scholarly journals A new slit‐radial die for simultaneously measuring steady state shear viscosity and first normal stress difference of viscoelastic liquids via capillary rheometry

2022 ◽  
pp. 52094
Author(s):  
Masood Khabazian Esfahani ◽  
Christos K. Georgantopoulos ◽  
Ingo F. C. Naue ◽  
Joachim Sunder ◽  
Manfred Wilhelm
Keyword(s):  
Steady State ◽  
Normal Stress ◽  
Shear Viscosity ◽  
Normal Stress Difference ◽  
Stress Difference ◽  
Capillary Rheometry ◽  
First Normal Stress Difference ◽  
Viscoelastic Liquids

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).

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.

Rheology of LCP/PET Blends at Solid and Molten States of LCP

2006 ◽  
Vol 16 (3) ◽  
pp. 152-160 ◽  
Author(s):  
S.A.R. Hashmi ◽  
Takeshi Kitano
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Shear Viscosity ◽  
Liquid Crystalline ◽  
High Sensitivity ◽  
Crystalline Polymer ◽  
Normal Stress Difference ◽  
Stress Difference ◽  
First Normal Stress Difference ◽  
Different Temperatures

Abstract Liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) were blended in an elastic melt extruder to make samples having different volume fractions of constituent polymers. Shear stress, shear viscosity, first normal stress difference at different shear rates under steady state conditions of these blends were evaluated at two different temperatures 265 and 285˚C. The LCP was in solid state at 265˚C and in melt state at 285˚C and was dispersed in molten matrix of PET at both temperatures. Shear viscosity of blend increased with addition of LCP in PET matrix. A maxima was observed in viscosity versus composition plot. Blends containing more than 50 vol. % of LCP in the blend show higher viscosity as compared to the constituent polymers. First normal stress difference, N1, increased with LCP content in the blend at 285˚C when ploted against shear stress whereas at 265˚C this trend was opposite. The increased value of N1 with shear rate was explained assuming a tendency of asymmetric particles to rotate under velocity gradient of suspending medium. At 285˚C N1 varied with shear stress in two stages. First stage was characterized with high sensitivity of N1 with shear stress, which reduced in second stage on plastic deformation of LCP droplets.

Polyethyene melt-flow examined with time-dependent thermodynamics

2016 ◽  
Vol 49 (3) ◽  
pp. 258-264
Author(s):  
Nobuyuki Nakajima
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Normal Stress ◽  
Energy Production ◽  
Normal Stress Difference ◽  
Stable Region ◽  
Steady State Flow ◽  
First Normal Stress Difference ◽  
Volume Increase ◽  
State Flow

Time-dependent thermodynamics was applied to steady-state melt flow of polyethylene. The steady-state viscosity behavior and first normal-stress difference were examined as a couple. The latter was a measure of the energy intensity (energy per volume); the time derivative of that was treated as the rate of energy production. In steady-state flow, viscosity decreased and the rate of the energy production increased with increasing shear stress. From the sign of the rate of production, steady flow was found to be in the stable region. The stress growth leading into steady-state flow was known from our previous work to be in the unstable region. This may be called pseudo-stable region. Under a constant rate of shear deformation, both shear stress and viscosity increased rapidly. A change into steady-state flow was interpreted to be the fracture point. The growth of the normal stress was slower than that of shear stress. The first normal-stress difference was a manifestation of deformation, which is a volume increase caused by shear stress. The volume increase led to fracture.

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