Influence of the viscosity of polymer melts on the coextrusion process based on wall slip conditions

Xiaozhen Deng; Tianrong Chen; Bing Xiao; Zhong Ren; Gang Tang; Fang Xu; Xiaoxiao Yan

doi:10.1515/ipp-2024-0104

Article

Influence of the viscosity of polymer melts on the coextrusion process based on wall slip conditions

Xiaozhen Deng , Tianrong Chen , Bing Xiao , Zhong Ren , Gang Tang , Fang Xu and Xiaoxiao Yan

Published/Copyright: February 12, 2025

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From the journal International Polymer Processing Volume 40 Issue 1

Abstract

Three-dimensional viscoelastic flow numerical models for the polymer coextrusion process were established on the basis of two different wall conditions and solved via finite element methods. The influence of polymer melt viscosity on the coextrusion process was investigated by analyzing die swell, melt interlayer interface stability and flow field distribution under two different wall slip conditions, namely, sticky adhesive condition and fully slip non adhesive condition. The results indicate that in the traditional coextrusion process with sticky adhesive condition, the die swell, interface stability and flow field distribution change with the melt viscosity, but the effects of the shell melt viscosity differ from those of the core melt viscosity. The die swell, interface offset degree and radial flow strength (orthogonal to the flow direction) increase with increasing shell melt viscosity and decrease with increasing core melt viscosity. The die pressure drop, shear rate and first normal stress difference increase with increasing shell or core melt viscosity, but the influence of the shell melt viscosity is much greater than that of the core melt viscosity. In the gas-assisted coextrusion process with fully slip non adhesive condition, the die swell, interface stability and flow field distribution are not affected by the viscosity of both polymer melts which means that the flow behavior in the coextrusion channels is independent of the polymer viscosity. There is no die swell or interface deviation phenomenon, nor any melt radial flow. The die pressure drop, shear rate and first normal stress difference are close to zero, except in the close vicinity of the die inlet. This approach not only ensures product quality but also solves the problem of material selection for polymer coextruded products. In addition, the goal of energy conservation and consumption reduction has been achieved, and the energy savings and consumption reduction effects are particularly significant for high-viscosity melts.

Keywords: polymer melt viscosity; coextrusion process; wall slip; die swell; gas-assisted coextrusion

Corresponding authors: Bing Xiao, Jiangxi Provincial Key Laboratory of Precision Drive and Equipment, School of Mechanical Engineering, Nanchang Institute of Technology, Nanchang 330099, China, E-mail: hubeixiao@163.com; and Zhong Ren, Jiangxi Provincial Key Laboratory of Advanced Electronic Materials and Devices, Jiangxi Science and Technology Normal University, Nanchang 330038, China, E-mail: renzhong0921@163.com

Acknowledgements

This work was financially supported by the Key Research and Development Program Project of Jiangxi Province (20243BBI91011), the National Natural Science Foundation of China (No. 62165006), the Science Funding in the Education Department of Jiangxi province (No. GJJ190950), the Open Project Fund of Key Laboratory for Optoelectronics and Communication of Jiangxi Province (No. 20202OEC001), Jiangxi Province Key Project of Natural and Science Fund (No. 20224ACB202004) and 2023 Jiangxi Province Ganpo Juncai Support Plan-High level and High skilled Leading Talent Training Project.

Research ethics: Not applicable.
Informed consent: Informed consent was obtained from all individuals included in this study, or their legal guardians or wards.
Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Use of Large Language Models, AI and Machine Learning Tools: None declared.
Conflict of interest: The authors state no conflict of interest.
Research funding: 1. The Key Research and Development Program Project of Jiangxi Province (No. 20243BBI91011); 2.The National Natural Science Foundation of China (No. 62165006); 3. The Science Funding in the Education Department of Jiangxi province (No. GJJ190950); 4. The Open Project Fund of Key Laboratory for Optoelectronics and Communication of Jiangxi Province (No. 20202OEC001); 5. Jiangxi Province Key Project of Natural and Science Fund (No. 20224ACB202004); 6. 2023 Jiangxi Province Ganpo Juncai Support Plan-High level and High skilled Leading Talent Training Project.
Data availability: The raw data can be obtained on request from the corresponding author.

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Received: 2024-08-11

Accepted: 2024-12-13

Published Online: 2025-02-12

Published in Print: 2025-03-26

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Articles in the same Issue

https://doi.org/10.1515/ipp-2024-0104

Keywords for this article

polymer melt viscosity; coextrusion process; wall slip; die swell; gas-assisted coextrusion