Flow‐Induced Orientation and Structure Formation

Keller, A.; Kolnaar, Hans W. H.

doi:10.1002/9783527603978.mst0210

Cited by 132 publications

(241 citation statements)

References 108 publications

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“…The concentration of shish increased with increasing hauloff speeds and at the highest haul-off speeds (highest density of shish) manifest as distinct scattering intensity on the equator at the same time as the meridional scattering from the lamellae stacks. The crystallization process down the tape-line was interpreted using the classical coil-stretch model for entangled polymer melts proposed by Keller [4].…”

Section: Discussionmentioning

confidence: 99%

“…This theory suggested that at a critical strain rate, polymer chains undergo a shape transition from a random coil configuration to a fully extended chain. Keller [4] went on to show how the coil-stretch transition could be applied to entangled polymer melts and was central in developing his well-known model of shish-kebab morphology.…”

Section: Crystallization Processes In the Extruded Tapementioning

confidence: 99%

“…Here, the chain extension via flow or elongation processes, form the shish and at a later time the coiled chains then go on to form the crystalline outgrowths or kebabs [4,56]. This model is now widely accepted as the process by which crystallization in entangled polymer melts occurs under all types of flow.…”

Section: Crystallization Processes In the Extruded Tapementioning

confidence: 99%

“…The type of nucleation and subsequent crystallization is profoundly influenced by flow due to the alignment or orientation of the molecular chains [2][3][4][5]. The route to crystallization during flow is generally accepted to be via the formation of 'shishkebab' morphology [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

Heeley

Gough

Hughes

et al. 2013

Polymer

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Ray scattering (SAXS). AbstractThe in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness (~50 Å) and bulk crystallinity (~20%), were low for all processing conditions investigated, which is attributed to the significant shortchain branching in the polymer acting as point defects limiting lamellae crystal growth.2

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Section: Discussionmentioning

confidence: 99%

Section: Crystallization Processes In the Extruded Tapementioning

confidence: 99%

Section: Crystallization Processes In the Extruded Tapementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

Heeley

Gough

Hughes

et al. 2013

Polymer

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“…1 The combination of microstructure and coupling to flow crucially affects the processing and final materials properties. 2,3 Due to the relatively long structural relaxation times of polymers as compared to low molecular weight liquids, they show memory effects on experimentally accessible time scales, and conventional flow conditions result in significant distortion of their structure. As a consequence of chain orientation and stretch, the polymers crystallize more easily in flow than in quiescent conditions.…”

Section: Introductionmentioning

confidence: 99%

Crystal shapes and crystallization in continuum modeling

Hütter

Armstrong

2004

Physics of Fluids

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A crystallization model appropriate for application in continuum modeling of complex processes is presented. As an extension to the previously developed Schneider equations [W. Schneider, A. Köppel, and J. Berger, "Non-isothermal crystallization of polymers," Int. Polym. Proc. 2, 151 (1988)], the model presented here allows one to account for the growth of crystals of various shapes and to distinguish between one-, two-, and three-dimensional growth, e.g., between rod-like, plate-like, and sphere-like growth. It is explained how a priori knowledge of the shape and growth processes is to be built into the model in a compact form and how experimental data can be used in conjunction with the dynamic model to determine its growth parameters. The model is capable of treating transient processing conditions and permits their straightforward implementation. By using thermodynamic methods, the intimate relation between the crystal shape and the driving forces for phase change is highlighted. All these capabilities and the versatility of the method are made possible by the consistent use of four structural variables to describe the crystal shape and number density, irrespective of the growth dimensionality.

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