Advance in 3D/4D Printing of Polymeric Materials

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

Deadline for manuscript submissions: closed (25 May 2024) | Viewed by 17116

Special Issue Editors


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Guest Editor
Lawrence Livermore National Laboratory, Livermore, CA, USA
Interests: additive manufacturing; 3D printing; 4D printing; polymer chemistry; responsive materials

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Guest Editor
Department of Engineering Science, Faculty of Engineering, Babeș-Bolyai University, 32008 Reșița, Romania
Interests: mechanical properties of materials; mechanics of materials; finite element analysis; stress; strain; additive manufacturing
Special Issues, Collections and Topics in MDPI journals
Department of Chemistry, University of North Carolina Chapel Hill, Chapel Hill, NC 27599, USA
Interests: polymer physics; polymer reactions; polymer composite; graphene; computation; molecular simulation; 2D material; soft material
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) as a field of research has seen significant advancement in areas including systems engineering, software, modelling, materials chemistry, and quality certification. In terms of polymer-based AM methods specifically, the materials toolset is constantly expanding to include the printing of materials for engineering, biocompatible, and responsive formulations. These materials coupled with the geometric freedom of 3D printing enable research towards applications in personalized medicine, microfluidics, load-bearing structures, soft robotics, aerospace, and automotive industries. Furthermore, incorporating responsive materials, such as shape memory materials, can produce structures with programmable restructuring. Stimulus-induced structural change is termed 4D printing, and provides yet another facet of control for design freedom. 

This Special Issue will focus specifically on advancements that expand the capabilities of 3D and 4D printing in relation to polymeric materials. The highlighted focus will be on novel materials and chemical understanding, including composite, responsive, biocompatible, and engineering formulations.

Dr. Johanna J. Schwartz
Dr. Vasile Cojocaru
Dr. Zilu Wang
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • additive manufacturing
  • 3D printing
  • 4D printing
  • polymer chemistry
  • responsive materials

Published Papers (14 papers)

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Research

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15 pages, 6511 KiB  
Article
Influence of Manufacturing Process on the Conductivity of Material Extrusion Components: A Comparison between Filament- and Granule-Based Processes
by Maximilian Nowka, Karl Hilbig, Lukas Schulze, Timo Heller, Marijn Goutier and Thomas Vietor
Polymers 2024, 16(8), 1134; https://doi.org/10.3390/polym16081134 - 18 Apr 2024
Viewed by 586
Abstract
The additive manufacturing of components using material extrusion (MEX) enables the integration of several materials into one component, including functional structures such as electrically conductive structures. This study investigated the influence of the selected additive MEX process on the resistivity of MEX structures. [...] Read more.
The additive manufacturing of components using material extrusion (MEX) enables the integration of several materials into one component, including functional structures such as electrically conductive structures. This study investigated the influence of the selected additive MEX process on the resistivity of MEX structures. Specimens were produced from filaments and granules of an electrically conductive PLA and filled with carbon nanotubes and carbon black. Specimens were produced with a full-factorial variation of the input variables: extrusion temperature, deposition speed, and production process. The resistivity of the specimens was determined by four-wire measurement. Analysis of the obtained data showed that only the extrusion temperature had a significant influence on the resistivity of the MEX specimens. Furthermore, the impact of the nozzle diameter was evaluated by comparing the results of this study with those of a previous study, with an otherwise equal experimental setup. The nozzle diameter had a significant influence on resistivity and a larger nozzle diameter reduced the mean variance by an order of magnitude. The resistivity was lower for most process parameter sets. As the manufacturing process had no significant influence on the resistivity of MEX structures, it can be selected based on other criteria, e.g., the cost of feedstock. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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13 pages, 6470 KiB  
Article
Tailoring the Mass Density of 3D Printing Materials for Accurate X-ray Imaging Simulation by Controlled Underfilling for Radiographic Phantoms
by Ahmed Mahmoud Mabrouk Ahmed, Martin Buschmann, Lara Breyer, Claudia Kuntner and Peter Homolka
Polymers 2024, 16(8), 1116; https://doi.org/10.3390/polym16081116 - 16 Apr 2024
Viewed by 918
Abstract
Additive manufacturing and 3D printing allow for the design and rapid production of radiographic phantoms for X-ray imaging, including CT. These are used for numerous purposes, such as patient simulation, optimization of imaging procedures and dose levels, system evaluation and quality assurance. However, [...] Read more.
