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Polymers 2019, 11(3), 432; https://doi.org/10.3390/polym11030432

Online Rheometry Investigation of Flow/Slip Behavior of Powder Injection Molding Feedstocks

1
Dept. of Production Engineering, Faculty of Technology, Tomas Bata University in Zlin, nám. T. G. Masaryka 5555, 760 01 Zlín, Czech Republic
2
Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Trida T. Bati 5678, 760 01 Zlín, Czech Republic
*
Author to whom correspondence should be addressed.
Received: 10 January 2019 / Revised: 24 February 2019 / Accepted: 27 February 2019 / Published: 6 March 2019
(This article belongs to the Special Issue Materials and Methods for New Technologies in Polymer Processing)
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Abstract

Wall slip in the flow of powder injection molding (PIM) compounds can be the cause of unrealistically low viscosity values, and can lead to a failure of flow simulation approaches. Regardless of its importance, it has been considered only scarcely in the rheological models applied to PIM materials. In this paper, an online extrusion rheometer equipped with rectangular slit dies was used to evaluate the slip velocity of commercial as well as in-house-prepared PIM feedstocks based on metallic and ceramic powders at close-to-processing conditions. The tested slit dies varied in their dimensions and surface roughness. The wall-slip effect was quantified using the Mooney analysis of slip velocities. The smaller gap height (1 mm) supported the wall-slip effect. It was shown that both the binder composition and the powder characteristic affect slip velocity. Slip velocity can be reduced by tailoring a powder particle size distribution towards smaller particle fractions. The thickness of the polymer layer formed at the channel wall is higher for water-soluble feedstocks, while in the case of the catalytic polyacetal feedstocks the effect of surface roughness was manifested through lower viscosity at smooth surfaces. View Full-Text
Keywords: powder injection molding; feedstock; online rheometer; wall slip; slit die; surface roughness powder injection molding; feedstock; online rheometer; wall slip; slit die; surface roughness
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Sanetrnik, D.; Hausnerova, B.; Pata, V. Online Rheometry Investigation of Flow/Slip Behavior of Powder Injection Molding Feedstocks. Polymers 2019, 11, 432.

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