• Applied Chemistry for Engineering
• /
• v.25 no.2
• /
• pp.209-214
• /
• 2014

In this paper, the rheological behaviors and non-Newtonian characteristics of maltenes which is effected by hydrocarbon solvent type, solvent mixing ratio, temperature and shear rate was measured and compared with oil sands bitumen. Maltenes was made by SDA (solvent deasphalting) method from oil sands bitumen. Oil sands bitumen had apparent viscosities of $800{\sim}150000mPa{\cdot}s$ measured at a shear rate of $50sec^{-1}$ in the range of $25{\sim}85^{\circ}C$ and showed yield stress of 0.1~0.3 Pa at the temperatures below $35^{\circ}C$. All the oil sands bitumen and maltenes exhibited a shear-thinning, i.e. pseudoplastic behavior and apparent viscosity of maltenes decreased with decreasing carbon numbers of hydrocarbon solvent. The change in apparent viscosity with temperature could be described by the simple Guzman-Andrade equation, and maltene viscosities were decreased as the mixing ratio of n-pentane was raised. Also, all maltenes approached to Newtonian fluid as temperature were increased. the degree of pseudoplasticity was enhanced with decreasing carbon number of solvent.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.46 no.5
• /
• pp.608-615
• /
• 2017

The objective of this study was to evaluate the physicochemical, structural, and rheological properties of new domestic potato cultivars ('Goun', 'Sebong', and 'Jinsun') against the foreign potato cultivar 'Atlantic'. Based on the results obtained from scanning electron micrograph, X-ray, and Fourier transform infrared spectrum analyses, the structural properties of all potato flours were not considerably different. Rapid visco analyzer analyses showed that the setback viscosities of 'Goun', 'Sebong', and 'Jinsun' were significantly lower than that of 'Atlantic'. For steady shear rheological properties, potato flour dispersions showed shear-thinning behaviors (n=0.45~0.49) at $25^{\circ}C$. Apparent viscosity and consistency index of 'Atlantic' were similar to those of 'Sebong' and 'Jinsun'. For dynamic shear rheological properties, storage modulus (G′) and loss modulus increased, whereas complex viscosity (${\eta}^*$) was reduced with increasing frequency from 0.63 to 62.8 rad/s. G′ and ${\eta}^*$ values of 'Jinsun' were significantly higher than those of the other potato cultivars.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.6
• /
• pp.21-26
• /
• 2018

Thermoplastic starch (TPS) was prepared by mixing starch with glycerol as a plasticizer. The glycerol content ranged from 20 to 35 wt. % and TPS was prepared in a twin screw extruder. The shear viscosity, thermal and mechanical properties of the TPS were investigated. The viscosity of TPS exhibited typical shear thinning behavior: decreasing viscosity with increasing shear rate. The power index, n, increased with increasing glycerol content. This is because as the content of glycerol, a Newtonian fluid, increases, the viscosity behavior of the TPS becomes closer to that of a Newtonian fluid. The thermal behavior of TPS showed that starch and glycerol are miscible. In addition, when TPS was aged for more than one day at room temperature, TPS showed a partially miscible phase structure. The moisture absorbed into the TPS was assumed to change the phase behavior. The mechanical properties of TPS were found to be strongly dependent on the content of the plasticizer. Both the toughness and stiffness increased with increasing plasticizer content. DSC showed that this unusual result was due to the combined effect of humidity and the high amylose content in starch.

• Korea-Australia Rheology Journal
• /
• v.20 no.2
• /
• pp.59-63
• /
• 2008

A theoretical model was developed to describe the flow behavior of a filled polymer in the packing stage of reaction injection molding and predict the residual stress distribution of thin injection-molded parts. The model predictions were compared with experiments performed for phenol-formaldehyde resin filled with wood dust and cured by urotropine. The packing stage of reaction injection molding process presents a typical example of complex non-isothermal flow combined with chemical reaction. It is shown that the time evolution of pressure distribution along the mold cavity that determines the residual stress in the final product can be described by a single 1D partial differential equation (PDE) if the rheological behavior of reacting liquid is simplistically described by the power-law approach with some approximations made for describing cure reaction and non-isothermality. In the formulation, the dimensionless time variable is defined in such a way that it includes all necessary information on the cure reaction history. Employing the routine separation of variables made possible to obtain the analytical solution for the nonlinear PDE under specific initial condition. It is shown that direct numerical solution of the PDE exactly coincides with the analytical solution. With the use of the power-law approximation that describes highly shear thinning behavior, the theoretical calculations significantly deviate from the experimental data. Bearing in mind that in the packing stage the flow is extremely slow, we employed in our theory the Newtonian law for flow of reacting liquid and described well enough the experimental data on evolution of pressure.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2001.11a
• /
• pp.53-53
• /
• 2001

