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Process–Structure–Properties in Polymer Additive Manufacturing II

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

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 38365

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Dr. Swee Leong Sing

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Guest Editor

Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore
Interests: additive manufacturing; 3D printing; 3D bioprinting; laser–material interactions; laser-based advanced manufacturing
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Wai Yee Yeong

E-Mail Website
Guest Editor

Singapore Centre for 3D Printing, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
Interests: additive manufacturing; 3D printing; 3D bioprinting
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Additive manufacturing (AM) methods have grown and evolved rapidly in recent years. AM for polymers particularly exciting and has great potential in transformative and translational research in many fields, such as biomedical, aerospace, and even electronics. Current methods for polymer AM include material extrusion, material jetting, vat polymerization, and powder bed fusion.

In this Special Issue, state-of-the-art reviews and current research results, which focus on the process–structure–properties relationships in polymer additive manufacturing, will be reported. These include, but is not limited to, assessing the effect of process parameters, post-processing, and characterization techniques. Submissions related to novel applications, designs, processes or characterization methods are also welcomed.

Contributions focused on polymer additive manufacturing in any of the following topics are of particular interest:

Materials, processes and machines;
Process monitoring, modeling, and control;
Design for additive manufacturing;
Data analytics, machine learning and artificial intelligence applied to polymer additive manufacturing
Development of novel polymers for additive manufacturing;
New applications of polymers additive manufacturing in the industries.

Dr. Swee Leong Sing
Prof. Dr. Wai Yee Yeong
Guest Editors

Manuscript Submission Information

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

Additive manufacturing
3D printing
Machine learning
Artificial intelligence
Data analytics
Polymers
Mechanical properties
Microstructural analysis
Thermal properties

Related Special Issue

Advanced Manufacturing for Polymers in Polymers (24 articles)

Published Papers (11 papers)

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Editorial

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2 pages, 185 KiB

Open AccessEditorial

Recent Progress in Research of Additive Manufacturing for Polymers

by Swee Leong Sing and Wai Yee Yeong

Polymers 2022, 14(11), 2267; https://doi.org/10.3390/polym14112267 - 02 Jun 2022

Cited by 4 | Viewed by 1578

Abstract

Additive manufacturing (AM) methods have grown and evolved rapidly in recent years [...] Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

Research

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17 pages, 8208 KiB

Open AccessArticle

Low Temperature Powder Bed Fusion of Polymers by Means of Fractal Quasi-Simultaneous Exposure Strategies

by Samuel Schlicht, Sandra Greiner and Dietmar Drummer

Polymers 2022, 14(7), 1428; https://doi.org/10.3390/polym14071428 - 31 Mar 2022

Cited by 8 | Viewed by 2953

Abstract

Powder Bed Fusion of Polymers (PBF-LB/P) is a layer-wise additive manufacturing process that predominantly relies on the quasi-isothermal processing of semi-crystalline polymers, inherently limiting the spectrum of polymers suitable for quasi-isothermal PBF. Within the present paper, a novel approach for extending the isothermal processing window towards significantly lower temperatures by applying the quasi-simultaneous laser-based exposure of fractal scan paths is proposed. The proposed approach is based on the temporal and spatial discretization of the melting and subsequent crystallization of semi-crystalline thermoplastics, hence allowing for the mesoscale compensation of crystallization shrinkage of distinct segments. Using thermographic monitoring, a homogenous temperature increase of discrete exposed sub-segments, limited thermal interference of distinct segments, and the resulting avoidance of curling and warping can be observed. Manufactured parts exhibit a dense and lamellar part morphology with a nano-scale semi-crystalline structure. The presented approach represents a novel methodology that allows for significantly reducing energy consumption, process preparation times and temperature-induced material aging in PBF-LB/P while representing the foundation for the processing of novel, thermo-sensitive material systems in PBF-LB/P. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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11 pages, 22692 KiB

