Rheology of 3D Printing

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Physics and Theory".

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 17961

Special Issue Editor


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Guest Editor
POLYMAT and Polymer Science and Technology Department, Faculty of Chemistry, University of the Basque Country UPV/EHU, 20018 San Sebastian, Spain
Interests: rheological properties; linear and non-linear dynamic viscoelasticity; elongational flow; PVT measurements; polymer characterization and processing; copolymers; polymer blends; polymer nanocomposites; adhesives; coatings and gels
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Special Issue Information

Dear Colleagues,

In the last decade, additive manufacturing (AM), also generally known as 3D printing, is gaining ground because AM allows the construction of customized objects with high geometric complexity. Polymer melts are mostly used in 3D printing, leading to significant reductions in both time and manufacturing costs. The implications of rheology in this disruptive method of polymer processing are even more relevant than in well-known and investigated injection moulding and extrusion moulding methods. However, the number of quality papers about the subject is limited so far.

A basic requirement of AM is finding the optimal extrusion flow conditions to match the velocity at the exit of the nozzle with the printing velocity. This is related to the viscosity and elasticity of the polymer melt, which in turn depend on the molecular parameters, the temperature, and the geometry of the nozzle.  The viscoelastic behavior of the melt during cooling when deposited on the bed is also crucial because welding between layers, which determines the mechanical performance of the printed object, is closely related to viscoelasticity.

Studies on shear/elongational viscosity and extrudate swell, under conditions similar to those of 3D printing, as well as investigations on viscoelasticity and its correlation with interlayer adhesion, are welcome in this Special Issue. Theoretical and experimental works are also within the scope of this Special Issue.

Prof. emer. Antxon Santamaria
Guest Editor

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Keywords

  • Additive manufacturing
  • Extrusion flow
  • Shear/Elongational viscosity
  • Viscoelasticity
  • Welding

Published Papers (4 papers)

