• 한국식품저장유통학회지
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• 제30권5호
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• pp.785-796
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• 2023

The aim of this study was to elucidate chemical structures and rheological properties of arabinogalactans (AGs) isolated from three legumes including black gram (BG), great northern bean (GNB), and California small white bean (CSWB). The ratio of galactose to arabinose (G/A) in three legumes increased in the order of BG > GNB > CSWB. The rheological measurements of 1-5% (w/v) AG solutions revealed Newtonian and non-Newtonian flow behaviors. BG exhibited yield stress, indicating plastic behavior. Small-amplitude oscillatory tests indicated viscoelastic properties of BG, GNB, and CSWB ranging from solid-like, paste-like, and liquid-like behaviors, respectively. Small-strain oscillatory tests were conducted to assess the structure recovery of the AGs after pre-shearing. G" values of BG and GNB increased, but those of CSWB remained constant after shearing. These results suggest that the chemical structures of the AGs, particularly their G/A ratios, influence their rheological properties.

• Korea-Australia Rheology Journal
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• 제16권3호
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• pp.135-140
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• 2004

Morphological and rheological properties of the poly(methyl methacrylate) (PMMA) and polystyrene (PS) blends were studied by scanning electron microscopy (SEM) and advanced rheometric expansion system (ARES). From the SEM results, the PMMA-PS blends showed dispersed morphology and the particle size of the dispersed phase was quite small (0.1~0.6 $\mu\textrm{m}$ compared with other immiscible polymer blends. Values of the interfacial tension of the PMMA-PS blend were obtained from the Choi-Schowalter and the Palierne emulsion models using the storage modulus of the PMMA and PS, and found to be 1.0 and 2.0 mN/m, respectively. The interfacial tension between the PMMA and PS was also calculated from the Flory-Huggins polymer-polymer interaction parameter ($\chi$) and found to be from 0.98 to 1.86 mN/m depending on the molecular weight and composition. Comparing the values of the interfacial tension from the Flory-Huggins polymer-polymer interaction parameter and the values measured by oscillatory rheometer, it is suggested that the interfacial tension of the PMMA-PS blend obtained from the polymer-polymer interaction parameter are in good agreement with the values obtained by rheological measurements.

• Macromolecular Research
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• 제15권4호
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• pp.291-301
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• 2007

The rheological behaviors and morphologies of polylactide (PLA) and chemically modified plasticized starch (CMPS) blends were investigated. For this study, oscillatory shear flow measurements of the PLA, CMPS and their blends were performed. A scanning electron microscope (SEM) study was also conducted on the extracted extrudates of the blends. The morphology of the blend changed in relation to the composition: sphere-shaped CMPS disperse/continuous PLA, rod-like deformed CMPS phase/continuous PLA, a co-continuous structure with bridged CMPS long rods and PLA dispersed/continuous CMPS. The composition of the phase inversion could be estimated and closely coincided from the observed morphology experimental results. The rheological behavior of the blends, from oscillatory measurements, was found to vary in relation to the composition, and reflected the morphologies of the blends. PLA showed Newtonian flow behavior, while CMPS showed strong shear thinning behavior. The relationships between the morphology and rheological properties were observed in detail.

• Food Science and Biotechnology
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• 제16권4호
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• pp.610-614
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• 2007

Dynamic rheological properties of honeys with invert sugar at different mixing ratios of honey and invert sugar (10/0, 812, and 6/4 ratios) were evaluated at various low temperatures (-15, -10, -5, and $0^{\circ}C$) using a controlled stress rheometer for small-deformation oscillatory measurements. Honey-invert sugar mixtures displayed a liquid-like behavior, with loss modulus (G") predominating over storage modulus (G') (G">>G'), showing the high dependence on frequency (${\omega}$). The magnitudes of G' and G" increased with a decrease in temperature while their predominant increases were noticed at -10 and $-15^{\circ}C$. The greater tan ${\delta}$ values were found at higher temperature and ratio of honey to invert sugar, indicating that the honey samples at subzero temperatures become more viscous with increased ratio of honey to invert sugar and temperature. The time-temperature superposition (TTS) principle was used to bring G" values at various temperatures together into a single master curve. The TTS principle was suitable for the honey samples in the liquid-like state. The progress of viscous property (G") was also described well by the Arrhenius equation with high determination coefficients ($R^2=0.99$). Dynamic rheological properties of honey samples seem to be greatly influenced by the addition of invert sugar.