Additive manufacturing and 3D printing allow for the design and rapid production of radiographic phantoms for X-ray imaging, including CT. These are used for numerous purposes, such as patient simulation, optimization of imaging procedures and dose levels, system evaluation and quality assurance. However, standard 3D printing polymers do not mimic X-ray attenuation properties of tissues like soft, adipose, lung or bone tissue, and standard materials like liquid water. The mass density of printing polymers—especially important in CT—is often inappropriate, i.e., mostly too high. Different methods can be applied to reduce mass density. This work examines reducing density by controlled underfilling either realized by using 3D printing materials expanded through foaming during heating in the printing process, or reducing polymer flow to introduce microscopic air-filled voids. The achievable density reduction depends on the base polymer used. When using foaming materials, density is controlled by the extrusion temperature, and ranges from 33 to 47% of the base polymer used, corresponding to a range of −650 to −394 HU in CT with 120 kV. Standard filaments (Nylon, modified PLA and modified ABS) allowed density reductions by 20 to 25%, covering HU values in CT from −260 to 77 (Nylon), −230 to −20 (ABS) and −81 to 143 (PLA). A standard chalk-filled PLA filament allowed reproduction of bone tissue in a wide range of bone mineral content resulting in CT numbers from 57 to 460 HU. Controlled underfilling allowed the production of radiographic phantom materials with continuously adjustable attenuation in a limited but appropriate range, allowing for the reproduction of X-ray attenuation properties of water, adipose, soft, lung, and bone tissue in an accurate, predictable and reproducible manner. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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14 pages, 3014 KiB  
Article
Effect of Aging on Tensile and Chemical Properties of Polylactic Acid and Polylactic Acid-Like Polymer Materials for Additive Manufacturing
by Zorana Golubović, Božica Bojović, Snežana Kirin, Aleksa Milovanović, Ljubiša Petrov, Boban Anđelković and Ivana Sofrenić
Polymers 2024, 16(8), 1035; https://doi.org/10.3390/polym16081035 - 10 Apr 2024
Viewed by 536
Abstract
Additive manufacturing, with its fast development and application of polymeric materials, led to the wide utilization of polylactic acid (PLA) materials. As a biodegradable and biocompatible aliphatic polyester, produced from renewable sources, PLA is widely used in different sectors, from industry to medicine [...] Read more.
Additive manufacturing, with its fast development and application of polymeric materials, led to the wide utilization of polylactic acid (PLA) materials. As a biodegradable and biocompatible aliphatic polyester, produced from renewable sources, PLA is widely used in different sectors, from industry to medicine and science. The aim of this research is to determine the differences between two forms of the PLA material, i.e., fused deposition modeling (FDM) printed filament and digital light processing (DLP) printed resin, followed by aging due to environmental and hygiene maintenance conditions for a period of two months. Specimens underwent 3D scanning, tensile testing, and Fourier transform infrared (FTIR) spectrometry to obtain insights into the material changes that occurred. Two-way Analysis of Variance (ANOVA) statistical analysis was subsequently carried out to determine the statistical significance of the determined changes. Significant impairment can be observed in the dimensional accuracies between both materials, whether they are non-aged or aged. The mechanical properties fluctuated for aged FDM specimens: 15% for ultimate tensile stress, 15% for elongation at yield, and 12% for elastic modulus. Regarding the DLP aged specimens, the UTS decreased by 61%, elongation at yield by around 61%, and elastic modulus by 62%. According to the FTIR spectral analysis, the PLA materials degraded, especially in the case of resin specimens. Aging also showed a significant influence on the elastic modulus, ultimate tensile stress, elongation at yield, elongation at break, and toughness of both materials, which was statistically shown by means of a two-way ANOVA test. The data collected in this research give a better understanding of the underlying aging mechanism of PLA materials. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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22 pages, 6469 KiB  
Article
Aortic Valve Engineering Advancements: Precision Tuning with Laser Sintering Additive Manufacturing of TPU/TPE Submillimeter Membranes
by Vlad Ciobotaru, Marcos Batistella, Emily De Oliveira Emmer, Louis Clari, Arthur Masson, Benoit Decante, Emmanuel Le Bret, José-Marie Lopez-Cuesta and Sebastien Hascoet
Polymers 2024, 16(7), 900; https://doi.org/10.3390/polym16070900 - 25 Mar 2024
Viewed by 727
Abstract
Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to [...] Read more.
Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to their notable stability, fatigue resistance, and customizable properties such as shear strength and elasticity. This study explores the additive manufacturing technique of selective laser sintering (SLS) for TPUs and TPEs to optimize process parameters to balance flexibility and strength, mimicking aortic valve tissue properties. Additionally, it aims to assess the feasibility of printing aortic valve models with submillimeter membranes. The results demonstrate that the SLS-TPU/TPE technique can produce micrometric valve structures with soft shape memory properties, resembling aortic tissue in strength, flexibility, and fineness. These models show promise for surgical training and manipulation, display intriguing echogenicity properties, and can potentially be personalized to shape biocompatible valve substitutes. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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16 pages, 6231 KiB  
Article
Lap Shear Strength and Fatigue Analysis of Continuous Carbon-Fibre-Reinforced 3D-Printed Thermoplastic Composites by Varying the Load and Fibre Content
by Khalid Saeed, Alistair Mcilhagger, Thomas Dooher, Jawad Ullah, Faisal Manzoor, Xavier Velay and Edward Archer
Polymers 2024, 16(5), 579; https://doi.org/10.3390/polym16050579 - 21 Feb 2024
Viewed by 783
Abstract
This study focuses on evaluating the fatigue life performance of 3D-printed polymer composites produced through the fused deposition modelling (FDM) technique. Fatigue life assessment is essential in designing components for industries like aerospace, medical, and automotive, as it provides an estimate of the [...] Read more.
This study focuses on evaluating the fatigue life performance of 3D-printed polymer composites produced through the fused deposition modelling (FDM) technique. Fatigue life assessment is essential in designing components for industries like aerospace, medical, and automotive, as it provides an estimate of the component’s safe service life during operation. While there is a lack of detailed research on the fatigue behaviour of 3D-printed polymer composites, this paper aims to fill that gap. Fatigue tests were conducted on the 3D-printed polymer composites under various loading conditions, and static (tensile) tests were performed to determine their ultimate tensile strength. The fatigue testing load ranged from 80% to 98% of the total static load. The results showed that the fatigue life of the pressed samples using a platen press was significantly better than that of the non-pressed samples. Samples subjected to fatigue testing at 80% of the ultimate tensile strength (UTS) did not experience failure even after 1 million cycles, while samples tested at 90% of UTS failed after 50,000 cycles, with the failure being characterized as splitting and clamp area failure. This study also included a lap shear analysis of the 3D-printed samples, comparing those that were bonded using a two-part Araldite glue to those that were fabricated as a single piece using the Markforged Mark Two 3D printer. In summary, this study sheds light on the fatigue life performance of 3D-printed polymer composites fabricated using the FDM technique. The results suggest that the use of post-printing platen press improved the fatigue life of 3D-printed samples, and that single printed samples have better strength of about 265 MPa than adhesively bonded samples in which the strength was 56 MPa. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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18 pages, 16317 KiB  
Article
Rheological and Mechanical Characterization of 3D-Printable Solid Propellant Slurry
by Alessandra Zumbo, Leonardo Stumpo, Paola Antonaci, Andrea Ferrero, Filippo Masseni, Giovanni Polizzi, Giacomo Tetti and Dario Pastrone
Polymers 2024, 16(5), 576; https://doi.org/10.3390/polym16050576 - 20 Feb 2024
Viewed by 796
Abstract
This study delves into the rheological and mechanical properties of a 3D-printable composite solid propellant with 80% wt solids loading. Polybutadiene is used as a binder with ammonium sulfate, which is added as an inert replacement for the ammonium perchlorate oxidizer. Further additives [...] Read more.
