• Korea-Australia Rheology Journal
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• 제20권4호
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• pp.213-220
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• 2008

The effects of temperature on the rheological properties of the solutions of poly(vinylidene fluoride-co-hexafluopropylene) (PVDF-HFP) in dimethyl acetamide (DMAc) were investigated in terms of frequency and concentration. The effects of temperature on the intrinsic viscosity of the solutions were discussed. In dynamic rheological measurement, the concentrated solutions showed a little unexpected rheological response; as temperature was increased dynamic viscosity was increased and the solutions exhibited more noticeable Bingham body character over the temperature range, 30 to $70^{\circ}C$. In addition, the solution gave longer relaxation time, lower value of loss tangent and higher value of yield stress at higher temperature and at higher concentration. On the other hand, the dilute solutions revealed that intrinsic viscosity was decreased and its Huggins constant was increased with increasing temperature. These physical parameters suggested that the increase of viscosity with increasing temperature resulted from the localized gelation of PVDF-HFP due to reduced solubility to the solvent.

• Bulletin of the Korean Chemical Society
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• 제21권9호
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• pp.875-881
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• 2000

We study the rheological properties of concentrated polymer solution and the melt under simple shear and elon-gational flow using Brownian dynamicssimulation. In order to describe the anisotropic molecular motion, we modifiedthe Giesekus' mobility tensor by incorporating the finitely extensible non-linear elastic (FENE) spring force into dumbbell model. To elucidate the nature of this model, our simulation results are compared with the data of FENE-P ("P"standsfor the Perterin) dumbbell model and experiments. While in steady state both original FENE and FENE-P models exhibit a similar viscosity response,the growthof viscosity becomes dissimilar as the anisotropy decreases and the flowrate increases. The steady state viscosity obtained from the simulation well describes the experiments including the shear-thinning behavior in shear flow and viscosity-thinning behavior in elongational flow. But the growth of viscosity oforiginal FENE dumbbell model cannot describe the experimental results in both flow fields.

• 펄프종이기술
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• 제44권5호
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• pp.54-62
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• 2012

The main role of surface sizing of linerboard is to improve surface and strength properties. Since surface sizing solution is applied on once dried web, substantial amount of drying energy is required. Saving of the drying energy associated with surface sizing can be made by increasing the solids content of the starch solution in size press. Therefore, it is highly desirable to develop low viscosity starches for surface sizing. A low viscosity oxidized starch was prepared and compared its effect of surface sizing with a conventional oxidised starch. Results showed increase in solids content of the starch solution decreased evaporation energy and drying time. Low viscosity starch penetrated deeper into paper and this improve various mechanical properties of linerboard.

• 한국분무공학회지
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• 제14권3호
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• pp.131-138
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• 2009

In the present study, spread-recoil behavior of a drop of shear-thinning liquid (xanthan solution) on a dry wall (polished stainless-steel plate) was examined and compared with that of Newtonian liquid (glycerin solution). Nine different kinds of xanthan and glycerin solutions were tested, including three pairs of xanthan and glycerin solutions, each having the same viscosity in low shear rate region ($10^{-2}-10^0\;l/s$). The drop behavior was visualized and recorded using a CCD camera. The maximum diameter and the spreading velocity of the xanthan drops turned out to be significantly larger and the time to reach their final shape was much shorter compared to the cases with the glycerin solutions, due to the smaller viscous dissipation resulted from lower viscosity in the higher shear rate region (>$10^0\;l/s$). As a result, the maximum diameters were measured to be larger than the predicted values based on the model proposed for Newtonian liquids, and the deviation was more pronounced with the solution with the larger viscosity variation. Consequently, viscosity variation with the shear rate was found to be a dominant factor governing the spread-recoil behavior of shear-thinning drops.

• 펄프종이기술
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• 제47권5호
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• pp.104-111
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• 2015

Factors influencing penetration of PVAm solution into paper during impregnation were investigated with ultrasonic Penetration Evenness Analyzer (PEA). Paper structure was varied by changing basis weight, freeness of pulp, calendering, and filler addition, and hydrophobicity of paper was varied by adding AKD. In addition, the viscosity of PVAm solution was varied by changing the concentration of PVAm solution. Important factors influencing penetration of PVAm solution into paper were found to be the pore structure and the hydrophobicity of paper, and the viscosity of PVAm solution. Pore structure of paper could be controlled by refining degree and filler addition and hydrophobicity of paper could be controlled by internal sizing. Denser structure of paper, higher hydrophobicity and higher liquid viscosity slowed down the penetration of PVAm solution into paper.