Open AccessArticle

Analysis of UV Curing Strategy on Reaction Heat Control and Part Accuracy for Additive Manufacturing

by Fengze Jiang and Dietmar Drummer

Polymers 2022, 14(4), 759; https://doi.org/10.3390/polym14040759 - 15 Feb 2022

Cited by 5 | Viewed by 2904

Abstract

In this research, the relationship between the curing strategies and geometrical accuracy of parts under UV light was investigated. An IR camera was utilized to monitor the process using different combinations of photosensitive resin and curing strategies. The influences of curing strategies on different material compositions were studied with single-factor analysis. With the different exposure frequencies of the UV light, the peak temperature was adjusted to avoid overheating. The three-dimensional geometry of casting tensile bars was measured to investigate the shrinkage and warpage during the curing process. Different material compositions were also selected to study the effects of the maximum temperature on the shrinkage of the parts. The findings of this work show that, with the same amount of energy input, a more fragmented exposure allows for a more controllable max temperature, while one-time exposure leads to a high temperature during the process. With the decrease of the released heat from the reaction, the shrinkage of the casting part has a slightly increasing tendency. Moreover, the warpage of the parts decreased drastically with the decrease of temperature. The addition of fillers enhances the control over temperature and increases the geometrical accuracy. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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19 pages, 6971 KiB

Open AccessArticle

New Methodology for Evaluating Surface Quality of Experimental Aerodynamic Models Manufactured by Polymer Jetting Additive Manufacturing

by Razvan Udroiu

Polymers 2022, 14(3), 371; https://doi.org/10.3390/polym14030371 - 18 Jan 2022

Cited by 9 | Viewed by 1862

Abstract

The additive manufacturing (AM) applications have attracted a great deal of interest with regard to experimental aerodynamic studies. There is a need for a universal roughness scale that characterizes different materials used in aerodynamic research. The main purpose of this paper is identification of the potential of a material jetting AM process to produce accurate aerodynamic surfaces. A new methodology to evaluate the roughness of aerodynamic profiles (airfoils) was proposed. A very short-span wing artifact for preliminary tests and a long-span wing model were proposed for design of experiments. Different artifacts orientations were analyzed, maintaining the same surface quality on the upper and lower surface of the wing. A translucent polymeric resin was used for samples manufacturing by polymer jetting (PolyJet) technology. The effects of main factors on the surface roughness of the wing were investigated using the statistical design of experiments. Three interest locations, meaning the leading-edge, central, and trailing-edge zones, on the upper and lower surfaces of the airfoil were considered. The best results were obtained for a sample oriented at XY on the build platform, in matte finish type, with a mean Ra roughness in the range of 2 to 3.5 μm. Microscopy studies were performed to analyze and characterize the surfaces of the wing samples on their different zones. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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11 pages, 2909 KiB

Open AccessArticle

Comparison between Tests and Simulations Regarding Bending Resistance of 3D Printed PLA Structures

by Dorin-Ioan Catana, Mihai-Alin Pop and Denisa-Iulia Brus

Polymers 2021, 13(24), 4371; https://doi.org/10.3390/polym13244371 - 14 Dec 2021

Cited by 5 | Viewed by 2326

Abstract

Additive manufacturing is one of the technologies that is beginning to be used in new fields of parts production, but it is also a technology that is constantly evolving, due to the advances made by researchers and printing equipment. The paper presents how, by using the simulation process, the geometry of the 3D printed structures from PLA and PLA-Glass was optimized at the bending stress. The optimization aimed to reduce the consumption of filament (material) simultaneously with an increase in the bending resistance. In addition, this paper demonstrates that the simulation process can only be applied with good results to 3D printed structures when their mechanical properties are known. The inconsistency of printing process parameters makes the 3D printed structures not homogeneous and, consequently, the occurrence of errors between the test results and those of simulations become natural and acceptable. The mechanical properties depend on the values of the printing process parameters and the printing equipment because, in the case of 3D printing, it is necessary for each combination of parameters to determine their mechanical properties through specific tests. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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13 pages, 2426 KiB

Open AccessArticle

Biodegradable PGA/PBAT Blends for 3D Printing: Material Performance and Periodic Minimal Surface Structures

by Zihui Zhang, Fengtai He, Bo Wang, Yiping Zhao, Zhiyong Wei, Hao Zhang and Lin Sang