This study delves into the rheological and mechanical properties of a 3D-printable composite solid propellant with 80% wt solids loading. Polybutadiene is used as a binder with ammonium sulfate, which is added as an inert replacement for the ammonium perchlorate oxidizer. Further additives are introduced to allow for UV curing. An in-house illumination system made of four UV-A LEDs (385 nm) is employed to cure the resulting slurry. Rheological and mechanical tests are conducted to evaluate the viscosity, ultimate tensile strength and strain, and compression behavior. Viscosity tests are performed for both pure resin and complete propellant composition. A viscosity reduction factor is obtained for the tested formulations when pre-heating slurry. Uniaxial tensile and compression tests reveal that the mechanical properties are consistent with previous research. Results emphasize the critical role of temperature and solid loading percentage. Pre-heating resin composites may grant a proper viscosity reduction while keeping mechanical properties in the applicability range. Overall, these findings pave the way for the development of a 3D printer prototype for composite solid propellants. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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30 pages, 11610 KiB  
Article
An Insight into the Characteristics of 3D Printed Polymer Materials for Orthoses Applications: Experimental Study
by Syed Hammad Mian, Emad Abouel Nasr, Khaja Moiduddin, Mustafa Saleh and Hisham Alkhalefah
Polymers 2024, 16(3), 403; https://doi.org/10.3390/polym16030403 - 31 Jan 2024
Viewed by 798
Abstract
Knee orthoses assist patients with impaired gait through the amendment of knee abnormalities, restoration of mobility, alleviation of pain, shielding, and immobilization. The inevitable issues with laborious traditional plaster molding procedures for orthoses can be resolved with 3D printing. However, a number of [...] Read more.
Knee orthoses assist patients with impaired gait through the amendment of knee abnormalities, restoration of mobility, alleviation of pain, shielding, and immobilization. The inevitable issues with laborious traditional plaster molding procedures for orthoses can be resolved with 3D printing. However, a number of challenges have limited the adoption of 3D printing, the most significant of which is the proper material selection for orthoses. This is so because the material used to make an orthosis affects its strength, adaptability, longevity, weight, moisture response, etc. This study intends to examine the mechanical, physical, and dimensional characteristics of three-dimensional (3D) printing materials (PLA, ABS, PETG, TPU, and PP). The aim of this investigation is to gain knowledge about these materials’ potential for usage as knee orthosis materials. Tensile testing, Olympus microscope imaging, water absorption studies, and coordinate measuring machine-based dimension analysis are used to characterize the various 3D printing materials. Based on the investigation, PLA outperforms all other materials in terms of yield strength (25.98 MPa), tensile strength (30.89 MPa), and shrinkage (0.46%). PP is the least water absorbent (0.15%) and most flexible (407.99%); however, it is the most difficult to fabricate using 3D printing. When producing knee orthoses with 3D printing, PLA can be used for the orthosis frame and other structural elements, PLA or ABS for moving parts like hinges, PP for padding, and TPU or PP for the straps. This study provides useful information for scientists and medical professionals who are intrigued about various polymer materials for 3D printing and their effective utilization to fabricate knee orthoses. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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15 pages, 3622 KiB  
Article
3D Printing of Flexible Mechanical Metamaterials: Synergistic Design of Process and Geometric Parameters
by Nan Li, Chenhao Xue, Shenggui Chen, Wurikaixi Aiyiti, Sadaf Bashir Khan, Jiahua Liang, Jianping Zhou and Bingheng Lu
Polymers 2023, 15(23), 4523; https://doi.org/10.3390/polym15234523 - 24 Nov 2023
Cited by 3 | Viewed by 1489
Abstract
Mechanical metamaterials with ultralight and ultrastrong mechanical properties are extensively employed in various industrial sectors, with three-periodic minimal surface (TPMS) structures gaining significant research attention due to their symmetry, equation-driven characteristics, and exceptional mechanical properties. Compared to traditional lattice structures, TPMS structures exhibit [...] Read more.
