Polymers

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10 pages, 15135 KiB

Open AccessArticle

Electrospinning Nanofiber Mats with Magnetite Nanoparticles Using Various Needle-Based Techniques

by Al Mamun, Lilia Sabantina, Michaela Klöcker, Alexander Heide, Tomasz Blachowicz and Andrea Ehrmann

Polymers 2022, 14(3), 533; https://doi.org/10.3390/polym14030533 - 28 Jan 2022

Cited by 13 | Viewed by 3550

Abstract

Electrospinning can be used to produce nanofiber mats containing diverse nanoparticles for various purposes. Magnetic nanoparticles, such as magnetite (Fe₃O₄), can be introduced to produce magnetic nanofiber mats, e.g., for hyperthermia applications, but also for basic research of diluted [...] Read more.

Electrospinning can be used to produce nanofiber mats containing diverse nanoparticles for various purposes. Magnetic nanoparticles, such as magnetite (Fe₃O₄), can be introduced to produce magnetic nanofiber mats, e.g., for hyperthermia applications, but also for basic research of diluted magnetic systems. As the number of nanoparticles increases, however, the morphology and the mechanical properties of the nanofiber mats decrease, so that freestanding composite nanofiber mats with a high content of nanoparticles are hard to produce. Here we report on poly (acrylonitrile) (PAN) composite nanofiber mats, electrospun by a needle-based system, containing 50 wt% magnetite nanoparticles overall or in the shell of core–shell fibers, collected on a flat or a rotating collector. While the first nanofiber mats show an irregular morphology, the latter are quite regular and contain straight fibers without many beads or agglomerations. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveal agglomerations around the pure composite nanofibers and even, round core–shell fibers, the latter showing slightly increased fiber diameters. Energy dispersive X-ray spectroscopy (EDS) shows a regular distribution of the embedded magnetic nanoparticles. Dynamic mechanical analysis (DMA) reveals that mechanical properties are reduced as compared to nanofiber mats with smaller amounts of magnetic nanoparticles, but mats with 50 wt% magnetite are still freestanding. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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15 pages, 2750 KiB

Open AccessArticle

Vegetable Oil-Based Thiol-Ene/Thiol-Epoxy Resins for Laser Direct Writing 3D Micro-/Nano-Lithography

by Sigita Grauzeliene, Aukse Navaruckiene, Edvinas Skliutas, Mangirdas Malinauskas, Angels Serra and Jolita Ostrauskaite

Polymers 2021, 13(6), 872; https://doi.org/10.3390/polym13060872 - 12 Mar 2021

Cited by 30 | Viewed by 4891

Abstract

The use of renewable sources for optical 3D printing instead of petroleum-based materials is increasingly growing. Combinations of photo- and thermal polymerization in dual curing processes can enhance the thermal and mechanical properties of the synthesized thermosets. Consequently, thiol-ene/thiol-epoxy polymers were obtained by [...] Read more.

The use of renewable sources for optical 3D printing instead of petroleum-based materials is increasingly growing. Combinations of photo- and thermal polymerization in dual curing processes can enhance the thermal and mechanical properties of the synthesized thermosets. Consequently, thiol-ene/thiol-epoxy polymers were obtained by combining UV and thermal curing of acrylated epoxidized soybean oil and epoxidized linseed oil with thiols, benzene-1,3-dithiol and pentaerythritol tetra(3-mercaptopropionate). Thiol-epoxy reaction was studied by calorimetry. The changes of rheological properties were examined during UV, thermal and dual curing to select the most suitable formulations for laser direct writing (LDW). The obtained polymers were characterized by dynamic-mechanical thermal analysis, thermogravimetry, and mechanical testing. The selected dual curable mixture was tested in LDW 3D lithography for validating its potential in optical micro- and nano-additive manufacturing. The obtained results demonstrated the suitability of epoxidized linseed oil as a biobased alternative to bisphenol A diglycidyl ether in thiol-epoxy thermal curing reactions. Dual cured thermosets showed higher rigidity, tensile strength, and Young’s modulus values compared with UV-cured thiol-ene polymers and the highest thermal stability from all prepared polymers. LDW results proved their suitability for high resolution 3D printing—individual features reaching an unprecedented 100 nm for plant-based materials. Finally, the biobased resin was tested for thermal post-treatment and 50% feature downscaling was achieved. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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14 pages, 4378 KiB

