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Polymers and Their Application in 3D Printing

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

Deadline for manuscript submissions: closed (15 November 2022) | Viewed by 39268

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Special Issue Editors

Dr. Hamid Reza Vanaei

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Guest Editor

Laboratoire d'Ingénierie des Fluides et des Systèmes Énergétiques (LIFSE), Arts et Métiers Institute of Technology, Paris, France
Interests: additive manufacturing; 3D printing of polymers; 3D bioprinting; rheology of materials; mechanics of materials
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Sofiane Khelladi

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Guest Editor

Arts et Métiers Institute of Technology, CNAM, LIFSE, HESAM University, 75013 Paris, France
Interests: CFD; computational aeroacoustics; complex fluid flows
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Abbas Tcharkhtchi

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Guest Editor

Arts et Métiers Institute of Technology, CNRS, CNAM, PIMM, HESAM University, 75013 Paris, France
Interests: polymers and composites; polymer processing; mechanical properties; solid mechanics; fracture mechanics; material characterization; additive manufacturing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fused filament fabrication, also known as 3D printing, is extensively used to produce prototypes for applications in, e.g., the aerospace, medical, and automotive industries. In this process, a thermoplastic polymer is fed into a liquefier that extrudes a filament while moving in successive X–Y planes along the Z direction to fabricate a 3D part in a layer-by-layer process. Due to the progressive advances of this process in industry, the application of polymeric (or even composite) materials have received much attention. Researchers and industries now engage in 3D printing by implementing numerous polymeric materials in their domain. In this Special Issue, we will present a collection of recent and novel works regarding the application of polymers in 3D printing.

Dr. Hamid Reza Vanaei
Prof. Dr. Sofiane Khelladi
Prof. Dr. Abbas Tcharkhtchi
Guest Editors

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

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

3D printing
polymer characterization
turbomachinery
rheology
3D printed rotor

Published Papers (14 papers)

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Research

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11 pages, 3124 KiB

Open AccessArticle

Fabrication and Thermal Performance of a Polymer-Based Flexible Oscillating Heat Pipe via 3D Printing Technology

by Zhaoyang Han and Chao Chang

Polymers 2023, 15(2), 414; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15020414 - 12 Jan 2023

Cited by 7 | Viewed by 2346

Abstract

As flexible electronic technologies rapidly developed with a requirement for multifunction, miniaturization, and high power density, effective thermal management has become an increasingly important issue. The oscillating heat pipe, as a promising technology, was used to dissipate high heat fluxes and had a wide range of applications. In this paper, we reported the fabrication and heat transfer performance evaluation of a polymer-based flexible oscillating heat pipe (FOHP) prepared using 3D printing technology. The 3D-printed inner surface presented excellent wettability to the working fluid, which was beneficial for the evaporation of the working fluid. Ethanol was selected as the working fluid, and the influence of the filling ratios range of 30–60% on heat transfer performance was analyzed. It was found that a 3D-printed FOHP with a filling ratio of 40% presented the best heat transfer performance with the lowest thermal resistance, and the fabricated heat pipes could be easily bent from 0° to 90°. With the best filling ratio, the thermal resistance of the FOHPs increased with larger bending angles. In addition, the 3D-printed FOHP was successfully applied for the thermal management of flexible printed circuits, and the results showed that the temperature of flexible printed circuits was kept within 72 °C, and its service life was guaranteed. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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15 pages, 3496 KiB

Open AccessArticle

Predicting the Bending of 3D Printed Hyperelastic Polymer Components

by Lucas Gallup, Mohamed Trabia, Brendan O’Toole and Youssef Fahmy

Polymers 2023, 15(2), 368; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15020368 - 10 Jan 2023

