• 한국식품영양과학회지
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• 제28권6호
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• pp.1293-1297
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• 1999

Effect of rice protein and lipid on rheological properties of gelatinized rice flour solutions(4%) with three rice varieties(Dongjin, Jinmi, Tamjin) known for varying taste of cooked rice was investigated with Haake viscometer. The rheological behaviors of all rice flour solutions were illustrated by Herschel Bulkley equation and exhibited pseudoplastic behavior with yield stress. When rice flour solutions treated with protease and dithiothreitol, there was decreased in flow behavior index value. Flow behavior index was decreased by dealbumin and deglutelin rice flour solutions among deprotein groups. The Jinmi rice flour solutions exhibited slightly lower consistency index than Dongjin and Tamjin. Defatted rice flour solutions exhibited lower consistency index than rice flour solutions, while dealbumin, deglutelin rice flour solutions exhibited high consistency index. Protease treated rice flour solutions exhibited increase in Dongjin and Tamjin. The yield stress was increased in sequence eating quality. Yield stress of defatted rice flour solutions was decreased, while deglutelin and rice starch flour solutions was increased. The time dependent charac teristics of all rice flour solutions appeared forming hysteresis loop and thixotropic behavior showed. The time dependent characteristics was appeared in sequence eating quality. Rice starch and deglutelin flour solutions appeared greatly time dependent characteristics, but defatted rice flour solutions appeared very little.

• Korea-Australia Rheology Journal
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• 제17권2호
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• pp.79-85
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• 2005

Aqueous mixtures of hyaluronic acid and poly(vinyl alcohol) system and hydrogels thereof were introduced to obtain new bioartificial materials that have excellent mechanical properties, biocompatibility and enhanced rheological properties. The interactions between hyaluronic acid and poly(vinyl alcohol) and/or borax were investigated by rheological measurements. Preparation parameters of the aqueous mixtures were mixture composition, the degree of hydrolysis of poly(vinyl alcohol) and borax concentration. From the rheological behavior, it could be deduced that the key factor of the interaction between hyaluronic acid and poly(vinyl alcohol) was the hydrogen bonding between them and the effect was pronounced with borax. Enhanced viscosity was observed at the composition of $20wt\%$ of hyaluronic acid solution and $80wt\%$ of poly(vinyl alcohol) and borax solution. Rheological properties were influenced by the degree of hydrolysis of poly(vinyl alcohol) and borax concentration. As the degree of hydrolysis and borax concentration increased, rheological properties increased due to the increased hydrogen bonding and networking of hyaluronate aggregates. Physical hydrogels from hyaluronic acid and poly(vinyl alcohol) were prepared and the composition dependence of the gels was rheologically investigated as well.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.339-340
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• 2002

Natural castor oil was chemically reconstructed to extend the carbon chains by means of iso-reaction so as to improve the rheological behavior, by way of increasing the viscosity index and decreasing the pour point. The rheological and tribological characteristics of the reconstructed castor oil were comparatively investigated with those of the natural castor oil and several other vegetable oils and a mineral oil. The friction and wear test results on a four-ball machine indicate that the chemically reconstructed castor oil has considerably improved rheological and tribological properties as compared with the natural castor oil. It shows a greatly increase viscosity index and largely decreased pour point, which makes it applicable to low temperature lubrication. The chemically reconstructed castor oil even shows better tribological behavior than pentaerythritol ester or di-iso-capryl sebacate. However, it is still needed to increase the oxidation stability of the reconstructed castor oil.

• 한국식품영양학회지
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• 제4권2호
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• pp.199-206
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• 1991

Rheological properties of $\alpha$-rice powder were investigated in comparison with those of polished rice powder. Flow behavior for cooked solutions of two powdered samples(5~11%) were Binghampseudo plastic. Consistency index and yield stress of cooked solution of powdered a-rice were much lower than those of polished rice powder while flow behavior index was nearly similar. 9% cooked solution of powdered $\alpha$ -rice showed slightly weaker thixotrophic behavior and more ease tendency to relax under the steady shear than those of polished rice powder.