Open AccessArticle

Physical and Chemical Properties Characterization of 3D-Printed Substrates Loaded with Copper-Nickel Nanowires

by Ely Dannier V-Niño, Quentin Lonne, Andrés Díaz Lantada, Enrique Mejía-Ospino, Hugo Armando Estupiñán Durán, Rafael Cabanzo Hernández, Gustavo Ramírez-Caballero and José Luis Endrino

Polymers 2020, 12(11), 2680; https://doi.org/10.3390/polym12112680 - 13 Nov 2020

Cited by 7 | Viewed by 2844

Abstract

This study deals with the laser stereolithography manufacturing feasibility of copper-nickel nanowire-loaded photosensitive resins. The addition of nanowires resulted in a novel resin suitable for additive manufacturing technologies based on layer-by-layer photopolymerization. The pure and nanowire-loaded resin samples were 3D printed in a [...] Read more.

This study deals with the laser stereolithography manufacturing feasibility of copper-nickel nanowire-loaded photosensitive resins. The addition of nanowires resulted in a novel resin suitable for additive manufacturing technologies based on layer-by-layer photopolymerization. The pure and nanowire-loaded resin samples were 3D printed in a similar way. Their morphological, mechanical, thermal, and chemical properties were characterized. X-ray computed tomography revealed that

0.06 vol %

of the composite resin was filled with nanowires forming randomly distributed aggregates. The increase of

57 %

in the storage modulus and

50 %

in the hardness when loading the resin with nanowire was attributed to the load transfer. Moreover, the decrease in the glass transition temperature from

57.9 ° C

to

52.8 ° C

in the polymeric matrix with nanowires evidenced a decrease in the cross-linking density, leading to a higher mobility of the polymer chains during glass transition. Consequently, this research demonstrates the successful dispersion and use of copper-nickel nanowires as a reinforcement material in a commercial resin for laser stereolithography. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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20 pages, 5532 KiB

Open AccessArticle

The Transferability and Design of Commercial Printer Settings in PLA/PBAT Fused Filament Fabrication

by Sisi Wang, Dagmar R. D’hooge, Lode Daelemans, Hesheng Xia, Karen De Clerck and Ludwig Cardon

Polymers 2020, 12(11), 2573; https://doi.org/10.3390/polym12112573 - 2 Nov 2020

Cited by 13 | Viewed by 2930

Abstract

In many fused filament fabrication (FFF) processes, commercial printers are used, but rarely are printer settings transferred from one commercial printer to the other to give similar final tensile part performance. Here, we report such translation going from the Felix 3.0 to Prusa [...] Read more.

In many fused filament fabrication (FFF) processes, commercial printers are used, but rarely are printer settings transferred from one commercial printer to the other to give similar final tensile part performance. Here, we report such translation going from the Felix 3.0 to Prusa i3 MK3 printer by adjusting the flow rate and overlap of strands, utilizing an in-house developed blend of polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). We perform a sensitivity analysis for the Prusa printer, covering variations in nozzle temperature, nozzle diameter, layer thickness, and printing speed (T_nozzle, d_nozzle, LT, and v_print), aiming at minimizing anisotropy and improving interlayer bonding. Higher mass, larger width, and thickness are obtained with larger d_nozzle, lower v_print, higher LT, and higher T_nozzle. A higher v_print results in less tensile strain at break, but it remains at a high strain value for samples printed with d_nozzle equal to 0.5 mm. v_print has no significant effect on the tensile modulus and tensile and impact strength of the samples. If LT is fixed, an increased d_nozzle is beneficial for the tensile strength, ductility, and impact strength of the printed sample due to better bonding from a wider raster structure, while an increased LT leads to deterioration of mechanical properties. If the ratio d_nozzle/LT is greater than 2, a good tensile performance is obtained. An improved T_nozzle leads to a sufficient flow of material, contributing to the performance of the printed device. The considerations brought forward result in a deeper understanding of the FFF process and offer guidance about parameter selection. The optimal d_nozzle/v_print/LT/T_nozzle combination is 0.5 mm/120 mm s⁻¹/0.15 mm/230 °C. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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12 pages, 6110 KiB

Open AccessArticle

3D Printing of Oil Paintings Based on Material Jetting and Its Reduction of Staircase Effect

by Jiangping Yuan, Chen Chen, Danyang Yao and Guangxue Chen

Polymers 2020, 12(11), 2536; https://doi.org/10.3390/polym12112536 - 29 Oct 2020

Cited by 24 | Viewed by 3846

Abstract

Material jetting is a high-precision and fast 3D printing technique for color 3D objects reproduction, but it also suffers from color accuracy and jagged issues. The UV inks jetting processes based on the polymer jetting principle have been studied from printing materials regarding [...] Read more.

