• Korea-Australia Rheology Journal
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• v.15 no.2
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• pp.55-61
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• 2003

The steady shear flow properties of vaseline generally used as a base of the pharmaceutical dosage forms were studied in the consideration of wall slip phenomenon. The purpose of this study was to show that how slip may affect the experimental steady-state flow curves of semisolid ointment bases and to discuss the ways to eliminate (or minimize) wall slip effect in a rotational rheometer. Using both a strain-controlled ARES rheometer and a stress-controlled AR1000 rheometer, the steady shear flow behavior was investigated with various experimental conditions ; the surface roughness, sample preparation, plate diameter, gap size, shearing time, and loading methods were varied. A stress-controlled rheometer was suitable for investigating the flow behavior of semisolid ointment bases which show severe wall slip effects. In the conditions of parallel plates attached with sand paper, treated sample, smaller diameter fixture, larger gap size, shorter shearing time, and normal force control loading method, the wall slip effects could be minimized. A critical shear stress for the onset of slip was extended to above 10,000 dyne/$\textrm{cm}^2$. The wall slip effects could not be perfectly eliminated by any experimental conditions. However, the slip was delayed to higher value of shear stress by selecting proper fixture properties and experimental conditions.

• Structural Engineering and Mechanics
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• v.51 no.1
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• pp.1-13
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• 2014

This paper reports an experimental study into the rheological behaviour of self consolidating concrete (SCC). The investigation aimed at quantifying the impact of the varying amounts of mineral admixtures on the rheology of SCC containing natural sand. Apart from the ordinary Portland cement (OPC), the cementitious materials such as fly ash (FA), ground granulated blast furnace slag (GGBS) and micro-silica (MS) in conjunction with the mineral admixtures were used in different percentages keeping the mix paste volume and flow of concrete constant at higher atmospheric tempterature ($30^{\circ}$ to $40^{\circ}C$). The rheological properties of SCC were investigated using an ICAR rheometer with a four-blade vane. The rheological properties of self-consolidating concrete (SCC) containing different mineral admixtures (MA) were investigated using an ICAR rheometer. The mineral admixtures were fly ash (FA), ground granulated blast furnace slag (GGBS), and micro silica (MS). The results obtained using traditional workability results are compared with those obtained using ICAR rheometer. The instrument ICAR (International Center for Aggregate Research) rheometer employed in the present study for evaluating the rhelogical behaviour of the SCC is found to detect systematic changes in workability, cementitious materials, successfully. It can be concluded that the rheology and the slump flow tests can be concurrently used for predicting the flow behaviours of SCC made with different cementitious materials.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.231-235
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• 2012

Plasticity is the ability of clay to respond to pressure with a continuous and permanent change of shape in any direction without breaking apart, and hold that shape when released. In this work, the effect of water content and aging period on the plasticity of porcelain clay was evaluated using the capillary rheometer to measure the flow rate and the shear stress. The shear stress of porcelain clay was slightly increased with increasing the aging period, indicating that the plasticity of porcelain clay was influenced by an organic content. It was also observed that the water content in the porcelain clay had a great influence on the plasticity of porcelain clay. The shear stress with water content of 21 wt% was sharply increased with increasing shear rate, but the shear stresses with water contents of 24 and 27 wt% is gently incremented.

• KCI Concrete Journal
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• v.13 no.1
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• pp.35-41
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• 2001

This paper investigated rheological properties of binder pastes for self-compacting high performance concrete. Six mixtures of self-compacting concrete were initially prepared and tested to estimate self-compacting property. Then, the binder pastes used in self-compacting concrete were tested for rheological properties using a rotary type rheometer. Binder pastes with different water-binder ratios arid flow values were also examined to evaluate their rheological characteristics. The binders were composed of ordinary Portland cement, fly ash, two types of pulverized blast-furnace slag, and limestone powder. The flow curves of binder pastes were obtained by a rotary type rheometer with shear rate control. Slump flow, O-funnel time, box, and L-flow teats were carried out to estimate self-compacting property of concrete. The flow curves of binder pastes for self-compacting concrete had negligible yield stresses and showed an approximately linear behavior at higher shear rates beyond a certain limit. Test results also indicated that the binders incorporating fly ash are more appropriate than the other types of binders in quality control of self-compacting concrete.