Viewed by 1468

Abstract

The advancement of 3D printing has led to its widespread use. NinjaFlex^®, a thermoplastic polyurethane (TPU) filament, is a highly durable and flexible material that has been used to create flexible parts. While this material has been available for nearly two decades, the mechanical properties of 3D printed NinjaFlex^® parts are not well-understood, especially in bending. The focus of this research was predicting the behavior of small 3D printed NinjaFlex^® components. Three-dimensionally printed rectangular specimens of varying lengths and aspect ratios were loaded as cantilevers. The deflection of these specimens was measured using a computer. The experimental results were compared to a modified form of the Euler–Bernoulli Beam Theorem (MEB), which was developed to account for nonlinearities associated with large deflection. Additionally, experimental results were compared to the finite element analysis (FEA). The results showed that both modeling approaches were overall accurate, with the average difference between experimental deflection data and MEB predictions ranging from 0.6% to 3.0%, while the FEA predictions ranged from 0.4% to 2.4%. In the case of the most flexible specimens, MEB underestimated the experimental results, while FEA led to higher retraction. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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17 pages, 8848 KiB

Open AccessArticle

Effects of Post-UV-Curing on the Flexural and Absorptive Behaviour of FDM-3D-Printed Poly(lactic acid) Parts

by Tarkan Akderya

Polymers 2023, 15(2), 348; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15020348 - 09 Jan 2023

Cited by 1 | Viewed by 1241

Abstract

In this study, the effects of the post-ultraviolet-curing process on the flexural, absorptive, and morphological properties of poly(lactic acid) specimens produced using a fused deposition modelling technique 3D printer were experimentally investigated. In this direction, 15, 30, 45, and 60 min post-UV-curing processes were applied to poly(lactic acid) three-point bending and absorption specimens produced at 190 and 200 °C. Three-point bending tests and morphological analyses were applied after the post-ultraviolet-curing process, and absorption tests were applied by immersing the post-ultraviolet-cured specimens in a distilled water bath for 1-, 3-day, and 1-, 2-, and 4-week exposure times. The changes in flexural strain properties for each experimental parameter were also simulated by the computer-aided finite element analysis and compared with the experimental results. It was observed that the post-ultraviolet-curing process increased the flexural strength of the poly(lactic acid) specimens produced at both 190 and 200 °C with the same increasing trend up to 30 min of exposure, and the most significant increase was determined in the specimens that were subjected to post-ultraviolet-curing for 30 min. Although the flexural strengths of the post-ultraviolet-cured specimens were higher than the non-cured specimens in all conditions, it was detected that they tended to decrease after 30 min. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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21 pages, 7676 KiB

Open AccessArticle

Effects of Laser Power and Hatch Orientation on Final Properties of PA12 Parts Produced by Selective Laser Sintering

by Anouar El Magri, Salah Eddine Bencaid, Hamid Reza Vanaei and Sébastien Vaudreuil

Polymers 2022, 14(17), 3674; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14173674 - 04 Sep 2022

Cited by 26 | Viewed by 2699

Abstract

Poly(dodecano-12-lactam) (commercially known as polyamide “PA12”) is one of the most resourceful materials used in the selective laser sintering (SLS) process due to its chemical and physical properties. The present work examined the influence of two SLS parameters, namely, laser power and hatch orientation, on the tensile, structural, thermal, and morphological properties of the fabricated PA12 parts. The main objective was to evaluate the suitable laser power and hatching orientation with respect to obtaining better final properties. PA12 powders and SLS-printed parts were assessed through their particle size distributions, X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), a scanning electron microscope (SEM), and their tensile properties. The results showed that the significant impact of the laser power while hatching is almost unnoticeable when using a high laser power. A more significant condition of the mechanical properties is the uniformity of the powder bed temperature. Optimum factor levels were achieved at 95% laser power and parallel/perpendicular hatching. Parts produced with the optimized SLS parameters were then subjected to an annealing treatment to induce a relaxation of the residual stress and to enhance the crystallinity. The results showed that annealing the SLS parts at 170 °C for 6 h significantly improved the thermal, structural, and tensile properties of 3D-printed PA12 parts. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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27 pages, 7881 KiB

Open AccessArticle

Strain Release Behaviour during Crack Growth of a Polymeric Beam under Elastic Loads for Self-Healing

by Mohammed Dukhi Almutairi, Sultan Saleh Alnahdi and Muhammad A. Khan

Polymers 2022, 14(15), 3102; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14153102 - 30 Jul 2022

