• 한국건설순환자원학회논문집
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• 제7권3호
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• pp.187-193
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• 2019

미세먼지의 물리적 흡착기구에서 다공질 매체의 공극구조 연결성은 매우 중요한 인자이다. 본 연구에서는 플라이애시 기반의 지오폴리머를 기본 매체로 하고, 내부에 유기 생분해성 섬유재를 매립하여 강알칼리에 용해한 뒤 내부 연결 공극을 가지는 조직을 제조하였다. 다양한 배합을 통하여 압축강도는 20MPa 이상을 확보하였지만 NaOH 5mole 및 $30^{\circ}C$에서는 PLA가 거의 용해되지 않았으며, 온도의 증가에 따라 PLA 용해속도는 급격히 증가하였다. 비즈 타입의 PLA 섬유가 온도 $90{\sim}130^{\circ}C$ 및 NaOH 5~12mole 조건에서 24시간 이내에 모두 용해하는 것을 확인하였는데, 상온에서의 FA 기반 지오폴리머의 경우 반응성이 거의 없으므로 용해된 섬유내의 공간은 유효할 것으로 판단된다. 이러한 내부 공극연계구조는 미세먼지의 흡착 및 저장에 유리할 것으로 예상된다.

• Advances in nano research
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• 제4권1호
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• pp.15-29
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• 2016

A low cost environmentally benign surface coating binder is highly desirable in the field of material science. In this report, castor oil based hyperbranched polyester/bitumen modified fly ash nanocomposites were fabricated to achieve the desired performance. The hyperbranched polyester resin was synthesized by a three-step one pot condensation reaction using monoglyceride of castor oil based carboxyl terminated pre-polymer and 2,2-bis (hydroxymethyl) propionic acid. Also, the bulk fly ash of paper industry waste was converted to hydrophilic nano fly ash by ultrasonication followed by transforming it to an organonano fly ash by the modification with bitumen. The synthesized polyester resin and its nanocomposites were characterized by different analytical and spectroscopic tools. The nanocomposite obtained in presence of 20 wt% styrene (with respect to polyester) was found to be more homogeneous and stable compared to nanocomposite without styrene. The performance in terms of tensile strength, impact resistance, scratch hardness, chemical resistance and thermal stability was found to be improved significantly after formation of nanocomposite compared to the pristine system after curing with bisphenol-A based epoxy and poly(amido amine). The overall results of transmission electron microscopic (TEM) analysis and performance showed good exfoliation of the nano fly ash in the polyester matrix. Thus the studied nanocomposites would open up a new avenue on development of low cost high performing surface coating materials.

• Journal of Ginseng Research
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• 제37권4호
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• pp.435-441
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• 2013

This study investigated the effects of Korean Red Ginseng (KRG) on radiation-induced bone loss in C3H/HeN mice. C3H/HeN mice were divided into sham and irradiation (3 Gy, gamma-ray) groups. The irradiated mice were treated for 12 wk with vehicle, KRG (per os, p.o.) or KRG (intraperitoneal). Serum alkaline phosphatase (ALP), tartrate-resistant acid phosphatase, estradiol level, and biomechanical properties were measured. Tibiae were analyzed using micro-computed tomography. Treatment of KRG (p.o., 250 mg/kg of body weight/d) significantly preserved trabecular bone volume, trabecular number, structure model index, and bone mineral density of proximal tibia metaphysic, but did not alter the uterus weight of the mice. Serum ALP level was slightly reduced by KRG treatment. However, grip strength, mechanical property, and cortical bone architecture did not differ among the experimental groups. The results indicate that KRG can prevent radiation-induced bone loss in mice.

• Elastomers and Composites
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• 제40권1호
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• pp.59-65
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• 2005

메타크릴산의 아연염인 ZMA를 EPDM고무와 직접 블렌딩하거나 또는 ZnO와 MAA의 형태로 첨가한 후 이들간의 중화반응을 유도하여 고무에 in-situ로 형성시키는 방법을 이용하여 EPDM/ZMA 복합체를 제조하였다. 인장시험, 인열시험, 열노화시험 결과 ZMA의 첨가는 EPDM의 기계적 물성 및 열노화에 대한 안정성을 현저히 향상시킬 수 있음을 알 수 있었다. 또한 ZMA의 첨가는 EPDM고무와 금속과의 접착력을 크게 향상시킬 수 있음을 알 수 있었다. 이러한 기계적물성 및 접착물성의 향상효과는 과량의 ZnO를 사용한 중화반응에 의해 ZMA를 형성시킨 복합체에서 더욱 크게 나타났다. 이는 ZMA의 도입에 의한 이온가교결합의 형성 및 고무매트리스에서의 ZMA 도메인의 분산도와 연관되는 것으로 판단되었다.