• Journal of Biosystems Engineering
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• 제14권1호
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• pp.8-15
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• 1989

Agricultural materials do not react in a purely elastic manner, and their responses when subjected to stress and strain are appeared from a combination of elastic and viscous behavior. Various researchers have studied the mechanical and rheological properties of the many agricultural materials, but those properties are available mostly foreign varieties of agricultural products. Rheological properties of rice seedlings become important to formulate the principles governing their mechanical behavior. The objectives of this study were to experimentally determine the stress relaxation properties of rice seedlings such as three Japonica-type and one Indica ${\times}$ Japonica hybrid in the transplanting age. The results of this study are summarized as follows; 1. The stress relaxation behavior could be described by the generalized Maxwell model. 2. The phenomenon of stress relaxation happened abruptly just after loading and this phenomenon weakened with the loading time lapsed. 3. With increase of the initial stress, the stress relaxation intensity and residual stress increased, while the relaxation time was constant with increased, while the relaxation time was constant with increase of the level of initial stress. 4. With increase of loading rate, the stress relaxation intensity increased, while the relaxation time and residual stress decreased.

• Macromolecular Research
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• 제14권3호
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• pp.318-323
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• 2006

We investigated the rheological behaviors and orientation of three different types of layered silicate composite systems under external flow: microcomposite, intercalated and exfoliated nanocomposites. Rheological measurements under shear and uniaxial extensional flows, two-dimensional, small-angle X-ray scattering and transmission electron microscopy were conducted to investigate the properties, as well as nano- and micro-structural changes, of polymer/layered silicate nanocomposites. The preferred orientation of the silicate layers to the flow direction was observed under uniaxial extensional flow for both intercalated and exfoliated systems, while the strain hardening behavior was observed only in the exfoliated systems. The degree of compatibility between the polymer matrix and clay determined the microstructure of polymer/clay composites, strain hardening behavior and spatial orientation of the clays under extensional flow.

• 한국축산식품학회지
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• 제43권3호
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• pp.540-551
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• 2023

Milk protein concentrate (MPC) is widely used to enhance the stability and texture of fermented dairy products. However, most research has focused on yogurt products, and the effects of MPC on sour cream characteristics remain unknown. Therefore, we investigated the effects of different MPC levels (0%, 1%, 2%, and 3% w/w) on the rheological, physicochemical, microbiological, and aroma characteristics of sour creams in this study. We found that MPC supplementation stimulated the growth of lactic acid bacteria (LAB) in sour creams, resulting in higher acidity than that in the control sample due to the lactic acid produced by LAB. Three aroma compounds, acetaldehyde, diacetyl, and acetoin, were detected in all sour cream samples. All sour creams showed shear-thinning behavior (n=0.41-0.50), and the addition of MPC led to an increase in the rheological parameters (η_a,50, K, G', and G"). In particular, sour cream with 3% MPC showed the best elastic property owing to the interaction between denatured whey protein and caseins. In addition, these protein interactions resulted in the formation of a gel network, which enhanced the water-holding capacity and improved the whey separation. These findings revealed that MPC can be used as a supplementary protein to improve the rheological and physicochemical characteristics of sour cream.

• 공업화학
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• 제10권5호
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• pp.690-695
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• 1999

석탄핏치로부터 제조된 메조페이스 핏치의 실험적 연구가 용융상태에서의 유변학적 거동을 알아보고자 수행되었다. 겉보기 점도, 전단변형율, 전단응력, 퀴놀린 불용분(QI), 연화점(SP) 변화 등을 조사하여 다음과 같은 결론을 얻었다. 중합시에 메조페이스의 적당한 함량을 증가시키기 위한 조건으로는 열처리 시간이 5시간, 촉매농도는 3%, 반응온도는 $420^{\circ}C$로 나타났다. 온도상승에 따른 겉보기 점도 변화는 핏치의 열처리 조건에 따라 달라지는데 열처리 온도가 높을수록, 열처리 시간이 길어질수록, 메조페이스 함량이 증가할수록 커지며, 유동도는 작아진다. $270^{\circ}C$ 이후의 용융 메조페이스 핏치의 유변학적 거동은 $375^{\circ}C$ 이하에서는 Newtonian fluid의 성질을 띠며 그 이상에서는 Non Newtonian fluid의 거동을 보이며 Casson 모델에 잘 일치됨을 알 수 있었다.