종이의 전기적 성질 가운데 유전율은 전기장에 대한 종이의 물리화학적인 반응으로 일반적으로 종이의 밀도와 종이를 구성하는 성분의 쌍극자 모멘트에 비례하며 온도에 따라서도 변화한다. 일반적으로 온도가 상승하면 열에너지를 얻게된 쌍극자가 전기장에 배열됨으로써 유전율이 상승하지만 온도가 유리전이점 이상으로 높아질 경우에는 열적 교란에 의해서 분극능력이 감소하게 되어 유전완화 현상이 나타난다. 전기절연지로 사 용될 종이의 절연특성을 이해하기 위해서는 사용환경에 따른 유전적 특성 및 tan 0에 관한 연구가 필요하며 필름형성능력이 우수한 polyvinyl a1cohoHPV A)와 acrylonitrile을 이용하여 시아노에틸화한 PYA의 표면처리에 의해 종이의 유전적 특성이 향상되었음을 기존의 연구를 통하여 확인할 수 있었다. 본 연구에서는 전기절연지가 사용되는 환경조건에서 PYA를 기본물질로하는 유전필름 의 열적 안정성을 평가하였으며, 아울러 표면사이징 공정에서의 적용성 검토를 위하여 용액의 유동특성을 분석하였다. 유전특성 향상을 위해서는 표면 사이즈제의 유도체화 과정에서 쌍극자 모벤트의 밀도 증가를 통한 유전율 향상이 요청되며 이와 동시에 네트원 구조를 통하여 전기장에 대 한 물리적 특성이 유지되어야 한다. 본 연구에서는 W AXD( wide angle x-ray diffraction)를 이용하여 시아노에틸화 반응 과 고온에서의 열화에 의한 필름의 결정화도를 평가하였으며 온도 상승에 따른 흡열 피크의 변화를 통하여 온도 변화에 따른 PYA 분자구조의 변화와 유리전이온도의 추이 를 분석하였다. 또 열화과정에서 수반되는 필름의 중량감소율을 평가함으로써 열안정성 을 평가하였다. 그 결과 시아노에틸화한 PYA가 안정된 분자구조를 유지하고 있음을 확인할 수 있었다. 시아노에틸화한 PYA용액의 점탄성 평가를 위하여 storage modulus와 loss modulus 를 분석하였다. 일반적 유변특성 평가 결과 PYA용액은 shear-thinning, pseudoplastic 한 특성을 나타내어 표면사이즈 공정에서의 적용 가능성을 확인할 수 있었다.

• Food Science of Animal Resources
• /
• v.35 no.2
• /
• pp.156-163
• /
• 2015

The effects of low molecular-weight collagen peptides derived from porcine skin were investigated on the physicochemical and sensorial properties of chocolate ice cream. Collagen peptides less than 1 kDa in weight were obtained by sub-critical water hydrolysis at a temperature of $300^{\circ}C$ and a pressure of 80 bar. Ice cream was then prepared with gelatin powder and porcine skin hydrolysate (PSH) stabilizers mixed at seven different ratios (for a total of 0.5 wt%). There was no significant difference in color between the resulting ice cream mixtures. The increase in apparent viscosity and shear thinning of the ice cream was more moderate with PSH added than with gelatin. Moreover, the samples containing more than 0.2 wt% PSH had enhanced melting resistance, while the mixture with 0.2 wt% PSH had the lowest storage modulus at $-20^{\circ}C$ and the second highest loss modulus at 10℃, indicating that this combination of hydrocolloids leads to relatively softer and creamier chocolate ice cream. Among the seven types of ice creams tested, the mixture with 0.2 wt% PSH and 0.3 wt% gelatin had the best physicochemical properties. However, in sensory evaluations, the samples containing PSH had lower chocolate flavor scores and higher off-flavor scores than the sample prepared with just 0.5 wt% gelatin due to the strong off-flavor of PSH.

