Convective linear stability analysis of two-layer coextrusion flow for molten polymers

Abstract : The interface instability of the coextrusion flow of a polyethylene and a polystyrene is studied both experimentally and theoretically in a slit geometry. For prototype industrial conditions, we have found a stable/unstable transition which bounds the occurrence of stable/unstable sheets at die exit. By investigating a large range of processing conditions, we have shown that this transition is controlled by both temperature and flow rate ratios. Close to the transition, we used a transparent die to measure spatial amplification of different controlled perturbations at die inlet and pointed out the convective nature of the instability which exhibits a dominant mode (for which the instability is the most severe). We have then found that a convective stability analysis, using the White–Metzner constitutive equation, is able to account for the spatial amplification rate experimentally measured on controlled perturbation experiments. By considering that the instability is controlled by its dominant mode, we performed a convective stability analysis for all studied prototype industrial conditions and showed that such an analysis is able to forecast the occurrence of defects at die exit.
Document type :
Journal articles
Complete list of metadatas

https://hal.archives-ouvertes.fr/hal-00015338
Contributor : Katy Remy <>
Submitted on : Tuesday, December 6, 2005 - 2:32:05 PM
Last modification on : Monday, November 12, 2018 - 10:59:37 AM

Identifiers

Citation

Rudy Valette, Patrice Laure, Yves Demay, Jean-François Agassant. Convective linear stability analysis of two-layer coextrusion flow for molten polymers. Journal of Non-Newtonian Fluid Mechanics, Elsevier, 2004, 121 (1), pp.41-53. ⟨10.1016/j.jnnfm.2004.04.002⟩. ⟨hal-00015338⟩

Share

Metrics

Record views

219