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Rheological and Physical Properties of Sulfonated Polystyrene Ionomer Solutions and the Membranes
채동욱,최경락,김병철,Chae, Dong Wook,Choi, Kyung Rak,Kim, Byoung Chul The Korean Fiber Society 2018 한국섬유공학회지 Vol.55 No.1
The rheological properties of sulfonated polystyrene (SPS) ionomer solutions were found to be significantly affected by solvent polarity, counterion, sulfonation level, and temperature. In the dilute concentration regime, the reduced viscosity (${\eta}_{red}$) of SPS solutions in the dimethyl sulfoxide (DMSO), which is a polar solvent, increased with decreasing concentration, whereas opposite effects were observed in low-polarity solvent tetrahydrofuran (THF). H-SPS solutions in THF showed typical shear-thinning behavior over all the measured frequencies, while solutions in DMSO showed shear-thickening behavior at low shear rates, followed by shear-thinning behavior at higher shear rates. These different behaviors might result from differences in polymer-solvent interactions and the chain conformation. SPS solutions in DMSO containing monovalent ions ($Na^+$) exhibited higher dynamic viscosity values than those with divalent ions ($Ca^{2+}$, $Mg^{2+}$) because of the different degrees of chain expansion. In DMSO, the dynamic viscosity increased with temperature, regardless of the sulfonation level and counterion. Both the proton conductivity and methanol permeability of the SPS membranes increased with increasing sulfonation level and exhibited an abrupt increase between 10 and 15 mol%, indicative of a percolation threshold.
채동욱,최경락,김병철,Chae, Dong Wook,Choi, Kyung Rak,Kim, Byoung Chul The Korean Fiber Society 2017 한국섬유공학회지 Vol.54 No.3
Poly(ethylene terephthalate) (PET) and poly(trimethylene terephthalate) (PTT) were melt blended at $280^{\circ}C$ at varying blending time and ratio. The resulting physical properties were examined in relation to ester exchange reactions. The PET/PTT 50/50 blends (by weight percentage) exhibited double melting peaks ($T_m$) up to 30 min blending time beyond which they were merged to one broader peak. The melting peak had a nearly linear relationship with blending time and displayed a much steeper decrease for ET units than for TT units. Two new peaks for asymmetric aromatic carbons were detected in $^{13}C$-NMR spectra and their intensity increased notably from 40 min blending time which was consistent with thermal analysis. The dissolution of copolyesters occurred even after 10 min blending time and its degree increased with blending time. FESEM images of chloroform etched fracture surfaces displayed coarse and continuous phase properties from 40 min blending time while losing the spherical shape of each component. In the DSC measurement of the PET/PTT blends prepared at various ratios at a given blending time of 20 min, all the blends exhibited a single glass transition temperature ($T_g$) more consistent with the Gordon-Taylor equation than the Fox equation. In addition, a single $T_m$ peak was observed in each sample, except for 50/50 composition, which shows the coexistence of $T_m$ for each component. All blends except for 50/50 exhibited a similar WAXD patterns to their rich component. This was evidenced by solubility test results showing the highest solubility for 50/50 blends. This phenomenon was also confirmed in FESEM measurement of chloroform etched fracture surfaces where the blends composed of an equal amount of the component exhibited coarse and dumbbell-like domains.
유황시비처리가 열무의 Quinone Reductase 유도물질 생성에 미치는 영향
김경아(Kyung-A Kim),노치웅(Chi-Woong Rho),최경락(Kyung-Rak Choi),황해준(Hae-Jun Hwang),최혜선(Hye-Seon Choi) 한국식품영양과학회 2004 한국식품영양과학회지 Vol.33 No.6
본 연구는 열무에서 다른 십자화과 식물에서 발견되는 sulforaphane 유사물질의 분획과 quinone reductase inducing activity를 측정하였고 열무생육시 유황을 첨가해 주면 이러한 활성이 현저히 증가되는 것을 보았다. Sulforaphane 유사 물질의 분획은 유황을 토양에 1,818 g/㎥ 첨가시 가장 높았고, 열무의 생산성을 고려하여 토양을 석회로 중화시켰을 때 감소되었다. 유황을 처리하여 키운 열무에 생리활성성분을 가진 유황화합물이 증가되므로 이러한 열무는 생체에 섭취시 detoxification enzyme을 유도하여 암발생을 지연시키거나 낮출 수 있는 chemoprevention의 효율이 기대된다. Young radishes which were grown in the soil containing sulfur increased quinine reductase (QR) activity in Hepa 1c1c cells and isothiocyanate-like compound analyzed by HPLC. QR inducing activity was maximum in young radishes grown with 1,818 g/㎥ sulfur and was decreased when the soil was neutralized with lime mortar in order to improve a recovery. These results have suggested that consumption of young radishes, especially grown in the presence of sulfur, would prevent from cancer incidence through inducing detoxification enzymes and could have therapeutic effects for chemoprevention.