scholarly journals Vliv smykové viskozity a elasticity na senzorickou viskozitu modelových kapalných potravin

1999 ◽  
Vol 17 (No. 1) ◽  
pp. 23-30 ◽  
Author(s):  
P. Novotna ◽  
M. Houska ◽  
V. Sopr ◽  
H. Valentova ◽  
P. Stern
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Shear Viscosity ◽  
Normal Stress Difference ◽  
Rheological Parameters ◽  
Cellulose Derivatives ◽  
Moderate Increase ◽  
Stress Difference ◽  
First Normal Stress Difference ◽  
Normal Difference

The shear flow rheological properties of sugar solutions (70% w/w concentration) modified by different cellulose derivatives have been measured. Thickeners  were expected to cause the viscoelastic behaviour of the resulting sol ution. Therefore, the elastic rheological parameters were measured by oscillatory shear technique (phase angle, elastic modulus) and also the first normal stress difference N<sub>1</sub>. The increase of thickener concen tration caused a moderate increase of non-Newtonian behaviour in the shear flow. The sensory viscosity (ra nged between 0 and 100%) was evaluated by five different methods - as an effort for stirring with teaspoon, time for flowing down the spoon, slurping from spoon, compression between tongue and palate and swallowing. The influence of shear viscosity and first normal difference on sensory viscosity was tested. Correlation procedu re between change of sensory viscosity .tlSE and change of shear viscosity .tlJ.Iz showed that only for swallowing there is a statistically evident de­pendence. The correlation between change of sensory viscosity t.SE and first normal stress difference N<sub>1</sub> is not statistically   evident. For all the methods of sensory evaluation the dependence between these parameters is only weak and indirect (with increasing normal stress difference the sensory viscosity is decreasing).

The first normal stress difference of non-Brownian hard-sphere suspensions in the oscillatory shear flow near the liquid and crystal coexistence region

Soft Matter ◽  
2020 ◽  
Vol 16 (43) ◽  
pp. 9864-9875
Author(s):  
Young Ki Lee ◽  
Kyu Hyun ◽  
Kyung Hyun Ahn
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Hard Sphere ◽  
Normal Stress Difference ◽  
Oscillatory Shear ◽  
Stress Difference ◽  
Large Amplitude Oscillatory Shear ◽  
First Normal Stress Difference ◽  
Oscillatory Shear Flow ◽  
Sphere Suspensions

The first normal stress difference (N1) as well as shear stress of non-Brownian hard-sphere suspensions in small to large amplitude oscillatory shear flow is investigated.

Numerical Simulation of a First Normal Stress Difference-Based Model for Shear-Induced Crystallization of Polyethylene

2011 ◽  
Vol 266 ◽  
pp. 130-134
Author(s):  
Jin Yan Wang ◽  
Jing Bo Chen ◽  
Chang Yu Shen
Keyword(s):  
Numerical Simulation ◽  
Shear Flow ◽  
Normal Stress ◽  
Viscoelastic Model ◽  
Normal Stress Difference ◽  
Simple Shear Flow ◽  
Stress Difference ◽  
Avrami Model ◽  
First Normal Stress Difference ◽  
Induced Crystallization

The paper presents a numerical simulation for the isothermal flow-induced crystallization of polyethylene under a simple shear flow. The effect of flow on crystllization is considered through the simple mathematical relationship between the additional number of nuclei induced by shear treatment and the first normal stress difference. Leonov viscoelastic model and Avrami model are used to describe the normal stress difference and the crystallization kinetics, respectively. It is found that the short-term shear treatment has a large effect on the crystallization dynamics of polyethylene , but the effect of the intensity of the shear flow is not infinite ,which shows a saturation phenomenon, namely, the accelerated degree of crystallization tending to level off when the shear rate or shear time is large enough.

Rheological Behaviour of PP/PET and Modified PP/PET Blends. I. Steady State Flow Properties

2003 ◽  
Vol 11 (6) ◽  
pp. 487-503 ◽  
Author(s):  
Natalie Zdrazilova ◽  
Berenika Hausnerova ◽  
Takeshi Kitano ◽  
Petr Saha
Keyword(s):  
Maleic Anhydride ◽  
Normal Stress ◽  
Shear Viscosity ◽  
Rheological Behaviour ◽  
Normal Stress Difference ◽  
Stress Difference ◽  
Flow Properties ◽  
Complex Situation ◽  
First Normal Stress Difference ◽  
The Matrix

Both polypropylene (PP) and polyethylene terephthalate (PET) constitute a significant portion of post-consumer waste. To improve the recycling of immiscible PP/PET blends, a compatibiliser should be utilised. The steady shear flow properties of unmodified and modified PP/PET blends having up to 50 wt.% PET were investigated and compared in this study. Three types of PPs with different flow properties were used to ascertain the influence of the matrix on the blend's rheology. The effect of modification on the rheological properties was evaluated in two ways - firstly, the addition of 1 wt.% of maleic anhydride (MA), and secondly, the use of already modified polypropylene. According to the morphological observations, an improvement in compatibility was found in both cases. The shear viscosity and the first normal stress difference were measured using a rotational cone and plate rheometer at 265°C (when both PET and PP are molten), and 245°C (when only PP has melted). Completely different behaviour was observed under these two temperature conditions. At 265°C, the shear viscosity decreases with PET content in the blend, while at 245°C it increases, thus recalling the behaviour of particle-filled systems. The addition of maleic anhydride affects the shear viscosity in various ways; a decrease, an increase, and some almost unchanged values were obtained. Concerning the first normal stress difference, an even more complex situation occurs, and the effect of modification by MA is also ambiguous. Furthermore, the deviations from the log-additivity rule were evaluated in terms of the shear viscosity and the first normal stress difference. From the results, it can be supposed that PP-X/PET samples were compatibilised successfully, and strong interphase interactions could be expected. Finally, the yield values of shear stress determined at 245°C showed a generally increasing tendency with increasing PET content.

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