• Journal of Magnetics
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• 제21권2호
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• pp.261-265
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• 2016

Surface tension is a major factor in the thermodynamics as well as fluid properties of Magneto-Rheological Fluids (MRF). We measured the surface tension of an MRF using two different methods. A wettability characterization based on contact angles measurements for the fluid interacting with two different surfaces was conducted. A hydrocarbon based commercial MRF with more than 80% solid weight, placed on quartz and poly-tetra-fluoroethylene (PTFE) surfaces was used. We measured the fluids' surface tension value by means of contact angles measurements and by the falling drop method.

• Korea-Australia Rheology Journal
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• 제17권4호
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• pp.191-198
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• 2005

The static and dynamic rheological behavior of concentrated sodium dodecylsulfate (SDS) stabilized, deformability controllable polydimethylsiloxane (PDMS) emulsions is reported and comparisons made with silica (hard sphere) suspensions. Steady-mode measurements indicate 'hard' (viscoelastic) droplets behave as hard spheres, while 'soft' (viscous) droplets induce structural flexibility of the emulsion against shear. Dynamic-mode measurements reveal that viscoelasticity of droplets provides the great magnitude of elasticity for the 'hard' emulsion, while formation of planar films between droplets is the origin of the elasticity of 'soft' emulsions. Combination of steady and dynamic rheological behavior has enabled depiction of droplet structure evolution in relation to the shear stress applied, especially by taking advantage of the normal force that reflects the transient deformation of droplets.

• Journal of Dairy Science and Biotechnology
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• 제36권3호
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• pp.186-186
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• 2018

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.169-173
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• 2004

The control of the rheological properties of a fluid during processing is important and can determine the efficiency of the production in addition to the performance of the final product. The vast majority of process fluids are viscoelastic, hence an instrument that measures both the viscous and elastic properties of the material during processing would be of great practical use. However, most in-line instruments commercially available to date are only capable of measuring viscosity at a single shear rate. An in-line rheometer that measures both the viscous and elastic properties of fluids over a wide range of shear rates simultaneously has been described in a previous publication (Glasscock et at., 2003) in which the results of measurements on flowing sunflower oil were presented. Before this instrument can be used in an industrial situation, it must be demonstrated that the generated results are the same as, or bear some fixed relationship to, the results obtained by conventional off-line rheometers. To this end, the present investigation describes the measurements of a standard reference fluid, polyisobutylene dissolved in 2,6,10,14-tetramethylpentadecane, labelled SRM2490 by the National Institute of Standards and Technology (NIST) in the USA. The results obtained using the in-line rheometer show remarkably good correlation for viscosity, using a modified Cox­Merz rule, with the results supplied with the reference material from NIST.

• International Journal of Industrial Entomology and Biomaterials
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• 제27권1호
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• pp.180-184
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• 2013

Recently, silk sericin has attracted the attention of researchers owing to its useful properties as a biomaterial including 1) good wound healing and cell activities, 2) fast gelation character, and 3) high water retention property. In the present study, silk sericin was prepared using different extraction times in hot water and the effect of extraction time on the rheological properties of sericin solutions and gels was examined. It was found that the production yield of sericin increased with extraction time. The shear viscosity of sericin solutions and gels decreased with increasing extraction time due to a decrease in sericin molecular weight. When the sericin solution transformed to a gel, the viscosity increased and the shear thinning behavior was more evident. In addition, the shear stress measurements indicated that the slip between the sericin samples and the measuring plate of the rheometer was increased by the gelation of sericin. The compression strength of sericin gel could be increased remarkably (by more than 100 fold) by preparation using the freezing and thawing method.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.364-364
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• 2006

The rheological properties of Parmax 1200, a new semi-flexible substituted polyphenylene, were investigated. The reported high stiffness of the material was confirmed. The rheological measurements proved that, despite the very high stiffness of the molecules, Parmax showed shear thinning and that, although the viscosity is very high and the melt is highly elastic, the polymer can be extruded in the melt. A worm-like morphology was detected in AFM and TEM. This morphology could explain the reported mechanical and rheological behaviour. The compatibility with flexible chain polymers (e.g. polycarbonate) could also be explained by the worm-like morphology.