scholarly journals Flow-Induced Crystallization of PB-1:  From the Low Shear Rate Region up to Processing Rates

2006 ◽  
Vol 39 (26) ◽  
pp. 9215-9222 ◽  
Author(s):  
Jimmy Baert ◽  
Peter Van Puyvelde ◽  
Florentin Langouche
Keyword(s):  
Shear Rate ◽  
Rate Region ◽  
Induced Crystallization ◽  
Flow Induced Crystallization ◽  
Low Shear

Formation of cylindrite structures in shear-induced crystallization of isotactic polypropylene at low shear rate

Polymer ◽  
2007 ◽  
Vol 48 (4) ◽  
pp. 1105-1115 ◽  
Author(s):  
Chenggui Zhang ◽  
Haiqing Hu ◽  
Xiaohong Wang ◽  
Yonghua Yao ◽  
Xia Dong ◽  
...  
Keyword(s):  
Shear Rate ◽  
Isotactic Polypropylene ◽  
Induced Crystallization ◽  
Low Shear

Effect of Gel and Nonrubber Constituents on the Extrusion Properties of Guayule Rubber

1983 ◽  
Vol 56 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Sergio A. Montes ◽  
M. A. Ponce-Vélez
Keyword(s):  
Experimental Study ◽  
Shear Rates ◽  
Paraffinic Oil ◽  
Induced Crystallization ◽  
Flow Induced Crystallization ◽  
Low Shear

Abstract An experimental study on the effect of gel and nonrubber constituents on the extrusion behavior of guayule rubber (GR) has been carried out. At 140°C, gel increases the viscosity at low shear rates. When GR is properly stabilized, no peptizing effect is imparted by the resin. However, the resin acts as a moderate plasticizer as compared to paraffinic oil. At 120°C, the effect of gel is noticeable at high extrusion rates, increasing the viscosity, suggesting an increase in the tendency for the occurrence of flow-induced crystallization.

Hysteresis Behaviors of Poly (Naphthalene Quinone) Radical Electrorheological Fluid

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1901-1907 ◽  
Author(s):  
Hyoung J. Choi ◽  
Min S. Cho ◽  
Myung S. Jhon
Keyword(s):  
Shear Rate ◽  
Silicone Oil ◽  
Electrorheological Fluid ◽  
Shear Stresses ◽  
Hysteresis Phenomenon ◽  
Rate Region ◽  
Er Fluids ◽  
High Voltage Generator ◽  
Er Fluid ◽  
Low Shear

As a potential electrorheological(ER) material, poly(naphthalene quinone) radical (PNQR) ER fluid was prepared, and its rheological behavior and hysteresis phenomenon were investigated. PNQR was synthesized by Friedel-Crafts acylation between naphthalene and phthalic anhydride, using zinc chloride as a catalyst at 256°C. A Physica rheometer equipped with a high voltage generator was used to measure the rheological properties of the ER fluids, which were prepared by dispersing PNQR in silicone oil at several particle concentrations. Shear stresses were observed to decrease as shear rate increased in the region of slow deformation rate. It was further found that ER fluid showed different hysteresis behaviors according to the shear rate ranges; thixotropy was observed in the low shear rate region (0.007-0.51/s) and anti-thixotropy in the high shear rate region (0.5-10001/s). Controlled shear stress mode was also applied to observe similar behaviors.

Rheological Modelling of Complex Flow Behaviour of Bitumen-Solvent Mixtures and Implication for Flow in a Porous Medium

2021 ◽  
pp. 1-34
Author(s):  
Olalekan Alade
Keyword(s):  
Shear Rate ◽  
Power Law ◽  
Rheological Model ◽  
Flow Characteristics ◽  
Solvent Mixtures ◽  
Pore Scale ◽  
Rheological Models ◽  
Shear Rates ◽  
Rate Region ◽  
Low Shear

Abstract The viscosity of extra-heavy oils including bitumen can be reduced significantly by adding solvent such as toluene to enhance extraction, production and transportation. Thus, prediction of viscosity and/or rheology of bitumen-solvent mixtures has become necessary. More so, selecting a suitable rheological model for simulation of flow in porous media has an important role to play in engineering design of production and processing systems. While several mixing rules have been applied to calculate the viscosity of bitumen-solvent mixtures, rheological model to describe the flow characteristics has rarely been published. Thus, in this investigation, rheological behaviour of bitumen and bitumen-toluene mixtures (weight fractions of bitumen WB = 0, 0.25, 0.5, 0.6, 0.75, and 1 w/w) have been studied at the flow temperature (75 °C) of the bitumen and in the range of shear rates between 0.001 and 1000 s−1. The data was fitted using different rheological models including the Power Law, Cross Model, Carreau-Yasuda Model, and the newly introduced ones herein named as Cross-Logistic and Logistic models. Then, a computational fluid dynamics (CFD) model was built using a scanning electron image (SEM) of rock sample (representing a realistic porous geometry) to simulate pore scale flow characteristics. The observations revealed that the original bitumen exhibits a Newtonian behaviour within the low shear rate region (0.001 to 100 s−1) and shows a non-Newtonian (pseudoplastic) behaviour at the higher shear rate region (100 to 1000 s−1). Conversely, the bitumen-toluene mixtures show shear thinning (pseudoplastic) behaviour at low shear rate region (0.001 to 0.01), which appears to become less significant within 0.01 to 0.1 s−1, and exhibit shear independent Newtonian behaviour within 0.1 and 1000 s−1 shear rates. Moreover, except for the original bitumen, statistical error analysis of prediction ability of the tested rheological models as well as the results from the pore scale flow parameters suggested that the Power Law might not be suitable for predicting the flow characteristics of the bitumen-toluene mixtures compared to the other models.