Mechanical metamaterials with ultralight and ultrastrong mechanical properties are extensively employed in various industrial sectors, with three-periodic minimal surface (TPMS) structures gaining significant research attention due to their symmetry, equation-driven characteristics, and exceptional mechanical properties. Compared to traditional lattice structures, TPMS structures exhibit superior mechanical performance. The mechanical properties of TPMS structures depend on the base material, structural porosity (volume fraction), and wall thickness. Hard rigid lattice structures such as Gyroid, diamond, and primitive exhibit outstanding performance in terms of elastic modulus, energy absorption, heat dissipation, and heat transfer. Flexible TPMS lattice structures, on the other hand, offer higher elasticity and recoverable large deformations, drawing attention for use in applications such as seat cushions and helmet impact-absorbing layers. Conventional fabrication methods often fail to guarantee the quality of TPMS structure samples, and additive manufacturing technology provides a new avenue. Selective laser sintering (SLS) has successfully been used to process various materials. However, due to the layer-by-layer manufacturing process, it cannot eliminate the anisotropy caused by interlayer bonding, which impacts the mechanical properties of 3D-printed parts. This paper introduces a process data-driven optimization design approach for TPMS structure geometry by adjusting volume fraction gradients to overcome the elastic anisotropy of 3D-printed isotropic lattice structures. Experimental validation and analysis are conducted using TPMS structures fabricated using TPU material via SLS. Furthermore, the advantages of volume fraction gradient-designed TPMS structures in functions such as energy absorption and heat dissipation are explored. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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10 pages, 2348 KiB  
Article
Progress on a Novel, 3D-Printable Heart Valve Prosthesis
by Filip Schröter, Ralf-Uwe Kühnel, Martin Hartrumpf, Roya Ostovar and Johannes Maximilian Albes
Polymers 2023, 15(22), 4413; https://doi.org/10.3390/polym15224413 - 15 Nov 2023
Cited by 1 | Viewed by 1214
Abstract
(1) Background: Polymeric heart valves are prostheses constructed out of flexible, synthetic materials to combine the advantageous hemodynamics of biological valves with the longevity of mechanical valves. This idea from the early days of heart valve prosthetics has experienced a renaissance in recent [...] Read more.
