• 한국응용과학기술학회지
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• 제24권2호
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• pp.160-166
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• 2007

The rheological properties and surface tensions of polymer solutions and polymer-surfactant mixed solutions were investigated. The polymers used in this study were a homopolymer of acrylic acid crosslinked with an allyl ether of pentaerythritol, an allyl ether of sucrose, or an allyl ether of propylene (CARBOMER), acylate/C10-30 alkyl acylate crosspolymer (AAAC), and ammonium acryloydimethyltaurate/VP copolymer (ADTV). A solubilizing agent PEG-40 hydrogenated castor oil (HCO-40) and an emulsifying agent polyoxyethylene (20) sorbitan monostearate (POLYSORBATE 60) made the micelles intervening between AAAC polymers, resulting in the increase of viscosity. However, HCO-40 made this behavior over the wider range of surfactant concentration than POLYSORBATE 60. From the view point of surface tensions in the same range of surfactant concentration, AAAC/HCO-40 solution showed the area of increasing surface tension with surfactant concentration in contrast to the AAAC/POLYSORBATE 60 solution showing no increasing area.

• Macromolecular Research
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• 제14권2호
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• pp.132-139
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• 2006

The dispersion of organoclay in ethylene propylene diene terpolymer (EPDM) matrix was correlated with the rheological and swelling properties of nanocomposites. X-ray diffraction pattern (XRD) and transmission electron microscopic (TEM) analysis exhibited the disordered-intercalated structure of EPDM/organoclay nanocomposite. The extent of the disordered phase increased with increasing organoclay content up to a limiting value of 3 wt% after which equilibrium tended towards intercalation. The dispersion effect of organoclay in EPDM matrix was clarified by the physicochemical properties like rheological response and swelling thermodynamics in toluene. The increase in viscoelastic properties of EPDM nanocomposite with increasing organoclay content up to 3 wt%, followed by a subsequent decrease up to 4 wt%, was correlated in terms of the disordered and ordered states of the dispersed nano-clay sheets. Swelling measurements revealed that the change in entropy of the swelling increased with the increase in disorder level but decreased with the increase in intercalation level of organoclay in the disordered-intercalated nanocomposite. The increase in solvent uptake was comparable with the free volume in EPDM matrix upon inclusion of silicate particles, whereas the inhibition in solvent uptake for higher organoclay loading was described by bridging flocculation.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1987년도 학술발표초록집
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• pp.11-11
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• 1987

Among other poly(4,4'-terephthanilidealkylamide)s (PTAA's), poly (4,4'-terephthanilideadipamide) (PTAd) gave clear critical concentration curves. For PTAA's with methylene units more than 6, the critical concentration (C*) seemed to be beyond the solubility limit of H₂SO₄. Under shearing conditions, the nematic domains were easily oriented and stretched in the direction of shear , and a fibrillar structure resulted. At low frequencies, a monotollous reduction of loss tangent (tan) was observed as concentration increased. At high frequencies, however, tan was increased above C* again, and showed maximum at saturation concentration (Cs). With increasing temperature, viscosity of isotropic and anisotropic phases was normally decreased, while viscosity of biphases was increased. Plot of complex viscosity (If) against temperature based on rheological measurements exhibited a good correlation with phase diagram constructed by polarizing microscope observations. Rheological parameters suggested the optimum dope concentration of PTAd with inherent viscosity 2.02 at 30oc is in the vicinity of 19.2 wt%, which seemed to agree well with spinning experiments (around 19.4 wt%). In general, effects of spinning and annealing conditions on the mechanical properties of PTAA fibres were most pronounced in PTAd fibre spun from anisotropic spinning dope .

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.616-619
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• 2004

This study has focused on the possibility for recycling of tailings from the Sangdong tungsten mine as powder. The experimental tests for entrapped water ratio were carried out in accordance with the specificed method by Okamura. The rheological measurements of cement paste were conducted by using a commerically digital Brookfield viscometer (Model LVDV-II+) equipped with cylindrical spindles. The results of this study, in case of cement paste mixed with tailings, entrapped water ratio was decreased with increasement of mixing ratio. Thickness of pseudo water film was increased, and mean plastic viscosity was decreased with increasing replacement.