• Elastomers and Composites
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• 제35권3호
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• pp.205-214
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• 2000

TDI에 PPG 3000을 기재로 사용하고 PPG 400, PPG 1000, PPG 2000을 $0{\sim}50%$ 혼합 사용하여 프리폴리머형 폴리우레탄수지를 합성한 후 합성 내용을 분석하고 합성물의 물성을 조사하였다. 반응은 촉매를 합성 초기에 넣었을 때에는 글리콜이 TDI 적하시에 대부분 반응되어 점도의 급상승이 일어나 불안하였지만 $40^{\circ}C$에서 무촉매 상태로 TDI를 적하시킨 후 $60^{\circ}C$ 승온 후에 촉매를 넣었을 때에는 매우 안정하였다. 인산을 사용하면 $40^{\circ}C$에서 부반응이 억제되어 점도는 낮아지지만 경화반응시 입체적으로 가교되지 못해 가교속도는 느리게 나타났다. 경화속도는 NCO/OH의 비보다는 분자의 입체적 구조에 더 영향을 받았다. 접착력은 글리콜 성분 중에 PPG 400을 적어도 30%(wt.%) 이상 사용하였을 때 PPG 400에 의한 가교밀도 상승으로 보다 우수한 물성을 나타내었다.

• 한국분말재료학회지
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• 제26권4호
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• pp.282-289
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• 2019

Ti has received considerable attention for aerospace, vehicle, and semiconductor industry applications because of its acid-resistant nature, low density, and high mechanical strength. A common precursor used for preparing Ti materials is $TiCl_4$. To prepare high-purity $TiCl_4$, a process based on the removal of $VOCl_3$ has been widely applied. However, $VOCl_3$ removal by distillation and condensation is difficult because of the similar physical properties of $TiCl_4$ and $VOCl_3$. To circumvent this problem, in this study, we have developed a process for $VOCl_3$ removal using Cu powder and mineral oil as purifying agents. The effects of reaction time and temperature, and ratio of purifying agents on the $VOCl_3$ removal efficiency are investigated by chemical and structural measurements. Clear $TiCl_4$ is obtained after the removal of $VOCl_3$. Notably, complete removal of $VOCl_3$ is achieved with 2.0 wt% of mineral oil. Moreover, the refined $TiCl_4$ is used as a precursor for the synthesis of Ti powder. Ti powder is fabricated by a thermal reduction process at $1,100^{\circ}C$ using an $H_2-Ar$ gas mixture. The average size of the Ti powder particles is in the range of $1-3{\mu}m$.

• 접착 및 계면
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• 제22권2호
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• pp.39-46
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• 2021

가지형 구조의 3-Methyl-1,5-pentanediol (MPD)을 함유한 폴리에스테르 폴리올 및 폴리카보네이트 폴리올을 이용하여 수분산 폴리우레탄(WPU)을 합성하였다. 물리적 특성 비교를 위하여 1,4-butanediol (BD)과 adipic acid로부터 얻어진 폴리에스테르 폴리올 및 1,6-hexane diol (HD)/ 1,4-butanediol (BD)로부터 얻어진 폴리카보네이트 폴리올을 이용하여 수분산 폴리우레탄 수지를 합성하였다. 본 연구는 폴리올 분자구조(소프트 세그먼트의 분자구조)가 WPU의 물리적 특성에 미치는 영향을 조사하였으며, MPD가 함유된 폴리올을 이용하여 합성된 WPU의 경우가 MPD를 함유하지 않은 경우보다 100% 탄성률 및 인장 강도는 낮게 나타났으며, 신장률은 높게 나타났다. MPD 성분을 함유한 WPU 필름의 투명도는 MPD 성분을 함유하지 않은 WPU 필름보다 광 투광도가 우수함을 알 수 있었다.