Polymers 2021, 13(21), 3757; https://doi.org/10.3390/polym13213757 - 30 Oct 2021

Cited by 20 | Viewed by 3949

Abstract

Biodegradable polymers have been rapidly developed for alleviating excessive consumption of non-degradable plastics. Additive manufacturing is also a green energy-efficiency and environment-protection technique to fabricate complicated structures. Herein, biodegradable polyesters, polyglycolic acid (PGA) and poly (butyleneadipate-co-terephthalate) (PBAT) were blended and developed into feedstock for 3D printing. Under a set of formulations, PGA/PBAT blends exhibited a tailored stiffness-toughness mechanical performance. Then, PGA/PBAT (85/15 in weight ratio) with good thermal stability and mechanical property were extruded into filaments with a uniform wire diameter. Mechanical testing clearly indicated that FDM 3D-printed exhibited comparable tensile, flexural and impact properties with injection-molded samples of PGA/PBAT (85/15). Furthermore, uniform and graded Diamond-Triply Periodic Minimal Surfaces (D-TPMS) structures were designed and successfully manufactured via the fused deposition modeling (FDM) technique. Computer tomography (CT) was employed to confirm the internal three-dimensional structures. The compressive test results showed that PGA/PBAT (85/15) D-surface structures bear better load-carrying capacity than that of neat PGA, giving an advantage of energy absorption. Additionally, typical industrial parts were manufactured with excellent dimension-stability, no-wrapping and fine quality. Collectively, biodegradable PGA/PBAT material with good printability has great potentials in application requiring stiffer structures. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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21 pages, 9920 KiB

Open AccessArticle

Mechanical Properties of PolyJet 3D-Printed Composites Inspired by Space-Filling Peano Curves

by Changlang Wu, Truong Tho Do and Phuong Tran

Polymers 2021, 13(20), 3516; https://doi.org/10.3390/polym13203516 - 13 Oct 2021

Cited by 8 | Viewed by 2758

Abstract

This paper proposes a design of novel composite materials inspired by the Peano curve and manufactured using PolyJet 3D printing technology with Agilus30 (flexible phase) and VeroMagentaV (rigid phase) materials. Mechanical properties were evaluated through tensile and compression tests. The general rule of mixture (ROM) for composites was employed to approximate the tensile properties of the hybrid materials and compare them to the experimental results. The effect of reinforcement alignments and different hierarchies are discussed. The results indicated that the 5% inclusion of the Peano reinforcement in tensile samples contributed to the improvement in the elastic modulus by up to 6 MPa, but provided no obvious enhancement in ultimate tensile strength. Additionally, compressive strengths between 2 MPa and 6 MPa were observed for compression cubes with first-order reinforcement, while lower values around 2 MPa were found for samples with second-order reinforcement. That is to say, the first-order reinforcement has been demonstrated more effectively than the second-order reinforcement, given the same reinforcement volume fraction of 10% in compression cubes. Different second-order designs exhibited slightly different mechanical properties based on the ratio of reinforcement parallel to the loading direction. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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20 pages, 3099 KiB

Open AccessArticle

Investigating the Potential Plasticizing Effect of Di-Carboxylic Acids for the Manufacturing of Solid Oral Forms with Copovidone and Ibuprofen by Selective Laser Sintering

by Yanis Abdelhamid Gueche, Noelia M. Sanchez-Ballester, Bernard Bataille, Adrien Aubert, Jean-Christophe Rossi and Ian Soulairol

Polymers 2021, 13(19), 3282; https://doi.org/10.3390/polym13193282 - 26 Sep 2021

Cited by 5 | Viewed by 2021

Abstract

In selective laser sintering (SLS), the heating temperature is a critical parameter for printability but can also be deleterious for the stability of active ingredients. This work aims to explore the plasticizing effect of di-carboxylic acids on reducing the optimal heating temperature (OHT) of polymer powder during SLS. First, mixtures of copovidone and di-carboxylic acids (succinic, fumaric, maleic, malic and tartaric acids) as well as formulations with two forms of ibuprofen (acid and sodium salt) were prepared to sinter solid oral forms (SOFs), and their respective OHT was determined. Plasticization was further studied by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Following this, the printed SOFs were characterized (solid state, weight, hardness, disintegration time, drug content and release). It was found that all acids (except tartaric acid) reduced the OHT, with succinic acid being the most efficient. In the case of ibuprofen, only the acid form demonstrated a plasticizing effect. DSC and FTIR corroborated these observations showing a decrease in the glass transition temperature and the presence of interactions, respectively. Furthermore, the properties of the sintered SOFs were not affected by plasticization and the API was not degraded in all formulations. In conclusion, this study is a proof-of-concept that processability in SLS can improve with the use of di-carboxylic acids. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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16 pages, 2381 KiB

