than PVC itself regardless of the types of crosslinking agents and plasticizers. It was found that gel percent was increased with increasing radiation dose, while heat distortion was decreased with increasing gel percent. Heat shrinkage was increased with decreasing stretching temperature and increasing annealing temperature.

• 한국노년학
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• v.36 no.3
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• pp.541-562
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• 2016

The current study investigates the relationship and the mechanisms between bridge employment and change in marital satisfaction during midlife, using a three-wave panel dataset obtained from the Korean Baby Boomer Panel Study. A multivariate latent growth analysis reveals that the transition from career employment to bridge employment, compared to maintaining career employment, has an indirect negative effect on increase rate of marital satisfaction through the wage decrease. A steep decrease in wage following transition to bridge employment causes a lower increase in marital satisfaction. On the other hand, continuously engaging in bridge employment rather than career employment is associated with a higher increase in marital satisfaction via a higher increase in job commitment. This result implies that Baby Boomers adapt to bridge employment over time. Overall, the present study finds that the effect of bridge employment on the change in marital satisfaction during midlife varies with the duration of bridge employment. A future research needs to explore which factors can buffer the negative effect of decrease in wage during transition to the bridge employment on the change in marital satisfaction.

• Elastomers and Composites
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• v.43 no.1
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• pp.1-7
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• 2008

Far-infrared vulcanization of ethylene-propylene-diene terpolymer(EPDM) compounds has been studied in comparison with hot air vulcanization. Vulcanization characteristics of EPDM compounds were measured by degree of curing and temperature of specimens in vulcanization process. As a result, degree of curing by far-infrared of EPDM compounds was shown to be higher value than that by hot air at the same vulcanization temperature. Especially, degree of curing by far-infrared on 3 mm thickness of EPDM compounds was increased by two times compared to that by hot air. While the increase of thermal conductivity of EPDM compounds highly improved degree of curing by far-infrared, that hardly improved degree of curing by hot air.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.240-240
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• 2003

SiC 섬유의 고온강도를 향상시키기 위한 소결조제로 boron, aluminum 등을 사용할 수 있다. 본 연구에서는 폴리카보실란에 aluminum precursor를 첨가한 후 중합반응을 거쳐 Al-contained polycarbosilane을 합성하였다. 합성된 Al-contained polycarbosilane을 용융방사하여 섬유화 하고 열분해 공정을 통해 Si-Al-C-O 나노복합 섬유를 제조하였다. 먼저 aluminum butoxide와 polycarbosilane(commercial)을 200m1 xylene에 용해시켜 14$0^{\circ}C$에서 1시간 동안 reflux하였다. evaporator를 이용하여 xylene를 제거한 후 autoclave에서 25$0^{\circ}C$/30$0^{\circ}C$ 중합과정을 통해 가교결합 시켰다 이와 같이 합성된 시료는 ICP분석을 통해 aluminum 함량을 확인하였고 FT-IR(Fig.1) 및 GPC분석(Fig.2)으로부터 화학구조 및 분자량변화를 확인하였다. aluminum 첨가량이 증가함에 따라 Si-H/Si-$CH_3$의 결합크기의 비가 감소하였으며 이로부터 aluminum butoxide와 polycarbosilane의 가교결합이 이루어진 것으로 보이며 중합 후 분자량의 증가 또한 가교결합에 의한 결과로 사료된다 열무게감량(TGA) 측정 결과는 40$0^{\circ}C$부터 유기리간드의 분해가 일어나며 80$0^{\circ}C$이상에서 세라믹화 과정이 완료되었음을 알 수 있었다 또한 aluminum 첨가량이 증가함에 따라 세라믹 수율도 증가하였음을 확인하였다. 합성된 aluminum-contained polycarbosilane은 20$0^{\circ}C$에서 1시간 동안 불융화과정을 거쳐 환원 및 진공 분위기에서 고온 열처리하였으며 이로부터 얻어진 시료에 대해 XRD분석을 수행하였다. SEM과 TEM을 이용하여 미세구조를 관찰하였다.

• Polymer(Korea)
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• v.34 no.5
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• pp.454-458
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• 2010

In this study, the microstructural changes in orthopaedic-grade ultra high molecular weight polyethylene (UHMWPE) were compartively investigated for six different gamma-irradiation methods. Compared with un-irradiation (UGI), conventional gamma-irradiation in air room temperature (AR) induced statistically significant increases of relative crystallinity and percent crosslinking in UHMWPE. Vacuum environment (VR) during gamma-irradiation significantly increased the percent crosslinking in UHMWPE. Vacuum extreme low temperature (V77) during gamma-irradiation induced no significant changes in both relative crystallinity and percent crosslinking of UHMWPE but the percent crosslinking of UHMWPE in VR and V77 was significantly larger than that in AR. Post-irradiation stabilization process significantly increased the relative crystallinity of UHMWPE in V77, and it also significantly increased the percent crosslinking of UHMWPE in AR and V77.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.573-579
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• 1996

Crosslinked potato starches (XP), from 2,400 to 1,900 anhydroglucose units per crosslinked (AGU/CL), were prepared by reacting with epichlorohydrin. Some of the physicochemical properties of the XPs were then compared with those of native potato and cowpea starches. Crosslinking decreased moisture, protein and ash contents but had no effect on phosphorus content. Water binding capacities of the XPs increased as the degree of crosslinking increased, and that of the XP with 2,100 AGU/CL approached the value of cowpea starch. The absorption maxima of the starch-iodine complex shifted from 594 to 580 nm. Granule size increased slightly and surface appearance of the granule became rough when crosslinked. Both native and crosslinked potato starches showed B type X-ray diffraction pattern, and the relative crystallinity was not affected by crosslinking. Gelatinization temperature and the heat of gelatinization, measured by differential scanning calorimeter (DSC), did not change within the range of crosslinking tested. From X-ray and DSC data, it was concluded that the crosslinking ocurred in the amorphous region of the starch granule.

• Polymer(Korea)
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• v.29 no.5
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• pp.463-467
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• 2005

In order to enhance the actuation force of ionic polymer-metal composite (IPMC) made with the acrylic copolymer of fluoroalkyl methacryate, acrylic acie, and 2-hydroxyethyl methacrylate(HEMA), the hydroxy group of HEMA was corsslinked with 1,3-diethoxy-1,1,3,3-tetramethyldisiloxane. The water uptake was reduced and the mechanical strengths and the actuation force of the membrane was improved by crosslinking. However, current and deformation responses of IPMC were decreased by crosslinking.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.26-34
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• 2016

In this study, core-crosslinked amphiphilic polymer (CCAP) nanoparticles prepared using a reactive amphiphilic polymer precursor (RARP) were used for preparing some valuable compounds encapsulated polymer nanoparticles with high payload through nanoprecipitation process. Various solvents (acetone, ethanol, and THF) having different polarity and CCAP nanoparticles prepared using different amphiphilicity were used for the preparation of ${\alpha}$-tocopherol encapsulated polymer nanoparticles to investigate their effects on the encapsulation efficiency, payload, nanoparticle size, and stability. CCAP dissolved in hydrophobic solvent, THF, could form ${\alpha}$-tocopherol encapsulated polymer nanoparticles dispersed in water with the high payload of ${\alpha}$-tocopherol and encapsulation efficiency. Because of their physically and chemically robust nano-structure originated from crosslinking of the hydrophobic core, CCAP nanoparticles could encapsulate ${\alpha}$-tocopherol with the high payload (33 wt%) and encapsulation efficiency (97%), and form 70 nm-sized stable nanoparticles in water.