On flow layer uniformity in the co-extrusion of polymer multilayer film

Guo Chiuan Tzeng, Ren-Haw Chen

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

In the multilayer co-extrusion process, two or more materials are simultaneously brought together and layered in a single extrusion process. When co-extruding two polymers with different rheological properties, uniformity control of the flow layer at and downstream of the confluence is vital for the quality of multilayered film products. This work aimed to investigate the effects of viscosity and elasticity of the co-extruding polymers on the layer uniformity at the confluence. We conducted a PC/PMMA/PC three-layer film co-extrusion experiment to observe the flow of polymer melts at the confluence in the die. The thickness variation of each layer along the flow was recorded through a viewing window structured on the die wall using a camera. In addition, the flow and stress field analyses of PC/PMMA/PC co-extrusion were performed using POLYFLOW software. The research results demonstrated that oscillation of flow velocity in machine direction along the PC/PMMA interface accompanying a wavy distribution of layer thickness along the flow may occur due to the differences of viscosity and elasticity between the PC and PMMA. Although slipping may occur at the PC/PMMA interface, which reduces the shear stress between the PC and the PMMA layer boundaries, the shear stress distribution crossing the PC/PMMA interface is not continuous. The imbalance of the shear stresses along the adjacent PC and PMMA boundaries expands with the extrusion rate, which can cause the interface to distort. To avoid the occurrence of interfacial instability, the length of die channel downstream the confluence must be shortened as much as possible, and the extrusion rate must be lowered.

Original languageEnglish
Title of host publicationAdvances in Materials and Processing Technologies XVI
PublisherTrans Tech Publications
Pages381-387
Number of pages7
ISBN (Print)9783038350972
DOIs
StatePublished - 1 Jan 2014
Event16th International Conference on Advanced Materials and Processing Technologies, AMPT 2013 - Taipei, Taiwan
Duration: 22 Sep 201326 Sep 2013

Publication series

NameAdvanced Materials Research
Volume939
ISSN (Print)1022-6680

Conference

Conference16th International Conference on Advanced Materials and Processing Technologies, AMPT 2013
CountryTaiwan
CityTaipei
Period22/09/1326/09/13

Keywords

  • Co-extrusion
  • Layer uniformity
  • Multilayer film

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