Measuring shear stress at lowest possible shear rates and improving viscosity determination of fat suspensions, for example chocolates

2013 ◽  
pp. n/a-n/a ◽  
Author(s):  
Siegfried Bolenz ◽  
Theresa Tischer
Keyword(s):  
Shear Stress ◽  
Shear Rates ◽  
Viscosity Determination

scholarly journals New Considerations on the Determination of the Apparent Shear Viscosity of Polymer Melt with Micro Capillary Dies

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4451
Author(s):  
Wangqing Wu ◽  
Ke Zeng ◽  
Baishun Zhao ◽  
Fengnan Duan ◽  
Fengze Jiang
Keyword(s):  
Shear Viscosity ◽  
Compaction Pressure ◽  
Experimental Studies ◽  
Polymer Melt ◽  
Rheological Measurement ◽  
Shear Rates ◽  
Micro Scale ◽  
Viscosity Determination ◽  
Main Factor

Capillary rheometers have been widely used for the rheological measurement of polymer melts. However, when micro capillary dies are used, the results are usually neither accurate nor consistent, even under the same measurement conditions. In this work, theoretical modeling and experimental studies were conducted for a more profound understanding of the mechanism by which the initial and boundary conditions influence the inaccuracy in the apparent shear viscosity determination with micro capillary dies (diameters: 500 μm, 200 μm, 100 μm). The results indicate that the amount of polymer initially in the barrel, the pre-compaction pressure and the capillary die diameter have a significant influence on the development of the micro scale inlet pressure, which directly determines the accuracy of the measurement at low and medium shear rates. The varying melt compressibility was confirmed to be the main factor directly related to the inaccuracy in the micro scale apparent shear viscosity determination. It is suggested that measures such as reducing the amount of polymer initially in the barrel and increasing the pre-compaction pressure could be used to reduce the measurement inaccuracy.

Rheological Properties of Two Unvulcanized Rubber Compounds as Determined on an Extrusion and a Rotational Viscometer

1964 ◽  
Vol 37 (2) ◽  
pp. 491-502
Author(s):  
F. E. Devine ◽  
J. A. Ross
Keyword(s):  
Shear Stress ◽  
Rheological Properties ◽  
Extrusion Pressure ◽  
Rheological Parameters ◽  
Shear Stresses ◽  
Extrude Material ◽  
Rotational Viscometer ◽  
Shear Rates ◽  
Rubber Compounds

Abstract The viscometer manufactured by A. Macklow-Smith Ltd., which operates at constant rate of extrusion, is a capillary instrument designed for the determination of flow properties of plastics. The instrument has been used for examining the rheological characteristics of rubber compounds and it has been possible to derive the shear stresses required to extrude material at various shear rates between 2 and 1050 sec−1. The general method of operation of the instrument for this purpose is discussed including the determination of preheat time before extrusion and the aspect of incipient vulcanization in the viscometer during extrusion. The effects of various lengths and diameters of dies on rheological parameters and entrance effects are discussed. An important aspect of the work is the observation of a piston height effect in the extruder barrel. Two different compounded polymers have been examined and in one case, the extrusion pressure was found to decrease with piston height whilst in the other highly elastic material, it was found that as the piston descended, the extrusion pressure increased to an equilibrium value. The importance of this effect in obtaining consistent shear stress data is discussed. Results of the work have been expressed in terms of apparent viscosity and also in terms of the parameters which describe a power law relating shear stress and shear rate within the capillary die. Rheological data have been obtained at various temperatures within the range of processing temperatures of the compounds. The effects on rheological properties of mastication and relaxation time after mastication have been examined. Results have been compared with figures obtained on conventional laboratory viscometers such as the Mooney Plastometer and the Wallace Rapid Plastimeter. A biconical, rotational viscometer has also been used at the lower range of shear rates and the results are compared with those obtained from the extrusion viscometer.

Preventing Wax Deposition in Crude Oil Using Polyethylene Butene and Nano Zinc Oxide

2021 ◽  
Author(s):  
Ademola Balogun ◽  
Toyin Odutola ◽  
Yakubu Balogun
Keyword(s):  
Shear Stress ◽  
Zinc Oxide ◽  
Crude Oil ◽  
Viscosity Reduction ◽  
Waxy Crude Oil ◽  
Nano Zno ◽  
Waxy Crude ◽  
Shear Rates ◽  
Rate Relationship ◽  
Fluid Behaviour

Abstract This research examines the use of 75nm Zinc Oxide nanoparticles (Nano ZnO) and Polyethylene Butene (PEB) in reducing the viscosity of Nigerian waxy crude oil. The rheology of the crude oil was studied by measuring the viscosity and shear stress of crude samples contaminated with varying concentration of PEB (500ppm, 1000ppm, 2000ppm, 3000ppm, 4000ppm and 5000ppm), varying concentrations of Nano ZnO (1wt%, 2wt%, 3wt% and 4wt%) and different blends of PEB and Nano ZnO at temperatures of between 10°C to 35°C and shear rates from 1.7 to 1020s-1. From Rheological Modelling analysis conducted, the Power law pseudoplastic model was the best fit for the experimental data with a regression coefficient of 0.99. Analysis of crude sample before addition of inhibitor showed evidence of non-Newtonian fluid behaviour as the shear stress-shear rate relationship curves were nonlinear due to wax precipitation at low temperatures (10°C to 15°C). The waxy crude demonstrated shear thinning behaviour with increasing shear rates (increasing turbulence) and the viscosity reduced with increasing temperature. The addition of inhibitors (PEB, Nano ZnO and their blends) effected Newtonian fluid behaviour in the crude samples as the shear stress-shear rate relationship curves were linear at all temperatures under study. The optimum concentration of the inhibitors in this study is 2000ppm PEB (causing 33% viscosity reduction) and 1wt% Nano ZnO (effecting 26% viscosity reduction). The best concentration of the blend was 2000ppm PEB blended with 1wt% Nano ZnO which effected a viscosity reduction of 41%. The research demonstrates the novel application of the blend of Nano ZnO and PEB in improving flowability of Nigerian waxy crude oil especially in offshore conditions with prevailing cold temperatures.

scholarly journals Determination of sliding and twinning shear stress during microindentation of Hadfield steel single crystals

2020 ◽  
Vol 10 (4) ◽  
pp. 451-456
Author(s):  
Dmitry Lychagin ◽  
Andrey Filippov ◽  
Olga Novitskaya ◽  
Aleksandr Kolubaev
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Hadfield Steel ◽  
Twinning Shear
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