Flow Characteristics of Polymer Melt for Die Shapes for the Extrusion of Catheter Tubing

AbstractThe conventional theoretical method to calculate deformations and stress states is only limited to a few cases of simple extrusion dies due to a number of assumptions and simplifications. A coupled thermal-structural modelling framework incorporating finite element method is thus developed and implemented to determine the mechanical performances of the complicated spiral mandrel die, which has a complex geometrical feature of spiral grooves and is exposed to severe conditions of thermal load and high pressure. The steady-state thermal analysis is carried out by mapping the temperature load on the flow channel from previously simulated flow characteristics of polymer melt. The structural analysis takes inputs from both thermal analysis and previously simulated pressure on polymer melt. Both the temperature and pressure loads on flow channel are transferred via the Smart Bucket Surface mapping algorithm. The mechanical properties of the spiral mandrel die are evaluated by analysing the deformation and stress distribution. The experimental validation is conducted to demonstrate the effectiveness of the numerical model. The effects of both structure parameters of the spiral mandrel and processing parameters upon the maximum stress in the die body and the maximum pressure induced deformation at the die orifice are investigated.

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A study of novel viscous dissipation measurement for polymer melts in microchannels

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes1942 ◽

2010 ◽

Vol 224 (9) ◽

pp. 2027-2035 ◽

Cited By ~ 1

Author(s):

B Xu ◽

M Wang ◽

T Yu ◽

D Zhao

Keyword(s):

Viscous Dissipation ◽

High Density Polyethylene ◽

Polymer Melts ◽

Flow Characteristics ◽

Rheological Behaviour ◽

Polymer Melt ◽

Experimental Results ◽

Maximum Temperature ◽

Number Of Factors ◽

Different Temperatures

Studies on the rheological behaviour of polymer melts, flowing through microchannels, are complicated because a large number of factors affect the melt viscosity. One such factor, viscous dissipation, is investigated in the current work through a novel experimental technique that is used in determining the viscous dissipation of a polymer melt flowing through microchannels. Relative tests are conducted using melts of high-density polyethylene (HDPE) extruded through several capillary dies at different temperatures. Experimental results indicate that the temperature rises due to viscous dissipation increase with increasing shear rate. In addition, simulations considering viscous dissipation are carried out. The comparison of the experimental results with those predicted from the simulations at different melt temperatures indicates that the maximum temperature rise deviation is about 15 per cent. Therefore, the measurement method of viscous dissipation is available, which is helpful to better understand the flow characteristics of microchannels.

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Effect of the entry cone angle of the spinneret hole on the flow characteristics of the polymer melt

Fibre Chemistry ◽

10.1007/bf00553303 ◽

1987 ◽

Vol 18 (3) ◽

pp. 213-216 ◽

Cited By ~ 2

Author(s):

V. P. Pervadchuk ◽

I. O. Glot ◽

V. I. Yankov ◽

A. S. Borisov ◽

Yu. A. Vinogradov

Keyword(s):

Cone Angle ◽

Flow Characteristics ◽

Polymer Melt ◽

Spinneret Hole

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Control-Oriented Modeling of an Injection Molding Machine Including the Fill-to-Pack Transition

10.1115/imece2000-2321 ◽

2000 ◽

Author(s):

Danian Zheng ◽

Andrew Alleyne ◽

Heather Havlicsek

Keyword(s):

Injection Molding ◽

Controller Design ◽

Flow Characteristics ◽

Polymer Melt ◽

Hydraulic Actuator ◽

Molding Machine ◽

Injection Molding Machine ◽

Digitally Controlled ◽

Engineering Models ◽

Injection Cycle

Abstract In this paper the modeling of a typical injection cycle for an injection molding machine (IMM) is examined. Both the mold filling and mold packing phases of the cycle are examined along with a critical fill-to-pack transition. The novelty in this modeling work is that the non-linear model considers both the machine hydraulic actuator and polymer flow characteristics in extensive detail. The resulting model will provide simulation capabilities to facilitate machine controller design; however the actual controller is not the focus of the current work. The modeling is based on (a) the characteristics of digitally controlled electrohydraulic valves, (b) the dynamics of the hydraulic actuator ram system, and (c) the gross polymer melt behavior determined from simple polymer engineering models. The simulation model is validated against experimental data and demonstrates the availability of a relatively accurate system model for full cycle control of this electrohydraulic system.

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Numerical study of polymer melt flow in a three-dimensional sudden expansion: viscous dissipation effects

Journal of Polymer Engineering ◽

10.1515/polyeng-2013-0273 ◽

2014 ◽

Vol 34 (8) ◽

pp. 755-764

Author(s):

Mustafa Tutar ◽

Ali Karakus

Keyword(s):

Viscous Dissipation ◽

Stokes Equations ◽

Numerical Study ◽

Flow Behavior ◽

Flow Analysis ◽

Three Dimensional ◽

Flow Characteristics ◽

Polymer Melt ◽

Sudden Expansion ◽

Melt Flow

Abstract This numerical paper presents the effects of viscous dissipation on both hydrodynamic flow behavior and thermal flow characteristics of fluid included in rheological polymer flow analysis. The shear rate dependence of the viscosity is modeled using a modified form of the Cross constitutive equation, while the density changes are modeled using the modified Tait state of equation. The Navier-Stokes equations are solved in a sequential, decoupled manner with energy conservation equations using a finite volume method based fluid flow solver. Hydrodynamic and thermal boundary layer developments in an asymmetric sudden expansion for different velocity and melt flow injection temperature boundary and geometry conditions are determined under the influence of viscous dissipation effects and the results are compared with each other to measure the relative effects of viscous dissipation on the interactions of these layers for a commercial polymer melt flow, namely polypropylene (PP). The numerical results demonstrate that proposed mathematical and numerical formulations for viscosity and density variations including viscous heating terms lead to more accurate representation of the polymer melt flow and heat transfer phenomena in plane channels or mold cavity associated with a sudden expansion.

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Polymer Morphology Revealed by Staining Techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100098204 ◽

1981 ◽

Vol 39 ◽

pp. 340-341

Author(s):

A. C. Reimschuessel ◽

V. Kramer

Keyword(s):

Polymer Melt ◽

Nylon 6 ◽

Morphological Features ◽

Negative Staining ◽

Polymer Morphology ◽

Crystallizable Polymer ◽

Staining Techniques ◽

Long Chain

Staining techniques can be used for either the identification of different polymers or for the differentiation of specific morphological domains within a given polymer. To reveal morphological features in nylon 6, we choose a technique based upon diffusion of the staining agent into accessible regions of the polymer.When a crystallizable polymer - such as nylon 6 - is cooled from the melt, lamellae form by chainfolding of the crystallizing long chain macromolecules. The regions between adjacent lamellae represent the less ordered amorphous domains into which stain can diffuse. In this process the lamellae will be “outlined” by the dense stain, giving rise to contrast comparable to that obtained by “negative” staining techniques.If the cooling of the polymer melt proceeds relatively slowly - as in molding operations - the lamellae are usually arranged in a radial manner. This morphology is referred to as spherulitic.

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