Cited by 2 | Viewed by 1492

Abstract

The response of polymeric beams made of Acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) in the form of 3D printed beams is investigated to test their elastic and plastic responses under different bending loads. Two types of 3D printed beams were designed to test their elastic and plastic responses under different bending loads. These responses were used to develop an origami capsule-based novel self-healing mechanism that can be triggered by crack propagation due to strain release in a structure. Origami capsules of TPU in the form of a cross with four small beams, either folded or elastically deformed, were embedded in a simple ABS beam. Crack propagation in the ABS beam released the strain, and the TPU capsule unfolded with the arms of the cross in the direction of the crack path, and this increased the crack resistance of the ABS beam. This increase in the crack resistance was validated in a delamination test of a double cantilever specimen under quasi-static load conditions. Repeated test results demonstrated the effect of self-healing on structural crack growth. The results show the potential of the proposed self-healing mechanism as a novel contribution to existing practices which are primarily based on external healing agents. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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12 pages, 25717 KiB

Open AccessArticle

Piezoresistive Properties of 3D-Printed Polylactic Acid (PLA) Nanocomposites

by Razieh Hashemi Sanatgar, Aurélie Cayla, Jinping Guan, Guoqiang Chen, Vincent Nierstrasz and Christine Campagne

Polymers 2022, 14(15), 2981; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14152981 - 22 Jul 2022

Cited by 5 | Viewed by 1546

Abstract

An increasing interest is focused on the application of 3D printing for sensor manufacturing. Using 3D printing technology offers a new approach to the fabrication of sensors that are both geometrically and functionally complex. This work presents the analysis of the 3D-printed thermoplastic nanocomposites compress under the applied force. The response for the corresponding resistance changes versus applied load is obtained to evaluate the effectiveness of the printed layer as a pressure/force sensor. Multi-walled carbon nanotubes (MWNT) and high-structured carbon black (Ketjenblack) (KB) in the polylactic acid (PLA) matrix were extruded to develop 3D-printable filaments. The electrical and piezoresistive behaviors of the created 3D-printed layers were investigated. The percolation threshold of MWNT and KB 3D-printed layers are 1 wt.% and 4 wt.%, respectively. The PLA/1 wt.% MWNT 3D-printed layers with 1 mm thickness exhibit a negative pressure coefficient (NPC) characterized by a decrease of about one decade in resistance with increasing compressive loadings up to 18 N with a maximum strain up to about 16%. In the cyclic mode with a 1 N/min force rate, the PLA/1 wt.% MWNT 3D-printed layers showed good performance with the piezoresistive coefficient or gauge factor (G) of 7.6 obtained with the amplitude of the piezoresistive response (A_r) of about -0.8. KB composites could not show stable piezoresistive responses in a cyclic mode. However, under high force rate compression, the PLA/4 wt.% KB 3D-printed layers led to responses of large sensitivity (A_r = −0.90) and were exempt from noise with a high value of G = 47.6 in the first cycle, which is a highly efficient piezoresistive behavior. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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12 pages, 4396 KiB

Open AccessCommunication

Characterization of 3D Printed Metal-PLA Composite Scaffolds for Biomedical Applications

by Irene Buj-Corral, Héctor Sanz-Fraile, Anna Ulldemolins, Aitor Tejo-Otero, Alejandro Domínguez-Fernández, Isaac Almendros and Jorge Otero

Polymers 2022, 14(13), 2754; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14132754 - 05 Jul 2022

Cited by 20 | Viewed by 2877

Abstract

Three-dimensional printing is revolutionizing the development of scaffolds due to their rapid-prototyping characteristics. One of the most used techniques is fused filament fabrication (FFF), which is fast and compatible with a wide range of polymers, such as PolyLactic Acid (PLA). Mechanical properties of the 3D printed polymeric scaffolds are often weak for certain applications. A potential solution is the development of composite materials. In the present work, metal-PLA composites have been tested as a material for 3D printing scaffolds. Three different materials were tested: copper-filled PLA, bronze-filled PLA, and steel-filled PLA. Disk-shaped samples were printed with linear infill patterns and line spacing of 0.6, 0.7, and 0.8 mm, respectively. The porosity of the samples was measured from cross-sectional images. Biocompatibility was assessed by culturing Human Bone Marrow-Derived Mesenchymal Stromal on the surface of the printed scaffolds. The results showed that, for identical line spacing value, the highest porosity corresponded to bronze-filled material and the lowest one to steel-filled material. Steel-filled PLA polymers showed good cytocompatibility without the need to coat the material with biomolecules. Moreover, human bone marrow-derived mesenchymal stromal cells differentiated towards osteoblasts when cultured on top of the developed scaffolds. Therefore, it can be concluded that steel-filled PLA bioprinted parts are valid scaffolds for bone tissue engineering. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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17 pages, 2881 KiB