Material jetting is a high-precision and fast 3D printing technique for color 3D objects reproduction, but it also suffers from color accuracy and jagged issues. The UV inks jetting processes based on the polymer jetting principle have been studied from printing materials regarding the parameters in the default layer order, which is prone to staircase effects. In this work, utilizing the Mimaki UV inks jetting system with a variable layer thickness, a new framework to print a photogrammetry-based oil painting 3D model has been proposed with the tunable coloring layer sequence to improve the jagged challenge between adjacent layers. Based on contour tracking, a height-rendering image of the oil painting model is generated, which is further segmented and pasted to the corresponding slicing layers to control the overall printing sequence of coloring layers and white layers. The final results show that photogrammetric models of oil paintings can be printed vividly by UV-curable color polymers, and that the proposed reverse-sequence printing method can significantly improve the staircase effect based on visual assessment and color difference. Finally, the case of polymer-based oil painting 3D printing provides new insights for optimizing color 3D printing processes based on other substrates and print accuracy to improve the corresponding staircase effect. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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14 pages, 3711 KiB

Open AccessArticle

Design and Synthesis of Free-Radical/Cationic Photosensitive Resin Applied for 3D Printer with Liquid Crystal Display (LCD) Irradiation

by Junyang Shan, Zijun Yang, Guoguang Chen, Yang Hu, Ying Luo, Xianming Dong, Wenxu Zheng and Wuyi Zhou

Polymers 2020, 12(6), 1346; https://doi.org/10.3390/polym12061346 - 15 Jun 2020

Cited by 30 | Viewed by 6073

Abstract

In this work, aiming at a UV-curing 3D printing process with liquid crystal display (LCD) irradiation, a novel free-radical/cationic hybrid photosensitive resin was designed and prepared. After testing, the results showed that the acrylate monomers could be polymerized through a free-radical mechanism, while [...] Read more.

In this work, aiming at a UV-curing 3D printing process with liquid crystal display (LCD) irradiation, a novel free-radical/cationic hybrid photosensitive resin was designed and prepared. After testing, the results showed that the acrylate monomers could be polymerized through a free-radical mechanism, while the epoxides were polymerized by a cationic curing mechanism. During the process of UV-curing, the acrylate and epoxide polymers were crosslinked and further locked together by non-covalent bonds. Therefore, an interpenetrating polymer network (IPN) structure could be formed through light-curing 3D-printing processes. Fourier transform infrared spectroscopy (FT-IR) revealed that the 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl formate and acrylic resin were both successfully involved in the UV-curing process. Furthermore, in order to make the 3D-printed objects cured completely, post-processing was of great importance. The results from the systematic study of the dynamic mechanical properties of the printed objects showed that the heating treatment process after UV irradiation was very necessary and favorable for the complete cationic polymerization of UV-6110 induced by Irgacure 261. The optimum heating treatment conditions were achieved at a temperature of 70 °C for 3 h. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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14 pages, 3840 KiB

Open AccessArticle

Influence of the Surface Modification of Calcium Carbonate on Polyamide 12 Composites

by Fabio Ippolito, Gunter Hübner, Tim Claypole and Patrick Gane

Polymers 2020, 12(6), 1295; https://doi.org/10.3390/polym12061295 - 5 Jun 2020

Cited by 15 | Viewed by 5978

Abstract

In previous investigations, it was found that the thermal properties of a polyamide 12 compound can be manipulated, using a designed filler, to improve the melting as well as crystallization behavior, determined for selective laser sintering. A common downside of the introduction of [...] Read more.

