Semicrystalline polymers are an attractive feedstock choice for material extrusion (MatEx)-based three-dimensional printing processes. However, the printed parts often exhibit poor mechanical properties due to weak interlayer strength thereby limiting the widespread adoption of MatEx. Improved interlayer strength in the printed parts can be achieved through a combination of process parameter selection and material modification but a physics-based understanding of the underlying mechanism is not well understood. Furthermore, the localized thermal history experienced by the prints can significantly influence the strength of the interlayer welds. In this work, a combined experimental and modeling approach has been employed to highlight the relative impact of rheology, non-isothermal crystallization kinetics, and print geometry on the interlayer strength of printed parts of two semicrystalline polymers, namely, polylactic acid (PLA) and polypropylene (PP). Specifically, the print properties have been characterized as a function of print temperature and print speed. In the case of single road width wall (SRWW) PLA prints, the total crystalline fraction increases due to the broadening of the crystallization window at higher print temperatures and lower print speeds. The results are substantiated by the constitutive modeling results that account for the effects of quiescent crystallization. However, SRWW PP prints display a reduction in the interlayer properties with temperature likely due to significant flow-induced crystallization effects, as suggested by the model. Interestingly, in the case of multilayer PP prints, the repeated heating/cooling cycles encountered during printing counteracts the flow-induced effects leading to an increase in mechanical properties with print temperature consistent with SRWW PLA prints.
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December 2022
Research Article|
December 07 2022
Rheology, crystallization, and process conditions: The effect on interlayer properties in three-dimensional printing
Special Collection:
Advanced Rheology of Complex Fluids for Next-Generation Technologies
Arit Das
;
Arit Das
(Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Visualization, Writing – original draft)
1
Department of Chemical Engineering, Virginia Polytechnic and State University
, Blacksburg, Virginia 24061, USA
2
Macromolecules Innovation Institute, Virginia Polytechnic and State University
, Blacksburg, Virginia 24061, USA
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Jocelyn A. Riet
;
Jocelyn A. Riet
a)
(Data curation, Investigation, Methodology, Validation, Visualization)
1
Department of Chemical Engineering, Virginia Polytechnic and State University
, Blacksburg, Virginia 24061, USA
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Michael J. Bortner
;
Michael J. Bortner
b)
(Conceptualization, Data curation, Funding acquisition, Project administration, Resources, Supervision, Writing – review & editing)
1
Department of Chemical Engineering, Virginia Polytechnic and State University
, Blacksburg, Virginia 24061, USA
2
Macromolecules Innovation Institute, Virginia Polytechnic and State University
, Blacksburg, Virginia 24061, USA
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Claire McIlroy
Claire McIlroy
b)
(Conceptualization, Data curation, Formal analysis, Investigation, Project administration, Resources, Software, Writing – original draft, Writing – review & editing)
3
School of Mathematics and Physics, University of Lincoln
, Lincoln LN6 7TS, United Kingdom
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a)
Current address: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada.
Note: This paper is part of the special topic, Advanced Rheology of Complex Fluids for Next-Generation Technologies.
Physics of Fluids 34, 123108 (2022)
Article history
Received:
September 29 2022
Accepted:
November 18 2022
Citation
Arit Das, Jocelyn A. Riet, Michael J. Bortner, Claire McIlroy; Rheology, crystallization, and process conditions: The effect on interlayer properties in three-dimensional printing. Physics of Fluids 1 December 2022; 34 (12): 123108. https://doi.org/10.1063/5.0128660
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