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Viscometric Techniques
Published in Nicholas P. Cheremisinoff, Polymer Mixing and Extrusion Technology, 2017
Another rheological test more often used for product quality control is measurement of the elastic recovery in polymer melts and their compounds. This is usually done by measuring the swell (or shrinkage) of materials undergoing extrusion. The tendency of polymers, whether thermoplastic or rubber, to enlarge when emerging from an extruder die is called die swell. Die swell normally refers to the ratio of extruded size to die size. This behavior is a measure of the relative elasticity in the flowing polymer stream. Die swell is caused by the release of the residual stresses when the sample emerges from the die. Measurement of this behavior has become widely recognized in the rubber and plastics industries as an important indication of polymer processibility.
Conventional Viscometers and General Concepts
Published in Nicholas P. Cheremisinoff, An Introduction to Polymer Rheology and Processing, 1993
Rheological test more often used for product quality control is a measurement of the elastic recovery in polymer melts and their compounds. This is usually accomplished by measuring the swell (or shrinkage) of materials undergoing extrusion. The tendency of polymers, whether thermoplastic or rubber, to enlarge when emerging from an extruder die is called die swell. Die swell normally refers to the ratio of extruded size to die size. This behavior is a measure of the relative elasticity in the flowing polymer stream. Die swell is caused by the release of the residual stresses when the sample emerges from the die. Measurement of this behavior has become widely recognized in the rubber and plastics industries as an important indication of polymer processability.
Characteristics of Polymers and Polymerization Processes
Published in Manas Chanda, Plastics Technology Handbook, 2017
A consequence of viscoelasticity of polymer melt is die swell, which refers to the fact that the thickness of the melt emerging through a narrow orifice or die is greater than the width of the die opening. This is explained as follows: as the molecules flow rapidly through the die opening, they are compressed, and when they emerge, the resultant reduction in pressure causes the molecules to rebound to a degree. This dimensional increase of the extrudate must be taken into account by engineers who design polymer processing machinery (Chapter 2).
Increasing perpendicular alignment in extruded filament by an orifice embedded 3D printing nozzle
Published in Virtual and Physical Prototyping, 2022
Do-In Jeong, Ankur Jain, Dong-Wook Oh
Three different flow rates at the inlet – 0.1, 0.2 and 0.4 mL/min – were simulated, identical to experiments. Pressure at the exit was set as 0 Pa. The no-slip condition was applied at the internal wall of the nozzle flow channel, and shear stress at the walls was set as zero after the nozzle exit. Simulations were carried out on the four nozzle flow channel configurations presented in Figure 3, which is identical to the flow visualisation experiments. Analysis was performed up to 10 mm downstream of the nozzle exit. The overall geometry of the simulation models is shown in Figure 5. The diameter of the cylinder extruded filament after the nozzle exit was determined to be 1.2 mm by flow visualisation image analysis. This value is larger than the nozzle diameter of 1 mm because of die swell of the PDMS and fibre mixture.
Magnetized dissipative Soret and Dufour effects on thermally radiative Casson fluid flow over a stretching cylinder with Cattaneo–Christov heat and mass flux models
Published in Waves in Random and Complex Media, 2023
The boundary layer flow of Newtonian/non-Newtonian fluids over-stretching objects has a significant role in many of the practical situations of science and engineering and has plenty of real-life applications such as wire drawing, wind currents due to open central solar receivers, process of polymer extrusion, cooling of transpiration and lubricants performance and many more manufacturing phenomena. Pertaining to this, the Prandtl boundary layer flow of Newtonian/non-Newtonian fluids brought by elongating sheets/surfaces/cones and cylinders has received the substantial attention of researchers and scientists. The governing flow equations of aforementioned practical situations representing the non-Newtonian fluid behavior are highly complicated in characteristics hence; the Prandtl flow behavior is not easy to determine through the restricted mathematical equations. Hence, it requires the current scientific era to forestall the inherent features of those types of fluid flows owing to their industrial and technological applications. Accordingly, the scientists and engineers have identified the research gaps that can be compensated by emerging effective numerical/analytical schemes and that will balance the technicalities of the physical situations and gives the comprehensive visualization of various non-Newtonian fluid models. Fundamentally, the non-viscous flow systems are grouped into three different categories on the basis of their behavior, i.e. steady, unsteady and viscoelastic; however, the Casson model visualizes the apparent viscosity impacts on the flow in the steady-state condition. In addition, these flows have macroscopic applications in industrial processes such as mountaineering of rods; electronic device cooling, solar energy collectors and die swell. After the scientific partition of these non-Newtonian flow models, many investigators are aiming on figuring out the solutions of these complex nonlinear flow equations.
Analysis of entropy optimization for sinusoidal wall motion of fourth-grade fluid with temperature-dependent viscosity
Published in Waves in Random and Complex Media, 2021
Muhammad Yousaf Rafiq, Zaheer Abbas
The research on non-Newtonian materials has gained special importance in recent industrial and technological processes. These substances are comprised in biotechnology, geophysics, petroleum, and chemical engineering [21–25]. All non-Newtonian materials depend on shear impacts that are not characterized by a single constitutive relationship. Therefore, the analyst suggests numerous non-Newtonian liquid models to explore the relationship between stress and rate of deformation. Among these differential-type non-Newtonian liquid models, the most generalized model is the fourth-grade model which simultaneously reflects most of the non-Newtonian flow possessions. One of the imperative attributes of fourth-grade liquid is the ability to show normal stress differences in simple shear flows, which leads to characteristic mechanisms such as die-swell or rod-climbing. Khan et al. [26] studied the consequence of chemical reaction on the peristaltic transportation of fourth grade fluid inside a curved channel. In this analysis, the authors found that concentration profile significantly reduces by increasing the impact of a chemical reaction and Schmidt number. The radiative aspects on the sinusoidal wall motion of fourth grade nanomaterial in a channel along with slip conditions were deliberated by Hayat et al. [27]. Recently, Rafiq et al. [28] deliberated the thermal transportation aspects on the peristaltically induced flow of fourth-grade liquid in a tapered channel. A survey of fourth-grade fluid is accessible [29,30]. Additionally, variable viscosity plays an imperative role in the problems of peristaltic movement due to its numerous biological and engineering applications. In general, the viscosity coefficient for real liquids is a function of temperature (see [31,32]). The temperature distribution in several thermal movement processes is never uniform in the flow field, i.e. high-temperature dissimilarities in the system can cause appreciably alterations in the liquid viscosity. So, it is greatly desirable to comprise the temperature-dependent viscosity in the thermal transportation procedures. The influence of temperature-dependent viscosity of the Rabinowitsch fluid propagating peristaltically past a channel was studied by Rajashekhar et al. [33] and distinguished an enhance in the momentum and temperature profiles as the amplitude oscillation was amplified. Divya et al. [34] scrutinized the aspects of temperature-dependent viscosity in the sinusoidal wall activity of a Casson liquid in a non-uniform channel. Recently, the variability in the temperature conductivity on the sinusoidal movement of Sutterby materials in a curved configuration was characterized by Hayat et al. [35]. He established in his conclusions that Irregularity is minimum for augmented radiation and thermal conductivity.