• 한국지반공학회논문집
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• 제27권10호
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• pp.81-92
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• 2011

팽윤성 점토의 전단강도 및 유변학적 특성은 점토입자의 크기, 양이온 교환능력, 점토광물학적 조성과 형상 등에 영향을 받는다. 본 연구는 고운 분말가루의 와이오밍(Wyoming) 벤토나이트에 대해 염화나트륨 0g/L 와 30g/L 농도로 24시간 수화시킨 후 염분농도에 따른 물성-강도특성 및 유변학적 특성변화를 살펴봄으로써, 유변학적 특성, 유변화적 모델들의 적용성 및 흙 입자의 구조변화에 따른 항복응력-점도와의 상관관계를 설명하고자 한다. 실험결과에 따르면, 팽윤성 점토는 전단담화(shear thinning)와 항복응력과 소성점도로 표현가능한 Bingham 유체 거동을 보이는 것으로 조사되었다. 염분농도가 낮고 함수비가 높아질수록 벤토나이트는 완전소성거동에 가깝게 나타나며, 전단변형률속도에 따른 변화의 폭이 미미한 것으로 조사되었다. 반면, 염분농도가 높아질수록 전형적인 전단담화거동을 보이며, 전단변형률속도를 증가시킬수록 염분농도에 따른 벤토나이트의 전단강도의 차이는 커진다. S=0g/L에 대해 Carreau, Herschel-Bulkley 및 멱수법칙 모델이, S=30g/L에 대해서는 이중선형, Herschel-Bulkley 및 멱수법칙 모델 등이 흐름특성을 가장 잘 표현한다. 이것은 염분농도에 따른 흙 입자간 구조적 배열과 형상이 입자간 발생하는 인력인 능-능(EE), 능-면(EF), 및 면-면(FF) 구조를 변화시키고 역학적 특성에 영향을 미치기 때문이다.

• Elastomers and Composites
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• 제49권4호
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• pp.323-329
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• 2014

MIF (Molded-In Foaming) 공법의 발포 거동에 적합한 고분자 기재를 선정하기 위해 SBC (K-resin KK38)와 SBS (KTR 101와 KTR 301)의 유변물성을 측정하였다. SBS의 유변물성 ($G^{\prime}$, $G^{{\prime}{\prime}}$, ${\eta}^*$)은 $155^{\circ}C$와 $170^{\circ}C$의 경우 시간에 따라 유변물성 값의 변화가 거의 없으나, $185^{\circ}C$와 $200^{\circ}C$의 경우에는 시간에 따라 증가하는 것을 볼 수 있었다. 특히, KTR 301의 유변물성 값이 시간에 따라 큰 폭으로 증가하였다. 시간에 따른 유변물성 상승의 정확한 원인을 확인하기 위해 $155^{\circ}C$와 $200^{\circ}C$에서 1800 s 이후의 KTR 301의 비선형 유변물성을 진폭에 대해 측정하였다. $155^{\circ}C$에서는 일반적인 수지와 같은 한 번의 박화(thinning)현상이 관찰되나 $200^{\circ}C$에서는 두 번의 박화현상이 관찰되었고 (Payne effect), 이는 고온에서 SBS가 겔화에 의한 경화가 일어난다고 볼 수 있다. 따라서 이러한 유변물성으로부터 MIF 공법에 요구되는 특성(발포 초기 낮은 점도와 발포 완료 이후 높은 점도)에 적합한 고분자 기재는 SBS KTR 301임을 확인할 수 있었다.