• 폴리머
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• 제38권2호
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• pp.225-231
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• 2014

고분자 결합제로 vinyl acetate(VA) 함량이 각각 30, 60%인 poly(ethylene-co-vinyl acetate)(EVA)를 사용하여 고농축 복합화약 시뮬란트의 유변학적 특성을 연구하였다. 충전제로는 탄산칼슘 및 research department explosive (RDX)와 물리적 특성이 유사한 Dechlorane을 사용하였다. 회분식 용융 혼련기를 사용하여 농축 현탁계를 혼련하였는데 최대 75 v%까지 충전이 가능하였다. 동적 기계적 물성 변화를 측정한 결과 Dechlorane이 탄산칼슘보다 결합제수지와 더 높은 상호작용을 보였다. 일정 전단속도 방식과 일정 전단응력 방식의 평판-평판 레오미터를 사용하여 현탁계의 미세구조의 변화가 유변물성에 미치는 영향을 조사하였고, Krieger-Dougherty 식을 사용하여 최대 충전 부피분율 및 고유점도를 구하였다. EVA31/Dechlorane 현탁계의 최대 충전 부피분율은 약 70 v%이고, 혼련시 전단응력이 약 2000 Pa 정도 부가되는 것이 적절함을 알 수 있었다.

• 펄프종이기술
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• 제40권1호
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• pp.1-8
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• 2008

It is essential to use base papers having proper surface characteristics in coating operation for improving coated paper quality and coater runnability. To fulfill these purposes, surface sizing of coating base stock with oxidized starch is commonly practiced. Use of cationic starch for surface sizing improves coated paper quality since cationic starch penetrates less into paper structure. The immediate objective of this study was to examine the influence of surface sizing with starch solutions containing cationic polymers on the rheology of coating colors and the effect on physical properties of coated papers. Changes of rheological characteristics of coating colors placed on the plastic substrate surface sized with cationic and anionic starch were determined. Results of rheological test showed that cationic polymer surface sizing agent increased electrostatic interaction with coating colors and increased storage modulus. This new technology of using cationic polymer as surface sizing additive was considered to be advantageous for base papers at low basis weights since it would improve the coverage and optical properties of coated papers.

• Applied Biological Chemistry
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• 제40권1호
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• pp.48-52
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• 1997

다양한 가공 적성을 갖는 변성 전분을 토마토 케찹의 제조에 첨가하여 변성 전분의 종류 및 첨가량이 토마토 케찹의 유동 특성, 층분리 및 관능적 성질에 미치는 영향에 관하여 조사하였다. 케찹을 Herschel-Bulkley계 유체로 간주하여 분석한 결과 항복응력와 점조도지수는 ADA(acetylate distarch adipate)>SA(starch acetate)>HDP(hydroxypropyl distarch phosphate)>RCS(raw corn starch)>NS(no starch)의 순으로 크게 나타났으며 거동유동지수는 SA와 HDP의 경우 첨가량에 관계없이 거의 일정하였으나 ADA와 RCS는 첨가량이 증가할 수록 감소하는 경향을 보였다. 원심분리에 의한 층분리 검사에서는 ADA>SA>HDP>RCS>NS의 순으로 층분리가 방지되는 안정성을 나타냈다. 관능검사 결과 전반적으로 ADA(2%)>SA(2%)>RCS(2%)>NS>HDP(2%)의 순으로 기호도가 높게 나타났다.

• Plant Biotechnology Reports
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• 제5권4호
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• pp.345-352
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• 2011

The rheological and diffusion properties of blends of agar/guar gum, agar/Phytagel and Phytagel/guar gum were analysed and compared to those properties of agar or Phytagel applied alone at two different gelling concentrations. Moreover, their effects on the shoot multiplication of the apple scion Galaxy and two black locust clones (SF63, SF82) were studied, and their cost benefits over agar were calculated. Elastic hydrogel formation was demonstrated for each blend by rheological measurements, but the gel strength depended on the types and concentrations of the applied gelling agents and blends. Guar gum was able to speed the diffusion in the different blends, and diffusion was independent of gel strength. The rate of shoot multiplication increased (to 8.9 shoots per explant) and the percent of hyperhydrated shoots decreased (to 12%) when the blend of agar/guar gum was used for the shoot multiplication of apple. Similarly, the highest multiplication rates of black locust clones (between 3.9 and 4.1) were obtained on media solidified by blends containing guar gum. The best shoot performance with the lowest percent of hyperhydrated shoots (11-12% in SF63 and 2-23% in SF82) was achieved using agar alone or the agar/guar gum blend. The shoot multiplication was improved of both species and the production cost was reduced by 42% by using the agar/guar gum blend.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.316-322
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• 2002