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.175-182
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• 2004

Colloidal coating solution was prepared to enhance the hydrophilic property of the film surface. Water and ethanol were used as the dispersion media and (glycidoxypropyl) trimethoxysilane (GPS) as a binder in the colloidal silica coatings. Ethylene diamine was added to the colloidal silica solution as the curing agent. The colloidal silica solution was regarded as a hard-sphere suspension model with low volume fraction of the silica particles. Rheological properties of the silica suspensions modified with GPS have been investigated as a function of pH and concentration. The acidic solution showed high viscosity change by fast hydrolysis reaction and adsorption of the organic binders on the surface of silica particles. However, the hydrolysis was slow at the basic condition and the binders combined with themselves by condensation. The viscosity change was smallest at pH 7. The viscosity increased with the curing time after adding ethylenediamine, and the increase of viscosity at low pH was higher than that at high pH. The hydrophilic properties of the coating film were investigated by the contact angle of water and film surface. The smallest contact angle was shown under the strong acidic condition of pH 2.

• 센서학회지
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• 제17권4호
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• pp.289-294
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• 2008

The purpose of this study is to materialize the viscosity sensor by using the SH-SAW sensor of which the center frequency is operated at higher than 50 MHz. In order to measure the viscosity, SAW sensor of which the center frequency is operated at 100 MHz is developed. By using the developed sensor, phase shift, delay time, insertion loss, and frequency variation are measured at different viscosity. The result shows that the phase shift difference between the viscosity variations is such that the difference between the distilled water and the 100 % glycerol solution is approximately $45^{\circ}$, the change of the insertion loss is approximately 9 dB, and the difference of frequency variation is approximately 5.9 MHz. Therefore, it is shown that viscosity of unknown solution can be measured with the surface acoustic wave sensor.

• 공업화학
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• 제9권2호
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• pp.200-206
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• 1998

수면전개법에 의해 제조된 박막의 두께에 대한 고분자용액의 표면장력과 점도의 영향을 검토하였다. 수면에서 고분자용액의 전개는 고분자용액의 표면장력과 점도에 의해 지배되며, 수면전개 박막의 두께도 이들 인자의 영향을 받는다. 고분자의 농도가 증가함에 따라 고분자용액의 표면장력과 점도는 증가하였으며, 표면장력의 크기는 PVC>PS>CA이었고, 점도의 크기는 CA>PS>PVC 였다. 고분자용액의 수면전개시 물과 고분자용액의 표면장력의 차는 전개구동력으로 작용하나 고분자용액의 표면장력과 점도는 전개저항으로 작용하였다. 수면전개 박막의 두께에 대한 고분자용액의 점도영향이 표면장력에 의한 영향 보다도 더 컸으며, 수면 전개 박막의 두께는 PS>CA>PVC 순으로 두꺼웠다.

• 문화기술의 융합
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• 제9권4호
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• pp.331-335
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• 2023

혈액의 점도가 높아질수록 혈액은 더 끈적하고 흐름이 어려워지므로 혈전의 발생 가능성이 높아져 허혈성 뇌경색의 발생 확률이 증가한다. 혈액 점도 측정은 최근 순환기계 질환의 예방을 위하여 그 중요성이 강조되고 있으며 혈액의 점도를 쉽고 정확하게 측정할 수 있는 점도계의 필요성이 대두되고 있다. 본 연구에서는 평행판 점도계 ARS-Medi에 의한 점도표준액과 인공혈액의 측정값들을 국제적으로 정확성과 신뢰성을 인정받는 TA instrument의 Ares-G2로 측정한 값들과 비교하였다.. 뉴턴성 용액인 N44 표준용액의 점도는 모든 전단율에서 두 기기 간에 거의 완벽하게 일치하였다, 비뉴턴성 용액인 인공혈액의 경우 가장 낮은 전단율인 1 rad/s 에서는 약 10%의 차이를 보였으나, 임상적으로 유의한 전단율인 10 rad/s 이상에서는 두 기기간의 측정값이 오차범위 내에서 모두 일치하였다. 우리는 새로 개발한 혈액 전용 평행판형 점도계 ARS-Medi가 1회용 평행판을 사용하므로 혈액 점도 측정의 편의성과 위생성이 향상되어 임상에 매우 유용할 것으로 기대한다.

• East Asian mathematical journal
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• 제38권1호
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• pp.129-141
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• 2022

We obtain interior regularity estimates in the weighted Orlicz spaces for viscosity solutions of fully nonlinear uniformly parabolic equations u_t - F(D² u, x, t) = f(x, t) in Q₁ under relaxed structure conditions on the nonlinear operator F.