• Animal Bioscience
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• 제34권3_spc호
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• pp.371-384
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• 2021

Objective: Wheat bran (WB) was co-fermented with Aspergillus oryzae and phytase (Phy) to determine whether co-fermentation improve WB phosphorus and fiber utilization in Isa-brown layers. Methods: A total of 112 Isa brown layer were randomly divided into 7 treatments with 8 replicates per a treatment and 2 hens per a replicate. The treatments included basal diet (control), basal diet supplemented with 250 unit/kg Phy (control+Phy), diet with 10% WB (10% WB), diet with 5% WB and 250 unit/kg Phy (5% WB+Phy) diet with 10% WB and 250 unit/kg Phy (10% WB+Phy), diet with 5% fermented WB supplemented with molasses and phy (PCFWH) and 125 unit/kg Phy (5% PCFWH), and diet with 10% PCFWH (10% PCFWH). The intestinal microbial population, intestinal morphology, serum antioxidant enzyme activities, and excreta phosphorus content were assessed. Results: In PCFWH, spore counts, protease activity, xylanase activity, and ferulic acid were 8.50 log/g dry matter (DM), 190 unit/g DM, 120 unit/g DM, and 127 ㎍/g, respectively. Xylobiose and xylotriose were released in PCFWH, while they were not detectable in WB. Antioxidant capacity was also enhanced in PCFWH compared to WB. The 10% WB+Phy and 10% PCFWH groups produced higher egg mass, but hens fed 5% WB+Phy had the lowest amount of feed intake. Eggs from 10% PCFWH had better eggshell weight, eggshell strength, and eggshell thickness. Birds fed with 10% PCFWH also had higher serum superoxide dismutase and catalase activities. Compare to control, 10% PCFWH significantly reduced excreta phosphorus content. Conclusion: Diet inclusion of 10% PCFWH improved egg quality, antioxidant status, and excreta phosphorus content of laying hens.

• International Journal of Industrial Entomology and Biomaterials
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• 제45권2호
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• pp.56-69
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• 2022

Silk is a unique natural biopolymer with outstanding biocompatibility, high mechanical strength, and superior optical transparency. Due to its excellent properties, silk has been widely reported as an ideal biomaterial for several biomedical applications. Recently, fluorescent silk protein, a variant of native silk, has been reported as a biophotonic material with the potential for bioimaging and biosensing. Despite the realization of fluorescent silk, the traditional degumming process of fluorescence silk is crude and often results in fluorescence loss. The loss of fluorescent properties is attributed to the sensitivity of silk fibroin to temperature and solvent concentration during degumming. However, there is no comprehensive information on the influence of these processing parameters on fluorescence evolution and decay during fluorescent silk processing. Therefore, we conducted a spectroscopic study on fluorescence decay as a function of temperature, concentration, and duration for fluorescent silk cocoon degumming. Sodium carbonate solution was tested for degumming the fluorescent silk cocoons with different concentrations and temperatures; also, sodium carbonate solution is combined with Alcalase enzyme and triton x-100 to find optimal degumming conditions. Additionally, we conducted a molecular dynamics study to investigate the fundamental effect of temperature on the stability of the fluorescent protein. We observed degumming temperature as the prime source of fluorescent intensity reduction. From the MD study, fluorescence degradation originated from the thermal agitation of fluorescent protein Cα atoms and fluctuations of amino acid residues located in the chromophore region. Overall, degumming fluorescent silk with sodium carbonate and Alcalase enzyme solution at 25 ℃ preserved fluorescence.

• Composites Research
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• 제35권6호
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• pp.412-418
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• 2022

메타크릴산과의 에스터화 반응을 통해 브롬화 에폭시 수지와 일반 에폭시 수지의 혼합물로부터 난연성 비닐에스터 핫멜트 필름을 제조하였고 이를 이용하여 탄소섬유와 비닐에스터 복합 프리프레그를 제조하였다. 저점도 비스페놀-A와 고점도 브롬화 비스페놀-A 에폭시 전구체를 혼합하여 필름 생산에 적합한 VE 수지의 점도를 최적화하였다. 경화된 VE 수지의 브롬 함량 증가는 비 브롬화 VE에 비해 제한 산소 지수(LOI)(39%), 25℃에서의 저장 탄성률(2.4 GPa) 및 잔류 탄화물(16.1%) 값을 더 증가시켰다. 합성한 VE 프리프레그의 수동 레이업과 후속 경화로 인장 및 굴곡 강도가 우수한 CF 강화 복합재를 성공적으로 제작하였다. 본 연구 결과는 스티렌이 없는 친환경적인 VE 복합 재료 공정의 향후 산업화에 대한 높은 가능성을 보여준다.