• Food Science of Animal Resources
• /
• v.38 no.5
• /
• pp.995-1007
• /
• 2018

Changes in the physicochemical properties of ready-to-feed liquid infant formula (LIF) stored at different temperatures (10, 20, 30, and $40^{\circ}C$) for 6 mon, focusing on 5-hydroxymethylfurfural (HMF) content, color, pH, fat globule size distribution, and rheological properties were determined. The HMF content increased with storage time, and LIF stored at $40^{\circ}C$ had a higher HMF content than that of LIF stored at $10^{\circ}C$. The lightness ($L^*$) decreased while redness ($a^*$) and yellowness ($b^*$) increased with increasing HMF content. The fat globule size and pH of LIF stored at $10^{\circ}C$ did not change. However, in the case of LIF stored at $30^{\circ}C$ and $40^{\circ}C$, the fat globule size increased and the pH decreased during storage for 6 mon. LIF stored at $40^{\circ}C$ had a higher apparent viscosity (${\eta}_{a,10}$) than that of LIF stored at $10^{\circ}C$, and the shear-thinning behavior of LIF stored at higher temperature was stronger than that of LIF stored at low temperature. The physicochemical changes of LIF during storage were accelerated by Maillard reaction (MR) at higher storage temperatures. Therefore, even if LIF is aseptically manufactured, we recommend that sterilized LIF should be stored at low temperature in order to minimize quality changes during storage.

• Macromolecular Research
• /
• v.11 no.6
• /
• pp.410-417
• /
• 2003

Poly(methyl methacrylate-co-acrylonitrile) [P(MMA-co-AN)]/Na-MMT nanocomposites were synthesized through emulsion polymerization with pristine Na-MMT. The nanocomposites were exfoliated up to 20 wt% content of pristine Na-MMT relative to the amount of MMA and AN, and exhibited enhanced storage moduli, E', relative to the neat copolymer. The exfoliated morphology of the nanocomposite was confirmed by XRD and TEM. 2-Acryla-mido-2-methyl-1-propane sulfonic acid (AMPS) widened the galleries between the clay layers before polymerization and facilitated the comonomers, penetration into the clay to create the exfoliated nanocomposites. The onset of the thermal decomposition of the nanocomposites shifted to a higher temperature as the clay content increased. By calculating areas of tan$\delta$ of the nanocomposites, we observed that the nanocomposites show more solid-like behavior as the clay content increases. The dynamic storage modulus and complex viscosity increased with clay content. The complex viscosity showed shear-thinning behavior as the clay content increased. The Young's moduli of the nano-composites are higher than that of the neat copolymer and they increase steadily as the silicate content increases, as a result of the exfoliated structure at high clay content.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.4
• /
• pp.844-851
• /
• 2010

Controlling the dissolved oxygen (DO) in the fed-batch culture of the medicinal mushroom Ganoderma lucidum led to a 2-fold increase of the maximum biomass productivity compared with uncontrolled DO conditions. By contrast, extracellular polysaccharide (EPS) production was two times higher under oxygen limitation (uncontrolled DO) than under increased oxygen availability (controlled DO). Morphologically, dispersed mycelium was predominant under controlled DO conditions, with highly branched hyphae, consistent with the enhanced culture growth noted under these conditions, whereas in the uncontrolled DO process mycelial clumps were the most common morphology throughout the culture. However, in both cultures, clamp connections were found. This is an exciting new finding, which widens the applicability of this basidiomycete in submerged fermentation. In rheological terms, broths demonstrated shear-thinning behavior with a yield stress under both DO conditions. The flow curves were best described by the Herschel-Bulkley model: flow index down to 0.6 and consistency coefficient up to 0.2 and 0.6 Pa $s^n$ in uncontrolled and controlled cultures DO, respectively. The pseudoplastic behavior was entirely due to the fungal biomass, and not to the presence of EPS (rheological analysis of the filtered broth showed Newtonian behavior). It is clear from this study that dissolved oxygen tension is a critical process parameter that distinctly influences G. lucidum morphology and rheology, affecting the overall performance of the process. This study contributes to an improved understanding of the process physiology of submerged fermentation of G. lucidum.

• Journal of Microbiology and Biotechnology
• /
• v.22 no.11
• /
• pp.1494-1500
• /
• 2012

Fermentation with filamentous fungi in a bioreactor is a complex dynamic process that is affected by flow conditions and the evolution of the rheological properties of the medium. These properties are mainly affected by the biomass concentration and the morphology of the fungus. In this work, the rheological properties of a fermentation with the fungus Beauveria bassiana under different hydrodynamic conditions were studied and the rheological behavior of this broth was simulated through a mixture of carboxymethyl cellulose sodium and cellulose fibers (CMCNa-SF). The bioreactor was a 10 L CSTR tank operated at different stir velocities. Rheological results were similar at 100 and 300 rpm for both systems. However, there was a significant increase in the viscosity accompanied by a change in the consistence index, calculated according to the power law model, for both systems at 800 rpm. The systems exhibited shear-thinning behavior at all stir velocities, which was determined with the power law model. The mixing time was observed to increase as the cellulose content in the system increased and, consequently, the efficiency of mixing diminished. These results are thought to be due to the rheological and morphological similarities of the two fungal systems. These results will help in the optimization of scale-up production of these fungi.