Open AccessArticle

Modeling Impact Mechanics of 3D Helicoidally Architected Polymer Composites Enabled by Additive Manufacturing for Lightweight Silicon Photovoltaics Technology

by Arief Suriadi Budiman, Rahul Sahay, Komal Agarwal, Rayya Fajarna, Fergyanto E. Gunawan, Avinash Baji and Nagarajan Raghavan

Polymers 2022, 14(6), 1228; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14061228 - 18 Mar 2022

Cited by 2 | Viewed by 2051

Abstract

When silicon solar cells are used in the novel lightweight photovoltaic (PV) modules using a sandwich design with polycarbonate sheets on both the front and back sides of the cells, they are much more prone to impact loading, which may be prevalent in four-season countries during wintertime. Yet, the lightweight PV modules have recently become an increasingly important development, especially for certain segments of the renewable energy markets all over the world—such as exhibition halls, factories, supermarkets, farms, etc.—including in countries with harsh hailstorms during winter. Even in the standard PV module design using glass as the front sheet, the silicon cells inside remain fragile and may be prone to impact loading. This impact loading has been widely known to lead to cracks in the silicon solar cells that over an extended period of time may significantly degrade performance (output power). In our group’s previous work, a 3D helicoidally architected fiber-based polymer composite (enabled by an electrospinning-based additive manufacturing methodology) was found to exhibit excellent impact resistance—absorbing much of the energy from the impact load—such that the silicon solar cells encapsulated on both sides by this material breaks only at significantly higher impact load/energy, compared to when a standard, commercial PV encapsulant material was used. In the present study, we aim to use numerical simulation and modeling to enhance our understanding of the stress distribution and evolution during impact loading on such helicoidally arranged fiber-based composite materials, and thus the damage evolution and mechanisms. This could further aid the implementation of the lightweight PV technology for the unique market needs, especially in countries with extreme winter seasons. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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14 pages, 27091 KiB

Open AccessArticle

Clinical Application of 3D-Printed Patient-Specific Polycaprolactone/Beta Tricalcium Phosphate Scaffold for Complex Zygomatico-Maxillary Defects

by Woo-Shik Jeong, Young-Chul Kim, Jae-Cheong Min, Ho-Jin Park, Eun-Ju Lee, Jin-Hyung Shim and Jong-Woo Choi

Polymers 2022, 14(4), 740; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14040740 - 14 Feb 2022

Cited by 20 | Viewed by 3186

Abstract

(1) Background: In the present study, we evaluated the efficacy of a 3D-printed, patient-specific polycaprolactone/beta tricalcium phosphate (PCL/β-TCP) scaffold in the treatment of complex zygomatico-maxillary defects. (2) Methods: We evaluated eight patients who underwent immediate or delayed maxillary reconstruction with patient-specific PCL implants between December 2019 and June 2021. The efficacy of these techniques was assessed using the volume and density analysis of computed tomography data obtained before surgery and six months after surgery. (3) Results: Patients underwent maxillary reconstruction with the 3D-printed PCL/β-TCP scaffold based on various reconstructive techniques, including bone graft, fasciocutaneous free flaps, and fat graft. In the volume analysis, satisfactory volume conformity was achieved between the preoperative simulation and actual implant volume with a mean volume conformity of 79.71%, ranging from 70.89% to 86.31%. The ratio of de novo bone formation to total implant volume (bone volume fraction) was satisfactory with a mean bone fraction volume of 23.34%, ranging from 7.81% to 66.21%. Mean tissue density in the region of interest was 188.84 HU, ranging from 151.48 HU to 291.74 HU. (4) Conclusions: The combined use of the PCL/β-TCP scaffold with virtual surgical simulation and 3D printing techniques may replace traditional non-absorbable implants in the future owing to its accuracy and biocompatible properties. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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16 pages, 6225 KiB

