Appropriate Boundary Conditions in the Flow of Molten Polymers
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S. G. Hatzikiriakos
Abstract
There is considerable experimental evidence that the classical no-slip boundary condition of fluid mechanics is not always a valid assumption for the flow of high molecular weight molten polymers. In fact, molten polymers slip at solid surfaces when the wall shear stress exceeds a critical value. Moreover, there exists a second critical wall shear stress value at which a transition from a weak to a strong slip takes place. The later corresponds to the case of an almost plug flow and it is accompanied by pressure oscillations in the case of capillary flow generated by a constant-speed piston-driven capillary rheometer. The two modes of slip (weak and strong) are due to flow-induced chain detachment/desorption directly from the polymer/wall interface and to chain disentanglement of the polymer chains in the bulk from a monolayer of polymer chains adsorbed at the interface. In this work, the two physical mechanisms of slip are discussed and validated on the basis of suitably analyzed experimental data. Based on these two modes of slip, the slip phenomena observed during the capillary flow of polymers (mainly polyethylenes) are explained including the absence of pressure oscillations in the capillary flow of branched polyethylenes.
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Articles in the same Issue
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- Professor James Lindsay White 1938–2009
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- Effect of Clay on Thermal, Mechanical and Gas Barrier Properties of Biodegradable Poly(lactic acid)/Poly(butylene succinate) (PLA/PBS) Nanocomposites
- Thermo-mechanical Properties of Urea-based Pattern Molding Compounds for Investment Casting
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- Production and Characterization of PP/LDPE Blend Filament Yarns under Industrial Conditions
- Modelling Post-molding Warping
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- Appropriate Boundary Conditions in the Flow of Molten Polymers
- Multiscale Simulation of Injection Molding of Parts with Low Aspect Ratio Microfeatures
- PPS-News
- PPS News
- Seikei Kakou Abstracts
- Seikei-Kakou Abstracts
- Polímeros: Ciência e Tecnologia Abstracts
- Polímeros: Ciência e Tecnologia – Abstracts
Articles in the same Issue
- Contents
- Contents
- Editorial
- Professor James Lindsay White 1938–2009
- Regular Contributed Articles
- Effect of Clay on Thermal, Mechanical and Gas Barrier Properties of Biodegradable Poly(lactic acid)/Poly(butylene succinate) (PLA/PBS) Nanocomposites
- Thermo-mechanical Properties of Urea-based Pattern Molding Compounds for Investment Casting
- Erosion Wear Analysis of SiC Filled Glass-Epoxy Composites using Taguchi Technique
- Production and Characterization of PP/LDPE Blend Filament Yarns under Industrial Conditions
- Modelling Post-molding Warping
- Modelling Post-molding Warping
- Appropriate Boundary Conditions in the Flow of Molten Polymers
- Multiscale Simulation of Injection Molding of Parts with Low Aspect Ratio Microfeatures
- PPS-News
- PPS News
- Seikei Kakou Abstracts
- Seikei-Kakou Abstracts
- Polímeros: Ciência e Tecnologia Abstracts
- Polímeros: Ciência e Tecnologia – Abstracts