Flow-Induced Crystallization: Unravelling the Effects of Shear Rate and Strain

2010 ◽  
Vol 43 (19) ◽  
pp. 8136-8142 ◽  
Author(s):  
Ahmad Jabbarzadeh ◽  
Roger I. Tanner
Keyword(s):  
Shear Rate ◽  
Induced Crystallization ◽  
Flow Induced Crystallization

scholarly journals Dynamic Viscosity As A Function Of Shear Rate: The Comparison Of Established Rheological Models With The Newly Derived Rheological Model For The Estimation Of Zero– And Infinite–Shear Rate Viscosity Of Vegetable Oils

2012 ◽  
Author(s):  
Eng Giap Sunny Goh ◽  
Azira Amran
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Vegetable Oil ◽  
Rheological Model ◽  
Physical Parameters ◽  
Extreme Conditions ◽  
Newtonian Viscosity ◽  
Rheological Models ◽  
Rate Region ◽  
Low Shear

Kelikatan merupakan salah satu daripada parameter fizikal penting yang memerlukan pengukuran dengan kejituan, dan supaya ia dapat diwakili dengan persamaan reologi untuk membolehkan interpolasi nilai kelikatan yang tidak diketahui. Persamaan akan mempunyai kelebihan tambahan jika anggaran persamaan mampu memberi anggaran jitu penentuluaran. Sesetengah persamaan adalah mementingkan kejituan ramalan kelikatan dalam julat nilai eksperimen, sementara yang lain pula boleh membuat jangkaan kelikatan pada keadaan lampau, contohnya, kelikatan pada keadaan infiniti– and sifar–keterikan. Persamaan Cross and Carreau mampu untuk memberi nilai kelikatan pada keadaan lampau, tetapi anggaran keterikan awalan tidak boleh ditentusahkan jika data eksperimen tidak menunjukkan kewujudan sifat Newtonian. Dalam kajian ini, minyak tumbuhan kelapa, jagung, canola, dan soya dikaji dengan menggunakan viskometer pada keterikan yang berlainan, 3.9 – 131.6 s–1, dan keterikan adalah dilakukan pada suhu, 50 dan 90°C. Data eksperimen dipadankan dengan persamaan–persamaan reologi yang terkenal, dan kemudiannya, satu persamaan reologi baru diperkenalkan sebagai persamaan altenatif kepada pengiraan kelikatan pada kawasan keterikan rendah. Infiniti–keterikan kelikatan daripada persamaan baru adalah setara dengan nilai–nilai daripada persamaan–persamaan reologi terkenal. Di samping itu, keputusan menunjukkan kelikatan minyak tumbuhan mempunyai ciri pseudoplastic, dan data eksperimen dapat dimodelkan dengan persamaan baru dengan baik (R2 > 0.96). Kata kunci: Kelikatan; keterikan; reologi; minyak tumbuhan; Newtonian Viscosity is one of the most important physical parameters that need proper measurement in terms of its accuracy, and to be fitted by rheological model to enable interpolation for unknown viscosity. It would be an advantage if the model estimation could be extended for viscosity extrapolation with reliability. Some models are concerned with the accuracy of predicting viscosity within the experimental range value, while others able to predict viscosity at extreme conditions, for instance, viscosity at infinite– and zero–shear rate conditions. Cross and Carreau are able to model viscosity at extreme conditions, but its estimation value at very low shear rate region could not be justified if the experimental data does not signify the presence of Newtonian behaviour. In this study, coconut, corn, canola, and soy oils were investigated with a viscometer at different shear rates, 3.9 – 131.6 s–1, and were sheared at specific temperatures, 50 and 90°C. The experimental data were curve–fitted with wellknown rheological models, and then, a new rheological model was proposed as an alternative equation for viscosity estimation at low shear rate region. Infinite–shear rate viscosity from the new model is consistent with the estimation from well–known models. In addition, results showed that vegetable oil has the characteristic of a pseudoplastic, and the experimental data were well fitted by the new proposed model (R2 > 0.96). Key words: Viscosity; shear rate; rheology; vegetable oil; Newtonian

Melt flow properties of graphite nanoplatelets-filled polypropylene

2016 ◽  
Vol 51 (19) ◽  
pp. 2793-2804 ◽  
Author(s):  
Ayse B Bas ◽  
Oktay Yilmaz ◽  
Anil Ibis ◽  
Mustafa Dogu ◽  
Kadir Kirkkopru ◽  
...  
Keyword(s):  
Shear Rate ◽  
Polymer Matrix ◽  
Shear Viscosity ◽  
Volume Fraction ◽  
Shear Thinning ◽  
Filler Concentration ◽  
Graphite Nanoplatelets ◽  
Rate Region ◽  
Graphite Composites ◽  
Low Shear

Rheological behavior of polypropylene/graphite nanoplatelet composites of varying content, temperature, and filler shape was investigated by capillary and rotational rheometers. Scanning electron microscope images were taken in order to examine the filler shape and interaction between fillers and polymer matrix. Viscosity measurements of polypropylene/graphite composites showed shear thinning behavior like neat polypropylene. Filler inclusion resulted in increase in shear viscosity and shear thinning behavior of composites. The effect of filler concentration on viscosity is more appreciable in the low shear rate region. PP/graphite nanoplatelet composites with larger interface between filler and polymer matrix were of greater shear viscosity values through the entire shear rate range. However, filler morphology did not affect shear viscosity in high shear rate region remarkably. Composite viscosity as a function of volume fraction was modeled by Maron–Pierce equation. As temperature increased, shear viscosities of polypropylene/graphite composites and neat PP melt decreased. Temperature has less effect on composite viscosity than on neat PP viscosity due to the restricting effect of fillers on polymer molecules.

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