Modelling of Pore Collapse during Polymer Sintering: Viscoelastic Model with Enclosed Gas

Language
en
Document Type
Article
Issue Date
2021-05-05
First published
2021-04-24
Issue Year
2021
Authors
Wohlgemuth, Florian
Lellinger, Dirk
Alig, Ingo
Editor
Publisher
MDPI
Abstract

Frenkel’s model for the late stage of coalescence of viscous particles has been extended to describe pore collapse in a viscoelastic melt during polymer sintering. The shrinkage of a pore in a polymer melt driven by surface tension is extended by taking into account the effects of trapped gas and gas transport out of the pore. Viscoelasticity has been shown to have a considerable impact on the time scale of the coalescence process. In addition, gas diffusion modifies the coalescence dynamics. Based on a parameter study, different regimes for the pore collapse have been identified. At the beginning of pore collapse, surface tension is considerably stronger than gas pressure within the pore. In this time interval (surface-tension-driven regime), the pore shrinks even in the absence of gas diffusion through the matrix. In the absence of gas transport, the shrinkage dynamic slows down and stops when the surface tension balances the gas pressure in the pore. If gas transport out of the pore is possible, surface tension and gas pressure are balanced while the gas pressure slowly decreases (diffusion-controlled regime). The final phase of pore collapse, which occurs when the gas pressure within the pore decreases sufficiently, is controlled again by surface tension. The limitations of the model are discussed. To analyze the interplay between different mechanisms and process steps during selective laser sintering, the respective time scales are compared using experimental data.

Journal Title
Materials
Volume
14
Issue
9
Citation
Materials 14.9 (2021): 2182. <https://www.mdpi.com/1996-1944/14/9/2182>
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