• International Journal of Vascular Biomedical Engineering
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• 제4권2호
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• pp.7-12
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• 2006

The present study investigated the effects of the osmotic environment on the rheological properties of erythrocytes and their suspensions. In an iso-osmotic medium, erythrocytes forming a biconcave discocyte under resting conditions, exhibited high deformability. In a low-osmotic medium, the deformability of erythrocytes, which swelled and exhibited a spherical shape, significantly decreased at a high shear stress and the high-shear viscosity of the cell suspension was slightly higher than that of normal blood. Hyper-osmotic stress, however, which caused to form echinocytes, decreased cell deformability but exhibited smaller viscosity in low shear rates than iso-osmotic blood viscosity. These results showed a close relation with the aggregability measurements, in that hypertonic blood showed lower aggregability than the hypotonic and isotonic RBC suspensions. These findings indicate that the physicochemical environment has a strong influence on the rheological properties of the erythrocyte and its suspensions.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1763-1771
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• 2004

An experimental investigation was performed to study the characteristics of ER (Electro-Rheological) fluid flow in a horizontal rectangular tube with or without D. C voltage. To determine some characteristics of the ER flow, 2D PIV(Particle Image Velocimetry) technique was employed for velocity measurements. This research found the mean velocity distributions with 0kV /mm, l.0kV /mm and l.5kV /mm for Re=0, 0.62, 1.29 and 2.26. When the strength of the electric field increased, the cluster of ERF was clearly strong along the test tube and the flow rate decreased. The present results will contribute to the economical and compact design of ER fluids system.

• Korea-Australia Rheology Journal
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• 제19권1호
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• pp.1-5
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• 2007

By combining ultrasonic energy which is essential for the chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends, we were able to modify the molecular structure of polycarbonate (PC) from linear to a branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PC during the course of ultrasound-assisted mixing process. The transformation of molecular structure of PC was confirmed by the measurements of rheological properties of the modified PC. After the ultrasonic irradiation of PC together with MFA, increase in complex viscosities and shear-thinning behavior were observed. The Cole-Cole plot and measurement of extensional viscosities revealed the characteristic features of branched structure with well-defined extensional behavior which is comparable to that of a commercial branched PC.

• 한국세라믹학회지
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• 제28권5호
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• pp.365-372
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• 1991

LAS (lithium aluminosilicate) sol was synthesized using the hydrolysis-condensation reaction of TEOS, chelated Al(OBus)3 and Li-salt with H2O in alcohol (EtOH+2-Propanol) medium. Effects of important reaction parameters on the properties of sol and gel-derived LAS were examined. The crystallization of the sol-gel derived LAS with ${\beta}$-spodumene composition began at ∼600$^{\circ}C$, and a series of polymorphic transformations occurred as temperature was increased to 1100$^{\circ}C$: amorphous LAS\longrightarrowhexagonal LiAl(SiO3)2\longrightarrow${\beta}$-spodumene. Lowering Li content in the gel enhanced densification and retarded the crystallization significantly. Optimum reaction conditions of LAS sol formation for thin coating applications were derived from rheological measurements, and these can be summarized as: H2O/total alkoxides molar ratio=4, pH=∼2.5, and aging time of ∼250h.

• Archives of Pharmacal Research
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• 제8권2호
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• pp.91-98
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• 1985

Dependence of the flow behavior of aqueous suspension of Young-Il bentonite on the concentration and the type of electrolytes was studied. Viscosity measurements were made was Rion Viscotester, using No. 3 rotor at 62.5 R. P. M. at 25.deg.C. As electrolyte concentration increased, the apparent viscosity was observed to increase. Changes in viscosity were in general agreement with predicted results based on the Hofmeister sequence and the Schulze-Hardy rule. The observed electrolyte effect on the apparent viscosity was discussed in terms of the Verwey-Overbeek theory.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.152-157
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• 2002

The cure and rheological behavior of Diglycidyl ether of bisphenol F, catalyzed by four kinds of imidazoles and a Nadic methyl anhydride curing agent were studied using a differential scanning calorimeter (DSC) and rheometer. The isothermal traces were employed to analyze cure reaction. The DGEBF/anhydride conversion profiles showed autocatalyzed reaction characterized by maximum conversion rate at 20~40 % of the reaction. The rate constants obtained from isothermal test showed temperature dependance, but reaction order did not. The order of reaction (m+n) was calculated to be close to 3. The measurements of viscosity and relation time in the presence of inorganic fillers were carried out at different isothermal curing temperatures. The viscosity and gelation time increased with filler content at the same isothermal temperature.