In previous investigations, it was found that the thermal properties of a polyamide 12 compound can be manipulated, using a designed filler, to improve the melting as well as crystallization behavior, determined for selective laser sintering. A common downside of the introduction of a non-flexing mineral filler is the reduction of the mechanical properties, such as ductility. This paper investigates the influence of content and surface modification of limestone on the mechanical properties. The aim is to understand the effect of an optimized coupling agent on the properties of a compound, containing polyamide 12 filled with 10 wt % of surface modified calcium carbonate. A range of four mineral filler modifications was chosen to investigate their coupling effect, namely 6-amino hexanoic acid, ε-caprolactam, l-arginine or glutamic acid. The in advance surface modified fillers were then each used in combination with the polyamide 12 in a twin-screw extrusion process. With an optimized surface modifying agent, the tensile strength as well as elongation at break can be improved in comparison with uncoated filler implementation, such that up to 60% of the loss of ductility and toughness of a final part when using an untreated filler could be regained using an optimized surface modifier at a correct amount. With the tested filler grade and the specific tested filler amount, the optimized amount of 6-amino hexanoic acid was approx. 2.5 mmol of treatment agent per 100 m² of CaCO₃. These found improvements in a twin-screw extruded polyamide 12 compound show the possible usage of modified calcium carbonate as a functional filler in additive manufacturing and can potentially be transferred in a subsequent investigation in the selective laser sintering process. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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11 pages, 2565 KiB

Open AccessEditor’s ChoiceArticle

Optimization and Quality Evaluation of the Interlayer Bonding Performance of Additively Manufactured Polymer Structures

by Patrick Striemann, Daniel Hülsbusch, Michael Niedermeier and Frank Walther

Polymers 2020, 12(5), 1166; https://doi.org/10.3390/polym12051166 - 19 May 2020

Cited by 25 | Viewed by 3296

Abstract

The application of additive manufacturing changes from prototypes to series production. In order to fulfill all requirements of series production, the process and the material characteristics must be known. The machine operator of additive manufacturing systems is both a component and a material [...] Read more.

The application of additive manufacturing changes from prototypes to series production. In order to fulfill all requirements of series production, the process and the material characteristics must be known. The machine operator of additive manufacturing systems is both a component and a material producer. Nevertheless, there is no standardized procedure for the manufacturing or testing of such materials. This includes the high degree of anisotropy of additively manufactured polymers via material extrusion. The interlayer bonding performance between two layers in the manufacturing direction z is the obvious weakness that needs to be improved. By optimizing this interlayer contact zone, the overall performance of the additively manufactured polymer is increased. This was achieved by process modification with an infrared preheating system (IPS) to keep the temperature of the interlayer contact zone above the glass transition temperature during the manufacturing process. Combining destructive and non-destructive testing methods, the process modification IPS was determined and evaluated by a systematic approach for characterizing the interlayer bonding performance. Thereby, tensile tests under quasi-static and cyclic loading were carried out on short carbon fiber-reinforced polyamide (SCFRP). In addition, micro-computed tomography and microscopic investigations were used to determine the process quality. The IPS increases the ultimate interlayer tensile strength by approx. 15% and shows a tendency to significantly improved the fatigue properties. Simultaneously, the analysis of the micro-computed tomography data shows a homogenization of the void distribution by using the IPS. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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16 pages, 4482 KiB

Open AccessArticle

Influence of Manufacturing Parameters and Post Processing on the Electrical Conductivity of Extrusion-Based 3D Printed Nanocomposite Parts

by Rubén Paz, Rocío Moriche, Mario Monzón and Joshua García

Polymers 2020, 12(4), 733; https://doi.org/10.3390/polym12040733 - 25 Mar 2020

Cited by 32 | Viewed by 3986

Abstract

The influence of manufacturing parameters of filament extrusion and extrusion-based Additive Manufacturing (AM), as well as different post processing techniques, on the electrical conductivity of 3D printed parts of graphene nanoplatelets (GNP)-reinforced acrylonitrile butadiene styrene (ABS) has been analyzed. The key role of [...] Read more.

The influence of manufacturing parameters of filament extrusion and extrusion-based Additive Manufacturing (AM), as well as different post processing techniques, on the electrical conductivity of 3D printed parts of graphene nanoplatelets (GNP)-reinforced acrylonitrile butadiene styrene (ABS) has been analyzed. The key role of the manufacturing parameters to obtain electrically conductive filaments and 3D printed parts has been demonstrated. Results have shown that an increase in extrusion speed, as well as lower land lengths, induces higher extrudate swelling, with the consequent reduction of the electrical conductivity. Additionally, filaments with lower diameter values, which result in a higher surface-to-cross-section ratio, have considerably lower electrical conductivities. These factors tune the values of the volume and surface electrical conductivity between 10⁻⁴–10⁰ S/m and 10⁻⁸–10⁻³ S/sq, respectively. The volume and surface electrical conductivity considerably diminished after 3D printing. They increased when using higher printing layer thickness and width and were ranging between 10⁻⁷–10⁻⁴ S/m and 10⁻⁸–10⁻⁵ S/sq, respectively. This is attributed to the higher cross section area of the individual printed lines. The effect of different post processing (acetone vapor polishing, plasma and neosanding, which is a novel finishing process) on 3D printed parts in morphology and surface electrical conductivity was also analyzed. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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15 pages, 17232 KiB