(1) Background: Polymeric heart valves are prostheses constructed out of flexible, synthetic materials to combine the advantageous hemodynamics of biological valves with the longevity of mechanical valves. This idea from the early days of heart valve prosthetics has experienced a renaissance in recent years due to advances in polymer science. Here, we present progress on a novel, 3D-printable aortic valve prosthesis, the TIPI valve, removing the foldable metal leaflet restrictor structure in its center. Our aim is to create a competitive alternative to current valve prostheses made from flexible polymers. (2) Methods: Three-dimensional (3D) prototypes were designed and subsequently printed in silicone. Hemodynamic performance was measured with an HKP 2.0 hemodynamic testing device using an aortic valve bioprosthesis (BP), a mechanical prosthesis (MP), and the previously published prototype (TIPI 2.2) as benchmarks. (3) Results: The latest prototype (TIPI 3.4) showed improved performance in terms of regurgitation fraction (TIPI 3.4: 15.2 ± 3.7%, TIPI 2.2: 36.6 ± 5.0%, BP: 8.8 ± 0.3%, MP: 13.2 ± 0.7%), systolic pressure gradient (TIPI 3.4: 11.0 ± 2.7 mmHg, TIPI 2.2: 12.8 ± 2.2 mmHg, BP: 8.2 ± 0.9 mmHg, MP: 10.5 ± 0.6 mmHg), and effective orifice area (EOA, TIPI 3.4: 1.39 cm2, TIPI 2.2: 1.28 cm2, BP: 1.58 cm2, MP: 1.38 cm2), which was equivalent to currently used aortic valve prostheses. (4) Conclusions: Removal of the central restrictor structure alleviated previous concerns about its potential thrombogenicity and significantly increased the area of unobstructed opening. The prototypes showed unidirectional leaflet movement and very promising performance characteristics within our testing setup. The resulting simplicity of the shape compared to other approaches for polymeric heart valves could be suitable not only for 3D printing, but also for fast and easy mass production using molds and modern, highly biocompatible polymers. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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17 pages, 7320 KiB  
Article
A Comprehensive Mechanical Examination of ABS and ABS-like Polymers Additively Manufactured by Material Extrusion and Vat Photopolymerization Processes
by Zorana Golubović, Ivan Danilov, Božica Bojović, Ljubiša Petrov, Aleksandar Sedmak, Žarko Mišković and Nenad Mitrović
Polymers 2023, 15(21), 4197; https://doi.org/10.3390/polym15214197 - 24 Oct 2023
Cited by 2 | Viewed by 1366
Abstract
Additive manufacturing technologies have developed rapidly in recent decades, pushing the limits of known manufacturing processes. The need to study the properties of the different materials used for these processes comprehensively and in detail has become a primary goal in order to get [...] Read more.
Additive manufacturing technologies have developed rapidly in recent decades, pushing the limits of known manufacturing processes. The need to study the properties of the different materials used for these processes comprehensively and in detail has become a primary goal in order to get the best out of the manufacturing itself. The widely used thermoplastic polymer material acrylonitrile butadiene styrene (ABS) was selected in the form of both filaments and ABS-like resins to investigate and compare the mechanical properties through a series of different tests. ABS-like resin material is commercially available, but it is not a sufficiently mechanically studied form of the material, which leads to the rather limited literature. Considering that ABS resin is a declared material that behaves like the ABS filament but in a different form, the objective of this study was to compare these two commercially available materials printed with three different 3D printers, namely Fused Deposition Modelling (FDM), Stereolithography (SLA) and Digital Light Processing (DLP). A total of 45 test specimens with geometries and test protocols conforming to the relevant standards were subjected to a series of tensile, three-point bending and compression tests to determine their mechanical properties. Characterization also included evaluation of morphology with 2D and 3D microscopy, dimensional accuracy of 3D scans, and Shore A hardness of each material and 3D printing process. Tensile testing results have shown that FDM toughness is 40% of the value for DLP. FDM elongation at break is 37% of DLP, while ultimate tensile stress for SLA is 27% higher than FDM value. Elastic modulus for FDM and SLA coincide. Flexure testing results indicate that value of DLP flexural modulus is 54% of the FDM value. SLA strain value is 59% of FDM, and DLP ultimate flexure stress is 77% of the value for FDM. Compression test results imply that FDM specimens absorb at least twice as much energy as vat polymerized specimens. Strain at break for SLA is 72% and strain at ultimate stress is 60% of FDM values. FDM yield stress is 32% higher than DLP value. SLA ultimate compressive stress is half of FDM, while value for DLP compressive modulus is 69% of the FDM value. The results obtained are beneficial and give a more comprehensive picture of the behavior of the ABS polymers used in different forms and different AM processes. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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14 pages, 2563 KiB  
Article
Optimisation of 3D Printing for Microcellular Polymers
by Christian Andrew Griffiths, Andrew Rees, Adam Morgan and Feras Korkees
Polymers 2023, 15(19), 3910; https://doi.org/10.3390/polym15193910 - 27 Sep 2023
Cited by 2 | Viewed by 1092
Abstract
Polymers are extensively used in various industries due to their versatility, durability and cost-effectiveness. To ensure functionality and longevity, polymer parts must have sufficient strength to endure external forces without deformation or breakage. Traditional approaches to increasing part strength involve adding more material; [...] Read more.