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Research

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20 pages, 5733 KiB  
Article
Print Velocity Effects on Strain-Rate Sensitivity of Acrylonitrile-Butadiene-Styrene Using Material Extrusion Additive Manufacturing
by Wilco M. H. Verbeeten, Rob J. Arnold-Bik and Miriam Lorenzo-Bañuelos
Polymers 2021, 13(1), 149; https://doi.org/10.3390/polym13010149 - 01 Jan 2021
Cited by 9 | Viewed by 2594
Abstract
The strain-rate sensitivity of the yield stress for Acrylonitrile-Butadiene-Styrene (ABS) tensile samples processed via material extrusion additive manufacturing (ME-AM) was investigated. Such specimens show molecular orientation and interstitial voids that affect the mechanical properties. Apparent densities were measured to compensate for the interstitial [...] Read more.
The strain-rate sensitivity of the yield stress for Acrylonitrile-Butadiene-Styrene (ABS) tensile samples processed via material extrusion additive manufacturing (ME-AM) was investigated. Such specimens show molecular orientation and interstitial voids that affect the mechanical properties. Apparent densities were measured to compensate for the interstitial voids. Three different printing speeds were used to generate ME-AM tensile test samples with different molecular orientation. Printing velocities influenced molecular orientation and stretch, as determined from thermal shrinkage measurements. Likewise, infill velocity affected the strain-rate dependence of the yield stress. The ABS material manifests thermorheollogically simple behavior that can correctly be described by an Eyring flow rule. The changing activation volume, as a result of a varying print velocity, scales linearly with the molecular orientation, as captured in an estimated processing-induced pre-strain. Therefore, it is suggested that ME-AM processed ABS shows a deformation-dependent activation volume. This paper can be seen as initial work that can help to improve quantitative predictive numerical tools for ME-AM, taking into account the effects that the processing step has on the mechanical properties. Full article
(This article belongs to the Special Issue Rheology of 3D Printing)
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17 pages, 4592 KiB  
Article
How Is Rheology Involved in 3D Printing of Phase-Separated PVC-Acrylate Copolymers Obtained by Free Radical Polymerization
by Mario Iván Peñas, Miren Itxaso Calafel, Roberto Hernández Aguirresarobe, Manuel Tierno, José Ignacio Conde, Belén Pascual and Antxon Santamaría
Polymers 2020, 12(9), 2070; https://doi.org/10.3390/polym12092070 - 12 Sep 2020
Cited by 12 | Viewed by 2908
Abstract
New auto-plasticised copolymers of poly(vinyl chloride)-r-(acrylate) and polyvinylchloride, obtained by radical polymerization, are investigated to analyse their capacity to be processed by 3D printing. The specific microstructure of the copolymers gives rise to a phase-separated morphology constituted by poly(vinyl chloride) (PVC) domains dispersed [...] Read more.
New auto-plasticised copolymers of poly(vinyl chloride)-r-(acrylate) and polyvinylchloride, obtained by radical polymerization, are investigated to analyse their capacity to be processed by 3D printing. The specific microstructure of the copolymers gives rise to a phase-separated morphology constituted by poly(vinyl chloride) (PVC) domains dispersed in a continuous phase of acrylate-vinyl chloride copolymer. The analysis of the rheological results allows the suitability of these copolymers to be assessed for use in a screw-driven 3D printer, but not by the fused filament fabrication method. This is due to the high melt elasticity of the copolymers, caused by interfacial tension between phases. A relationship between the relaxation modulus of the copolymers and the interlayer adhesion is established. Under adequate 3D-printing conditions, flexible and ductile samples with good dimensional stability and cohesion are obtained, as is proven by scanning electron microscopy (SEM) and tensile stress-strain tests. Full article
(This article belongs to the Special Issue Rheology of 3D Printing)
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15 pages, 7650 KiB  
Article
Effects of Scanning Strategy and Printing Temperature on the Compressive Behaviors of 3D Printed Polyamide-Based Composites
by Jin Wang, Jiangyang Xiang, Hao Lin, Kui Wang, Song Yao, Yong Peng and Yanni Rao
Polymers 2020, 12(8), 1783; https://doi.org/10.3390/polym12081783 - 10 Aug 2020
Cited by 22 | Viewed by 3125
Abstract
In this work, the effects of scanning strategies and printing temperature on mechanical properties and crush behaviors of columns manufactured using the fused deposition modeling (FDM) technique were studied. The results showed that scanning strategy and printing temperature had significant influences on mechanical [...] Read more.
In this work, the effects of scanning strategies and printing temperature on mechanical properties and crush behaviors of columns manufactured using the fused deposition modeling (FDM) technique were studied. The results showed that scanning strategy and printing temperature had significant influences on mechanical response and deformation mode of the columns. The columns printed in different scanning strategies showed significant anisotropy due to the preferred orientation of short fibers during the printing process. The columns printed in a circular direction presented the highest compressive force response. The columns printed with carbon fiber-reinforced polyamide in a circular direction showed the final oblique fracture failure mode, in which there were fiber pull-out and matrix pull-apart on fracture surfaces. Different indicators were also used to evaluate the mechanical properties and crushing characteristics of the columns. The carbon fiber reinforcement columns presented the highest energy absorption, and the glass fiber reinforcement columns showed the highest elastic modulus and yield strength. The results indicated that the scanning strategy and printing temperature not only influenced the elastic modulus and yield strength, but also affected the energy absorption performances of the columns. Full article
(This article belongs to the Special Issue Rheology of 3D Printing)
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Review

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27 pages, 7415 KiB  
Review
Self-Healing Mechanisms for 3D-Printed Polymeric Structures: From Lab to Reality
by Mohammed Dukhi Almutairi, Adrianus Indrat Aria, Vijay Kumar Thakur and Muhammad A. Khan
Polymers 2020, 12(7), 1534; https://doi.org/10.3390/polym12071534 - 11 Jul 2020
Cited by 35 | Viewed by 8484
Abstract
Existing self-healing mechanisms are still very far from full-scale implementation, and most published work has only demonstrated damage cure at the laboratory level. Their rheological nature makes the mechanisms for damage cure difficult to implement, as the component or structure is expected to [...] Read more.
Existing self-healing mechanisms are still very far from full-scale implementation, and most published work has only demonstrated damage cure at the laboratory level. Their rheological nature makes the mechanisms for damage cure difficult to implement, as the component or structure is expected to continue performing its function. In most cases, a molecular bond level chemical reaction is required for complete healing with external stimulations such as heating, light and temperature change. Such requirements of external stimulations and reactions make the existing self-healing mechanism almost impossible to implement in 3D printed products, particularly in critical applications. In this paper, a conceptual description of the self-healing phenomenon in polymeric structures is provided. This is followed by how the concept of self-healing is motivated by the observation of nature. Next, the requirements of self-healing in modern polymeric structures and components are described. The existing self-healing mechanisms for 3D printed polymeric structures are also detailed, with a special emphasis on their working principles and advantages of the self-healing mechanism. A critical discussion on the challenges and limitations in the existing working principles is provided at the end. A novel self-healing idea is also proposed. Its ability to address current challenges is assessed in the conclusions. Full article
(This article belongs to the Special Issue Rheology of 3D Printing)
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