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Sattler R, Zhang R, Gupta G, Du M, Runge PM, Altenbach H, Androsch R, Beiner M. Influence of Crystallization Kinetics and Flow Behavior on Structural Inhomogeneities in 3D-Printed Parts Made from Semi-Crystalline Polymers. Macromolecules 2024; 57:3066-3080. [PMID: 38616808 PMCID: PMC11008537 DOI: 10.1021/acs.macromol.3c01940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 03/01/2024] [Accepted: 03/05/2024] [Indexed: 04/16/2024]
Abstract
We report the results of a study focusing on the influence of crystallization kinetics and flow behavior on structural inhomogeneities in 3D-printed parts made from polyamide 12 (PA12) and poly(lactic acid) (PLA) by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), fast scanning calorimetry (FSC), and wide-angle X-ray diffraction (WAXD). Temperature-dependent WAXD measurements on the neat PLA filament reveal that PLA forms a single orthorhombic α phase during slow cooling and subsequent 2nd heating. The PA12 filament shows a well pronounced polymorphism with a reversible solid-solid phase transition between the (pseudo)hexagonal γ phase near room temperature and the monoclinic α' phase above the Brill transition temperature TB = 140 °C. The influence of the print bed temperature Tb on structure formation, polymorphic state, and degree of crystallinity χc of the 3D-printed parts is investigated by height and depth-dependent WAXD scans and compared with that of 3D-printed single layers, used as a reference. It is found that the heat transferred from successive layers has a strong influence on the polymorphic state of PA12 since a superimposed mixture of γ and α phases is present in the 3D-printed parts. In the case of PLA, a single α phase is formed. The print bed temperature has, in comparison to PA12, a major influence on the degree of crystallinity χc and thus the homogeneity of the 3D-printed parts, especially close to the print bed. By comparing the obtained results from WAXD, DMA, DSC, and FSC measurements with relevant printing times, guidelines for 3D-printed parts with a homogeneous structure are derived.
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Affiliation(s)
- Rene Sattler
- Fraunhofer
Institute for Microstructure of Materials and Systems IMWS, Walter-Hülse-Str. 1, DE-06120 Halle (Saale), Germany
- Faculty
of Natural Sciences II, Martin-Luther-University
Halle-Wittenberg, Heinrich-Damerow-Str.
4, D-06120 Halle
(Saale), Germany
| | - Rui Zhang
- Interdisciplinary
Center for Transfer-Oriented Research in Natural Sciences, Martin-Luther-University Halle-Wittenberg, Universitätsplatz 10, D-06120 Halle (Saale), Germany
| | - Gaurav Gupta
- Fraunhofer
Institute for Microstructure of Materials and Systems IMWS, Walter-Hülse-Str. 1, DE-06120 Halle (Saale), Germany
- Faculty
of Natural Sciences II, Martin-Luther-University
Halle-Wittenberg, Heinrich-Damerow-Str.
4, D-06120 Halle
(Saale), Germany
| | - Mengxue Du
- Interdisciplinary
Center for Transfer-Oriented Research in Natural Sciences, Martin-Luther-University Halle-Wittenberg, Universitätsplatz 10, D-06120 Halle (Saale), Germany
| | - Paul-Maximilian Runge
- Institute
of Mechanics, Otto-von-Guericke-University
Magdeburg, Universitätsplatz
2, D-39106 Magdeburg, Germany
| | - Holm Altenbach
- Institute
of Mechanics, Otto-von-Guericke-University
Magdeburg, Universitätsplatz
2, D-39106 Magdeburg, Germany
| | - René Androsch
- Interdisciplinary
Center for Transfer-Oriented Research in Natural Sciences, Martin-Luther-University Halle-Wittenberg, Universitätsplatz 10, D-06120 Halle (Saale), Germany
| | - Mario Beiner
- Fraunhofer
Institute for Microstructure of Materials and Systems IMWS, Walter-Hülse-Str. 1, DE-06120 Halle (Saale), Germany
- Faculty
of Natural Sciences II, Martin-Luther-University
Halle-Wittenberg, Heinrich-Damerow-Str.
4, D-06120 Halle
(Saale), Germany
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Samadi MR, Afshari M, Nasehi M, Hardani H. Investigating the mechanical properties and microstructure of the weld joint obtained by laser welding of
PA12
/
CNT
nanocomposites. POLYM ENG SCI 2023. [DOI: 10.1002/pen.26313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
Affiliation(s)
- Mohammad Reza Samadi
- Faculty of Mechanical Engineering Technical and Vocational University (TVU) Tehran Iran
| | - Mahmoud Afshari
- Department of Mechanical Engineering Amirkabir University of Technology Tehran Iran
| | | | - Hatam Hardani
- Department of Mechanical Engineering, Ahvaz Branch Islamic Azad University Ahvaz Iran
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Molecular Pathways for Polymer Degradation during Conventional Processing, Additive Manufacturing, and Mechanical Recycling. Molecules 2023; 28:molecules28052344. [PMID: 36903589 PMCID: PMC10004996 DOI: 10.3390/molecules28052344] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 02/20/2023] [Accepted: 02/28/2023] [Indexed: 03/06/2023] Open
Abstract
The assessment of the extent of degradation of polymer molecules during processing via conventional (e.g., extrusion and injection molding) and emerging (e.g., additive manufacturing; AM) techniques is important for both the final polymer material performance with respect to technical specifications and the material circularity. In this contribution, the most relevant (thermal, thermo-mechanical, thermal-oxidative, hydrolysis) degradation mechanisms of polymer materials during processing are discussed, addressing conventional extrusion-based manufacturing, including mechanical recycling, and AM. An overview is given of the most important experimental characterization techniques, and it is explained how these can be connected with modeling tools. Case studies are incorporated, dealing with polyesters, styrene-based materials, and polyolefins, as well as the typical AM polymers. Guidelines are formulated in view of a better molecular scale driven degradation control.