Polymers are extensively used in various industries due to their versatility, durability and cost-effectiveness. To ensure functionality and longevity, polymer parts must have sufficient strength to endure external forces without deformation or breakage. Traditional approaches to increasing part strength involve adding more material; however, balancing strength to weight relationships is challenging. This paper explorers the viability of manufacturing lightweight components using a microcellular foaming polymer. Microcellular foaming has emerged as a helpful tool to achieve an optimal strength-to-weight ratio; offering advantages such as lightweight, improved mechanical properties, reduced material usage, better insulation and improved cost-effectiveness. It can also contribute to improved fuel efficiency and reduced carbon emissions, making them environmentally favourable. The combination of additive manufacturing (AM) and microcellular foaming has opened new possibilities for design innovation. This text highlights the challenges and efforts in incorporating foaming techniques into 3D printing processes, specifically fused filament fabrication (FFF). This study reveals that microcellular polymers are a viable option when balancing part strength and weight. The experiments completed during the formulation of this paper demonstrated that lightweight LW-PLA parts were significantly lighter than standard PLA parts and that a design of experiments approach can be used to optimise strength properties and provide insights into optimising manufacturability. Microcellular polymers present an opportunity for lighter and stronger 3D printed parts, offering potential energy and material savings for sustainable manufacturing practices. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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17 pages, 3199 KiB  
Article
Modulation of the Lower Critical Solution Temperature of Thermoresponsive Poly(N-vinylcaprolactam) Utilizing Hydrophilic and Hydrophobic Monomers
by Elaine Halligan, Shuo Zhuo, Declan Mary Colbert, Mohamad Alsaadi, Billy Shu Hieng Tie, Gilberto S. N. Bezerra, Gavin Keane and Luke M. Geever
Polymers 2023, 15(7), 1595; https://doi.org/10.3390/polym15071595 - 23 Mar 2023
Cited by 2 | Viewed by 1606
Abstract
Four-dimensional printing is primarily based on the concept of 3D printing technology. However, it requires additional stimulus and stimulus-responsive materials. Poly-N-vinylcaprolactam is a temperature-sensitive polymer. Unique characteristics of poly-N-vinylcaprolactam -based hydrogels offer the possibility of employing them in 4D [...] Read more.
Four-dimensional printing is primarily based on the concept of 3D printing technology. However, it requires additional stimulus and stimulus-responsive materials. Poly-N-vinylcaprolactam is a temperature-sensitive polymer. Unique characteristics of poly-N-vinylcaprolactam -based hydrogels offer the possibility of employing them in 4D printing. The main aim of this study is to alter the phase transition temperature of poly-N-vinylcaprolactam hydrogels. This research focuses primarily on incorporating two additional monomers with poly-N-vinylcaprolactam: Vinylacetate and N-vinylpyrrolidone. This work contributes to this growing area of research by altering (increasing and decreasing) the lower critical solution temperature of N-vinylcaprolactam through photopolymerisation. Poly-N-vinylcaprolactam exhibits a lower critical solution temperature close to the physiological temperature range of 34–37 °C. The copolymers were analysed using various characterisation techniques, such as FTIR, DSC, and UV-spectrometry. The main findings show that the inclusion of N-vinylpyrrolidone into poly-N-vinylcaprolactam increased the lower critical solution temperature above the physiological temperature. By incorporating vinylacetate, the lower critical solution temperature dropped to 21 °C, allowing for potential self-assembly of 4D-printed objects at room temperature. In this case, altering the lower critical solution temperature of the material can potentially permit the transformation of the 4D-printed object at a particular temperature. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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Review

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33 pages, 8608 KiB  
Review
Cellulose-Reinforced Polylactic Acid Composites for Three-Dimensional Printing Using Polyethylene Glycol as an Additive: A Comprehensive Review
by Kelly Cristina Coelho de Carvalho Benini, Anne Shayene Campos de Bomfim and Herman Jacobus Cornelis Voorwald
Polymers 2023, 15(19), 3960; https://doi.org/10.3390/polym15193960 - 30 Sep 2023
Cited by 2 | Viewed by 1552
Abstract
Growing concerns about environmental issues and global warming have garnered increased attention in recent decades. Consequently, the use of materials sourced from renewable and biodegradable origins, produced sustainably, has piqued the interest of scientific researchers. Biodegradable and naturally derived polymers, such as cellulose [...] Read more.