Open AccessArticle

Mechanical Properties and In Vitro Evaluation of Thermoplastic Polyurethane and Polylactic Acid Blend for Fabrication of 3D Filaments for Tracheal Tissue Engineering

by Asmak Abdul Samat, Zuratul Ain Abdul Hamid, Mariatti Jaafar and Badrul Hisham Yahaya

Polymers 2021, 13(18), 3087; https://doi.org/10.3390/polym13183087 - 13 Sep 2021

Cited by 18 | Viewed by 3085

Abstract

Surgical reconstruction of extensive tracheal lesions is challenging. It requires a mechanically stable, biocompatible, and nontoxic material that gradually degrades. One of the possible solutions for overcoming the limitations of tracheal transplantation is a three-dimensional (3D) printed tracheal scaffold made of polymers. Polymer blending is one of the methods used to produce material for a trachea scaffold with tailored characteristics. The purpose of this study is to evaluate the mechanical and in vitro properties of a thermoplastic polyurethane (TPU) and polylactic acid (PLA) blend as a potential material for 3D printed tracheal scaffolds. Both materials were melt-blended using a single screw extruder. The morphologies (as well as the mechanical and thermal characteristics) were determined via scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, tensile test, and Differential Scanning calorimetry (DSC). The samples were also evaluated for their water absorption, in vitro biodegradability, and biocompatibility. It is demonstrated that, despite being not miscible, TPU and PLA are biocompatible, and their promising properties are suitable for future applications in tracheal tissue engineering. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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16 pages, 5800 KiB

Open AccessArticle

Development and Characterization of Field Structured Magnetic Composites

by Balakrishnan Nagarajan, Yingnan Wang, Maryam Taheri, Simon Trudel, Steven Bryant, Ahmed Jawad Qureshi and Pierre Mertiny

Polymers 2021, 13(17), 2843; https://doi.org/10.3390/polym13172843 - 24 Aug 2021

Cited by 8 | Viewed by 2230

Abstract

Polymer composites containing ferromagnetic fillers are promising for applications relating to electrical and electronic devices. In this research, the authors modified an ultraviolet light (UV) curable prepolymer to additionally cure upon heating and validated a permanent magnet-based particle alignment system toward fabricating anisotropic magnetic composites. The developed dual-cure acrylate-based resin, reinforced with ferromagnetic fillers, was first tested for its ability to polymerize through UV and heat. Then, the magnetic alignment setup was used to orient magnetic particles in the dual-cure acrylate-based resin and a heat curable epoxy resin system in a polymer casting approach. The alignment setup was subsequently integrated with a material jetting 3D printer, and the dual-cure resin was dispensed and cured in-situ using UV, followed by thermal post-curing. The resulting magnetic composites were tested for their filler loading, microstructural morphology, alignment of the easy axis of magnetization, and degree of monomer conversion. Magnetic characterization was conducted using a vibrating sample magnetometer along the in-plane and out-of-plane directions to study anisotropic properties. This research establishes a methodology to combine magnetic field induced particle alignment along with a dual-cure resin to create anisotropic magnetic composites through polymer casting and additive manufacturing. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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Review

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19 pages, 2097 KiB

Open AccessReview

The State of the Art of Material Jetting—A Critical Review

by Orhan Gülcan, Kadir Günaydın and Aykut Tamer

Polymers 2021, 13(16), 2829; https://doi.org/10.3390/polym13162829 - 23 Aug 2021

Cited by 88 | Viewed by 11172

Abstract

Material jetting (MJ) technology is an additive manufacturing method that selectively cures liquid photopolymer to build functional parts. The use of MJ technology has increased in popularity and been adapted by different industries, ranging from biomedicine and dentistry to manufacturing and aviation, thanks to its advantages in printing parts with high dimensional accuracy and low surface roughness. To better understand the MJ technology, it is essential to address the capabilities, applications and the usage areas of MJ. Additionally, the comparison of MJ with alternative methods and its limitations need to be explained. Moreover, the parameters influencing the dimensional accuracy and mechanical properties of MJ printed parts should be stated. This paper aims to review these critical aspects of MJ manufacturing altogether to provide an overall insight into the state of the art of MJ. Full article

(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing II)

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