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Vaes D, Coppens M, Goderis B, Zoetelief W, Van Puyvelde P. The Extent of Interlayer Bond Strength during Fused Filament Fabrication of Nylon Copolymers: An Interplay between Thermal History and Crystalline Morphology. Polymers (Basel) 2021; 13:polym13162677. [PMID: 34451217 PMCID: PMC8401508 DOI: 10.3390/polym13162677] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 11/16/2022] Open
Abstract
One of the main drawbacks of Fused Filament Fabrication is the often-inadequate mechanical performance of printed parts due to a lack of sufficient interlayer bonding between successively deposited layers. The phenomenon of interlayer bonding becomes especially complex for semi-crystalline polymers, as, besides the extremely non-isothermal temperature history experienced by the extruded layers, the ongoing crystallization process will greatly complicate its analysis. This work attempts to elucidate a possible relation between the degree of crystallinity attained during printing by mimicking the experienced thermal history with Fast Scanning Chip Calorimetry, the extent of interlayer bonding by performing trouser tear fracture tests on printed specimens, and the resulting crystalline morphology at the weld interface through visualization with polarized light microscopy. Different printing conditions are defined, which all vary in terms of processing parameters or feedstock molecular weight. The concept of an equivalent isothermal weld time is utilized to validate whether an amorphous healing theory is capable of explaining the observed trends in weld strength. Interlayer bond strength was found to be positively impacted by an increased liquefier temperature and reduced feedstock molecular weight as predicted by the weld time. An increase in liquefier temperature of 40 °C brings about a tear energy value that is three to four times higher. The print speed was found to have a negligible effect. An elevated build plate temperature will lead to an increased degree of crystallinity, generally resulting in about a 1.5 times larger crystalline fraction compared to when printing occurs at a lower build plate temperature, as well as larger spherulites attained during printing, as it allows crystallization to occur at higher temperatures. Due to slower crystal growth, a lower tie chain density in the amorphous interlamellar regions is believed to be created, which will negatively impact interlayer bond strength.
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Affiliation(s)
- Dries Vaes
- Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200J Box 2424, 3001 Leuven, Belgium; (D.V.); (M.C.)
| | - Margot Coppens
- Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200J Box 2424, 3001 Leuven, Belgium; (D.V.); (M.C.)
| | - Bart Goderis
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F Box 2404, 3001 Leuven, Belgium;
| | - Wim Zoetelief
- DSM Additive Manufacturing, Urmonderbaan 22, 6167 RD Geleen, The Netherlands;
| | - Peter Van Puyvelde
- Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200J Box 2424, 3001 Leuven, Belgium; (D.V.); (M.C.)
- Correspondence:
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Liparoti S, Sofia D, Romano A, Marra F, Pantani R. Fused Filament Deposition of PLA: The Role of Interlayer Adhesion in the Mechanical Performances. Polymers (Basel) 2021; 13:399. [PMID: 33513767 PMCID: PMC7865617 DOI: 10.3390/polym13030399] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 11/21/2022] Open
Abstract
A set of criteria to enhance mechanical performances of standard specimens (Type V, ANSI D368) made of polylactic acid (PLA) were proposed. Fused PLA deposition was conducted with nozzle temperature ranging from 180 to 230 °C and deposition plate temperature ranging from 70 to 110 °C. Optical microscopy, elastic modulus analysis and density measurement allowed emphasizing the effect of temperature field, also measured during the process, on the morphology and the mechanical characteristics of the specimen. Atomic force microscopy revealed a morphology typical of amorphous samples with globular structures. Poor interlayer adhesion was detected in the part of the specimen located at larger distance from the deposition plate, showing an elastic modulus lower than those measured in the central part (220 MPa vs. 500 MPa). The specimen crystallinity degree was below 3%. The molecular weight between entanglements was adopted as a measure of the interlayer molecular diffusion. A successful diffusion and re-entanglement of the polymer melt at the interface was the key to improving mechanical performance. A mathematical model describing the transient heat transfer during the fused PLA deposition and accounting for solidification and the nonisothermal crystallization kinetics was introduced. Simulated temperature evolutions were consistent with the experimental ones. They were related to the mechanical performances, the morphology, and the molecular weight between entanglements of the parts.
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Affiliation(s)
| | | | | | - Francesco Marra
- Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fiscian, SA, Italy; (S.L.); (D.S.); (A.R.); (R.P.)
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