Open AccessArticle

Effect of Architected Structural Members on the Viscoelastic Response of 3D Printed Simple Cubic Lattice Structures

by Ahmed Abusabir, Muhammad A. Khan, Muhammad Asif and Kamran A. Khan

Polymers 2022, 14(3), 618; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14030618 - 05 Feb 2022

Cited by 10 | Viewed by 2914

Abstract

Three-dimensional printed polymeric lattice structures have recently gained interests in several engineering applications owing to their excellent properties such as low-density, energy absorption, strength-to-weight ratio, and damping performance. Three-dimensional (3D) lattice structure properties are governed by the topology of the microstructure and the base material that can be tailored to meet the application requirement. In this study, the effect of architected structural member geometry and base material on the viscoelastic response of 3D printed lattice structure has been investigated. The simple cubic lattice structures based on plate-, truss-, and shell-type structural members were used to describe the topology of the cellular solid. The proposed lattice structures were fabricated with two materials, i.e., PLA and ABS using the material extrusion (MEX) process. The quasi-static compression response of lattice structures was investigated, and mechanical properties were obtained. Then, the creep, relaxation and cyclic viscoelastic response of the lattice structure were characterized. Both material and topologies were observed to affect the mechanical properties and time-dependent behavior of lattice structure. Plate-based lattices were found to possess highest stiffness, while the highest viscoelastic behavior belongs to shell-based lattices. Among the studied lattice structures, we found that the plate-lattice is the best candidate to use as a creep-resistant LS and shell-based lattice is ideal for damping applications under quasi-static loading conditions. The proposed analysis approach is a step forward toward understanding the viscoelastic tolerance design of lattice structures. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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22 pages, 8298 KiB

Open AccessArticle

Effect of Printing Process Parameters on the Shape Transformation Capability of 3D Printed Structures

by Matej Pivar, Diana Gregor-Svetec and Deja Muck

Polymers 2022, 14(1), 117; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14010117 - 29 Dec 2021

Cited by 14 | Viewed by 3568

Abstract

The aim of our research was to investigate and optimise the main 3D printing process parameters that directly or indirectly affect the shape transformation capability and to determine the optimal transformation conditions to achieve predicted extent, and accurate and reproducible transformations of 3D printed, shape-changing two-material structures based on PLA and TPU. The shape-changing structures were printed using the FDM technology. The influence of each printing parameter that affects the final printability of shape-changing structures is presented and studied. After optimising the 3D printing process parameters, the extent, accuracy and reproducibility of the shape transformation performance for four-layer structures were analysed. The shape transformation was performed in hot water at different activation temperatures. Through a careful selection of 3D printing process parameters and transformation conditions, the predicted extent, accuracy and good reproducibility of shape transformation for 3D printed structures were achieved. The accurate deposition of filaments in the layers was achieved by adjusting the printing speed, flow rate and cooling conditions of extruded filaments. The shape transformation capability of 3D printed structures with a defined shape and defined active segment dimensions was influenced by the relaxation of compressive and tensile residual stresses in deposited filaments in the printed layers of the active material and different activation temperatures of the transformation. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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14 pages, 22602 KiB

Open AccessArticle

3D Bioprinting of Polycaprolactone-Based Scaffolds for Pulp-Dentin Regeneration: Investigation of Physicochemical and Biological Behavior

by Zohre Mousavi Nejad, Ali Zamanian, Maryam Saeidifar, Hamid Reza Vanaei and Mehdi Salar Amoli

Polymers 2021, 13(24), 4442; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13244442 - 17 Dec 2021