Growing concerns about environmental issues and global warming have garnered increased attention in recent decades. Consequently, the use of materials sourced from renewable and biodegradable origins, produced sustainably, has piqued the interest of scientific researchers. Biodegradable and naturally derived polymers, such as cellulose and polylactic acid (PLA), have consistently been the focus of scientific investigation. The objective is to develop novel materials that could potentially replace conventional petroleum-based polymers, offering specific properties tailored for diverse applications while upholding principles of sustainability and technology as well as economic viability. Against this backdrop, the aim of this review is to provide a comprehensive overview of recent advancements in research concerning the use of polylactic acid (PLA) and the incorporation of cellulose as a reinforcing agent within this polymeric matrix, alongside the application of 3D printing technology. Additionally, a pivotal additive in the combination of PLA and cellulose, polyethylene glycol (PEG), is explored. A systematic review of the existing literature related to the combination of these materials (PLA, cellulose, and PEG) and 3D printing was conducted using the Web of Science and Scopus databases. The outcomes of this search are presented through a comparative analysis of diverse studies, encompassing aspects such as the scale and cellulose amount added into the PLA matrix, modifications applied to cellulose surfaces, the incorporation of additives or compatibilizing agents, variations in molecular weight and in the quantity of PEG introduced into the PLA/cellulose (nano)composites, and the resulting impact of these variables on the properties of these materials. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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19 pages, 3178 KiB  
Review
Innovative Polymer Composites with Natural Fillers Produced by Additive Manufacturing (3D Printing)—A Literature Review
by Beata Anwajler, Ewa Zdybel and Ewa Tomaszewska-Ciosk
Polymers 2023, 15(17), 3534; https://doi.org/10.3390/polym15173534 - 24 Aug 2023
Cited by 6 | Viewed by 2169
Abstract
In recent years, plastics recycling has become one of the leading environmental and waste management issues. Along with the main advantage of plastics, which is undoubtedly their long life, the problem of managing their waste has arisen. Recycling is recognised as the preferred [...] Read more.
In recent years, plastics recycling has become one of the leading environmental and waste management issues. Along with the main advantage of plastics, which is undoubtedly their long life, the problem of managing their waste has arisen. Recycling is recognised as the preferred option for waste management, with the aim of reusing them to create new products using 3D printing. Additive manufacturing (AM) is an emerging and evolving rapid tooling technology. With 3D printing, it is possible to achieve lightweight structures with high dimensional accuracy and reduce manufacturing costs for non-standard geometries. Currently, 3D printing research is moving towards the production of materials not only of pure polymers but also their composites. Bioplastics, especially those that are biodegradable and compostable, have emerged as an alternative for human development. This article provides a brief overview of the possibilities of using thermoplastic waste materials through the application of 3D printing, creating innovative materials from recycled and naturally derived materials, i.e., biomass (natural reinforcing fibres) in 3D printing. The materials produced from them are ecological, widely available and cost-effective. Research activities related to the production of bio-based materials have gradually increased over the last two decades, with the aim of reducing environmental problems. This article summarises the efforts made by researchers to discover new innovative materials for 3D printing. Full article
(This article belongs to the Special Issue Advance in 3D/4D Printing of Polymeric Materials)
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