• Korea Journal of Cosmetic Science
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• v.2 no.1
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• pp.33-46
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• 2020

Cosmetics are representative complex fluids, and there have been many studies focusing on the correlation between the rheological properties and sensory attributes. Various instrumental measurements have been suggested to evaluate the sensory attributes, and one of the most common instruments is Texture Analyzer (TA). Although it is reported that the adhesiveness measured by TA is related to the stickiness of cosmetics, there exists reproducibility problem because measurements with TA are sensitive to application conditions. In this study, an instrumental protocol using rotational rheometer has been set up to measure the stickiness of cosmetics. This protocol consists of two steps. The first step is a preconditioning step, and various types of shear deformations are applied to the samples. The next step is the extensional flow and the axial force is measured. When the amplitude of the shear flow corresponded to the linear viscoelastic region, the axial force is the same as those without preconditioning. On the other hand, an axial force decreases as variation nonlinearity increases. It is because the effects of microstructure changes caused by nonlinear deformation affects the extensional flow. It is worth noting that a new protocol facilitates to evaluate the stickiness of cosmetics in a more systematic way.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.75-80
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• 2007

The slotted plate technique has previously been shown to be a successful method for directly measuring the static yield stress of suspensions. In this study, we further establish the usefulness of the slotted plate device as a rheometer especially at low shear rates, taking advantage of the extremely low speeds of the slotted plate technique. Newtonian fluids, a shear thinning fluid, and yield stress fluids were tested using the slotted plate device and the results were compared with those from a commercial rheometer using different standard flow geometries. The relationship between the stress on the plate and the viscosity for the slotted plate device obtained by dimensional analysis (drag) predicts a linear relationship between the force at the plate and the plate speed, consistent with the experimental data. The slotted plate device can measure viscosities at very low shear rates. The apparent viscosity - shear-rate data obtained from the slotted plate device are complementary to those obtained using a commercial rheometer. That is : the slotted plate can measure viscosity in the shear rate range $10^{-7}<\dot{\gamma}<10^{-3}\;s^{-1}$, while the commercial rheometer measures viscosity at shear rates higher than $10^{-3}\;s^{-1}$.

• Preventive Nutrition and Food Science
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• v.19 no.3
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• pp.242-245
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• 2014

The flow behaviors of three thickened fruit juices (orange, apple, and grape juice) prepared with a commercial instant xanthan gum (XG)-based thickener that is marketed in Korea were investigated at different thickener concentrations (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) and setting times (5 and 30 min) using a rheometer and a line-spread measurement method. The flow distance values measured by the line-spread test (LST) were compared with the apparent viscosity (${\eta}_{a,50}$) values measured with a sophisticated computer-controlled rheometer. The ${\eta}_{a,50}$ values of the juices increased as thickener concentration increased, whereas their flow distances decreased. The ${\eta}_{a,50}$ values at the 30-min setting time were much higher than those at the 5-min setting time, indicating that the setting time before serving or consuming thickened juices can affect viscosity values. Plots comparing ${\eta}_{a,50}$ values to LST flow distances revealed strong exponential relationships between the two measures ($R^2$=0.989 and $R^2$=0.987 for the 5- and 30-min setting times, respectively). These results indicate that the LST can be a suitable instrument for evaluating the viscosity of thickened fruit juices prepared with different XG-based thickener concentrations and setting times for the dysphagia diet.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.165.1-165
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• 2001

• The Korean Journal of Food And Nutrition
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• v.32 no.4
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• pp.304-311
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• 2019

Ohmic heating is a heating method based on the principle when an electrical current passes through food. Since this method is internal, electrical current damage occurred during heating treatment. The results of ohmic heated starch's external structure, X-ray diffraction, DSC analysis and RVA were differed from those of conventional heating at the same temperature. Several starches changed more rigid by structure re-aggregation. This change in starch was caused by change of physical, chemical, rheological property. The rheology of ohmic heated potato and corn starch of different heated methods were compared with chemically modified starch. After gelatinization, sample starch suspension (2%, 3%) measured flow curves by rheometer. Cross-linked chemically modified starch's shear stress was decreased with degree of substitution reversibly. Ohmic heated more dramatic, at $60^{\circ}C$. Potato starch's shear stress was less than commercial high cross-linked modified starch. Flow curves of potato starches measured at $4^{\circ}C$, $10^{\circ}C$, $20^{\circ}C$. Showed that Ohmic heated potato starch's shear stress ranging between $4^{\circ}C$ and $20^{\circ}C$ was narrower than modified starch. According to this study, ohmic heated potato starch can be used by decreasing viscosity agent like cross-linked modified starch.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.540-548
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• 2016

The non-Newtonian flow curves of sodium bis-(2-ethylhexyl)sulfosuccinate-water lamellar liquid crystals were obtained in various concentrations and temperatures by using a cone-plate rheometer. By applying non-Newtonian flow equation to the flow curves for AOT-water lamellar liquid crystal samples, the rheological parameters were obtained. Particular attention is given to the hysteresis loop detected when the liquid crystal samples are shear under increasing-decreasing shear stress modes which result in thixotropic and dilatant behavior. Sodium bis-(2-ethylhexyl)sulfosuccinate-water lamellar liquid crystals behave as weak gels when they are subjected to shear flow, but when the applied stress surpasses the yield stress, they exhibit non-linear viscoelasticity. Upon decreasing shear rate, the dispersion still preserves much of its structure and consequently its shear stress remains higher than the values measured in the increasing shear rate mode.