This paper presents the temperature-dependent hysteresis identification of an electro-rheological (ER) fluid under various operating temperatures using the Preisach model. As a first step, polymethylaniline (PMA) particles are prepared and mixed with silicone oil to make an ER fluid. A couette type electroviscometer is then employed to obtain the field-dependent shear stress. In order to show the suitability of the Preisach model to predict a physical hysteresis phenomenon of the ER fluid, two significant properties; the minor loop property and the wiping-out property are experimentally examined under three dominant temperature conditions. Subsequently, the Preisach model fur the PMA-based ER fluid is identified using experimental first order descending (FOD) curves. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one under the both specified and unspecified temperatures. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• 한국소음진동공학회논문집
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• 제12권8호
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• pp.648-656
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• 2002

This paper presents the identification of temperature-dependent hysteresis of an electro-rheological (ER) fluid under various operating temperatures using the Preisach model. As a first step, polymethylaniline (PMA) particles are prepared and mixed with silicone oil to make an ER fluid. A couette type electroviscometer is then employed to obtain the field-dependent shear stress. In order to show the suitability of the Preisach model to predict a physical hysteresis phenomenon of the ER fluid, two significant properties; the minor loop property and the wiping-out property are experimentally examined under three dominant temperature conditions. Subsequently, the Preisach model for the PMA-based ER fluid is identified using experimental multiple first order descending (FOD) curves. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one under the both specified and unspecified temperatures. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• 한국축산식품학회:학술대회논문집
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• 한국축산식품학회 1997년도 제18차 정기총회 및 학술발표회
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• pp.19-39
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• 1997

Extrusion conditions were optimized for blends of ground lamb and starch using a single-screw extruder for the purpose of producing expanded snack-type products. A central composite rotatable response surface methodology(RSM) design was used with variation in feed moisture, process temperature, and screw speed. The three variables significantly affected one or more of the measured physical properties of extrudates. The optimum conditions for minimum shear force values were 26.5% feed moisture, $148^{\circ}C$ process temperature, and 134 rpm screw speed. Lean ground beef, chicken, goat, lamb or mutton was blended with corn starch, and extruded at the optimum condition established from RSM experiments. Physical/rheological properties were generally similar, water activity was low (<0.12) and total aerobic plate counts were <10 for all products. Extrudates containing chicken had the highest ratio of polyunsaturated fatty acids to saturated fatty acids, whereas those containing beef had the highest ratio of monounsaturated fatty acids to saturated fatty acids. Sensory data indicated that texture was acceptable and flavor characteristics were not different among the products.

• Macromolecular Research
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• 제9권1호
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• pp.30-36
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• 2001

Polybutadiene latex grafted (g-PB) in g-PB/SAN blends, i.e., acrylonitrile-butadiene-styrene terpolymer (ABS) were partially replaced by acrylonitrile-butadiene copolymer (NBR) with various acrylonitrile (AN) contents. Changes in morphology, physical and rheological properties were examined. The dispersed size of NBR was decreased as the miscibility with matrix SAM, was increased by increasing AN content in NBR upto 50 wt%. Impact strength was enhanced about two-fold due to the NBR dispersed with a slight larger size than the original g-PB. Gloss was effectively reduced as the particle size of NBR was increased. Tensile yield strength was decreased, and elongation at break or yield behavior at low shear rate were increased as g-PB was partially replaced by NBR having AN content less that 40 wt%.

• Macromolecular Research
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• 제17권3호
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• pp.156-162
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• 2009

Supramolecular hydrogels were instantaneously fabricated by mixing aqueous solutions of $\alpha$-cyclodextrins ($\alpha$-CDs) and amphiphilic methoxy (polyethylene glycol) (MPEG)-$\varepsilon$-caprolactone (CL) oligomer, which was synthesized via the ring-opening polymerization of the CL monomer using low-molecular-weight MPEG ($M_n$ of MPEG=2,000 g/mol) as an initiator. The supramolecular structure of the hydrogels was revealed by X-ray diffraction (XRD) analyses. Rheological studies of the hydrogels revealed an elastic character when the number of CL units in the oligomer was more than 2, and the obtained hydrogels showed high storage modulus but relatively low shearing viscosity due to the low-molecular-weight character of the oligomer, which was more preferable for use as an injectable delivery system. The physical properties of the hydrogels could be modulated by controlling the chain morphology and concentration of the oligomers, as well as the feed molar ratio of the oligomer to $\alpha$-CD. The components of the supramolecular hydrogels are biocompatible and can readily be eliminated from the body. These features render the supramolecular hydro gels suitable as drug delivery systems and tissue engineering scaffolds.

• 한국자기학회지
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• 제5권5호
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• pp.667-671
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• 1995

The viscometric technique is used to study the effects of microstructure on the viscosity (viscosity vs. concentration or shear rate) of magnetic particle suspensions. In this characterization, measurement of suspension viscosity is used to obtain the dependence of viscous energy dissipation on microstructural state of dispersions. Microstructural shape effects which are related to particle orientation are then indirectly obtained. Empirical formulas from mean field theory and the Mooney equation, which are applicable at high concentration of magnetic particles, are used to relate viscosity to particle concentration. The validity and physical meaning of these equations are discussed.