Open AccessArticle

Effect of PEW and CS on the Thermal, Mechanical, and Shape Memory Properties of UHMWPE

by Run Zhang, Suwei Wang, Jing Tian, Ke Chen, Ping Xue, Yihui Wu and Weimin Chou

Polymers 2020, 12(2), 483; https://doi.org/10.3390/polym12020483 - 21 Feb 2020

Cited by 20 | Viewed by 3923

Abstract

Modified ultra-high-molecular-weight polyethylene (UHMWPE) with calcium stearate (CS) and polyethylene wax (PEW) is a feasible method to improve the fluidity of materials because of the tense entanglement network formed by the extremely long molecular chains of UHMWPE, and a modified UHMWPE sheet was [...] Read more.

Modified ultra-high-molecular-weight polyethylene (UHMWPE) with calcium stearate (CS) and polyethylene wax (PEW) is a feasible method to improve the fluidity of materials because of the tense entanglement network formed by the extremely long molecular chains of UHMWPE, and a modified UHMWPE sheet was fabricated by compression molding technology. A Fourier-transform infrared spectroscopy test found that a new chemical bond was generated at 1097 cm⁻¹ in the materials. Besides, further tests on the thermal, thermomechanical, mechanical, and shape memory properties of the samples were also conducted, which indicates that all properties are affected by the dimension and distribution of crystal regions. Moreover, the experimental results indicate that the addition of PEW and CS can effectively improve the mechanical properties. Additionally, the best comprehensive performance of the samples was obtained at the PEW content of 5 wt % and the CS content of 1 wt %. In addition, the effect of temperature on the shape memory properties of the samples was investigated, and the results indicate that the shape fixity ratio (R_f) and the shape recovery ratio (R_r) can reach 100% at 115 °C and 79% at 100 °C, respectively, which can contribute to the development of UHMWPE-based shape memory polymers. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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24 pages, 12541 KiB

Open AccessArticle

Mechanical Characterization of the Plastic Material GF-PA6 Manufactured Using FDM Technology for a Compression Uniaxial Stress Field via an Experimental and Numerical Analysis

by Jorge Manuel Mercado-Colmenero, Cristina Martin-Doñate, Vincenzo Moramarco, Michele Angelo Attolico, Gilda Renna, Moises Rodriguez-Santiago and Caterina Casavola

Polymers 2020, 12(1), 246; https://doi.org/10.3390/polym12010246 - 20 Jan 2020

Cited by 24 | Viewed by 5921

Abstract

This manuscript presents an experimental and numerical analysis of the mechanical structural behavior of Nylstrong GF-PA6, a plastic material manufactured using FDM (fused deposition modeling) technology for a compression uniaxial stress field. Firstly, an experimental test using several test specimens fabricated in the [...] Read more.

This manuscript presents an experimental and numerical analysis of the mechanical structural behavior of Nylstrong GF-PA6, a plastic material manufactured using FDM (fused deposition modeling) technology for a compression uniaxial stress field. Firstly, an experimental test using several test specimens fabricated in the Z and X-axis allows characterizing the elastic behavior of the reinforced GF-PA6 according to the ISO 604 standard for uniaxial compression stress environments in both Z and X manufacturing orientations. In a second stage, an experimental test analyzes the structural behavior of an industrial part manufactured under the same conditions as the test specimens. The experimental results for the test specimens manufactured in the Z and X-axis present differences in the stress-strain curve. Z-axis printed elements present a purely linear elastic behavior and lower structural integrity, while X-axis printed elements present a nonlinear elastic behavior typical of plastic and foam materials. In order to validate the experimental results, numerical analysis for an industrial part is carried out, defining the material GF-PA6 as elastic and isotropic with constant Young’s compression modulus according to ISO standard 604. Simulations and experimental tests show good accuracy, obtaining errors of 0.91% on the Z axis and 0.56% on the X-axis between virtual and physical models. Full article

(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)

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