Cited by 38 | Viewed by 5064

Abstract

In this study, two structurally different scaffolds, a polycaprolactone (PCL)/45S5 Bioglass (BG) composite and PCL/hyaluronic acid (HyA) were fabricated by 3D printing technology and were evaluated for the regeneration of dentin and pulp tissues, respectively. Their physicochemical characterization was performed by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle, and compressive strength tests. The results indicated that the presence of BG in the PCL/BG scaffolds promoted the mechanical properties, surface roughness, and bioactivity. Besides, a surface treatment of the PCL scaffold with HyA considerably increased the hydrophilicity of the scaffolds which led to an enhancement in cell adhesion. Furthermore, the gene expression results showed a significant increase in expression of odontogenic markers, e.g., dentin sialophosphoprotein (DSPP), osteocalcin (OCN), and dentin matrix protein 1 (DMP-1) in the presence of both PCL/BG and PCL/HyA scaffolds. Moreover, to examine the feasibility of the idea for pulp-dentin complex regeneration, a bilayer PCL/BG-PCL/HyA scaffold was successfully fabricated and characterized by FESEM. Based on these results, it can be concluded that PCL/BG and PCL/HyA scaffolds have great potential for promoting hDPSC adhesion and odontogenic differentiation. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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Review

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19 pages, 1960 KiB

Open AccessReview

Additive Manufacturing of Polyolefins

by Fotis Christakopoulos, Paul M. H. van Heugten and Theo A. Tervoort

Polymers 2022, 14(23), 5147; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14235147 - 26 Nov 2022

Cited by 8 | Viewed by 2420

Abstract

Polyolefins are semi-crystalline thermoplastic polymers known for their good mechanical properties, low production cost, and chemical resistance. They are amongst the most commonly used plastics, and many polyolefin grades are regarded as engineering polymers. The two main additive manufacturing techniques that can be used to fabricate 3D-printed parts are fused filament fabrication and selective laser sintering. Polyolefins, like polypropylene and polyethylene, can, in principle, be processed with both these techniques. However, the semi-crystalline nature of polyolefins adds complexity to the use of additive manufacturing methods compared to amorphous polymers. First, the crystallization process results in severe shrinkage upon cooling, while the processing temperature and cooling rate affect the mechanical properties and mesoscopic structure of the fabricated parts. In addition, for ultra-high-molecular weight polyolefins, limited chain diffusion is a major obstacle to achieving proper adhesion between adjunct layers. Finally, polyolefins are typically apolar polymers, which reduces the adhesion of the 3D-printed part to the substrate. Notwithstanding these difficulties, it is clear that the successful processing of polyolefins via additive manufacturing techniques would enable the fabrication of high-end engineering products with enormous design flexibility. In addition, additive manufacturing could be utilized for the increased recycling of plastics. This manuscript reviews the work that has been conducted in developing experimental protocols for the additive manufacturing of polyolefins, presenting a comparison between the different approaches with a focus on the use of polyethylene and polypropylene grades. This review is concluded with an outlook for future research to overcome the current challenges that impede the addition of polyolefins to the standard palette of materials processed through additive manufacturing. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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16 pages, 5649 KiB

Open AccessReview

3D Printed and Conventional Membranes—A Review

by Baye Gueye Thiam, Anouar El Magri, Hamid Reza Vanaei and Sébastien Vaudreuil

Polymers 2022, 14(5), 1023; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14051023 - 03 Mar 2022

Cited by 38 | Viewed by 4463

Abstract

Polymer membranes are central to the proper operation of several processes used in a wide range of applications. The production of these membranes relies on processes such as phase inversion, stretching, track etching, sintering, or electrospinning. A novel and competitive strategy in membrane production is the use of additive manufacturing that enables the easier manufacture of tailored membranes. To achieve the future development of better membranes, it is necessary to compare this novel production process to that of more conventional techniques, and clarify the advantages and disadvantages. This review article compares a conventional method of manufacturing polymer membranes to additive manufacturing. A review of 3D printed membranes is also done to give researchers a reference guide. Membranes from these two approaches were compared in terms of cost, materials, structures, properties, performance. and environmental impact. Results show that very few membrane materials are used as 3D-printed membranes. Such membranes showed acceptable performance, better structures, and less environmental impact compared with those of conventional membranes. Full article

(This article belongs to the Special Issue Polymers and Their Application in 3D Printing)

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