Polymers

Research

Jump to: Review

8 pages, 1597 KiB

Open AccessCommunication

Exploring Aromatic S-Thioformates as Photoinitiators

by Paul Rieger, Sabrina Pueschmann, Michael Haas, Max Schmallegger, Gema Guedes de la Cruz and Thomas Griesser

Polymers 2023, 15(7), 1647; https://doi.org/10.3390/polym15071647 - 26 Mar 2023

Viewed by 1190

Abstract

Thiyl radicals were generated from aromatic S-thioformates by photolysis. The corresponding photo-initiated decarbonylation allows initiating polymerization reactions in both acrylate- and thiol-acrylate-based resin systems. Compared to aromatic thiols, the introduction of the photolabile formyl group prevents undesired reactions with acrylate monomers allowing [...] Read more.

Thiyl radicals were generated from aromatic S-thioformates by photolysis. The corresponding photo-initiated decarbonylation allows initiating polymerization reactions in both acrylate- and thiol-acrylate-based resin systems. Compared to aromatic thiols, the introduction of the photolabile formyl group prevents undesired reactions with acrylate monomers allowing photoinitiators (PIs) with constant reactivity over storage. To demonstrate the potential of S-thioformates as PIs, the bifunctional molecule S,S′-(thiobis(4,1-phenylene))dimethanethioate (2b) was synthesized, providing reactivity under visible light excitation. Consequently, acrylate-based formulations could successfully be processed by digital light processing (DLP)-based stereolithography at 405 nm in high resolution. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Graphical abstract

13 pages, 4151 KiB

Open AccessArticle

Low Dielectric Constant Photocurable Fluorinated Poly (Phthalazinone Ether) Ink with Excellent Mechanical Properties and Heat Resistance

by Guangsheng Zhang, Chenghao Wang, Lingmei Jiang, Yibo Wang, Bing Wang, Xiaoxu Wang, Haoran Liu, Lishuai Zong, Jinyan Wang and Xigao Jian

Polymers 2023, 15(6), 1531; https://doi.org/10.3390/polym15061531 - 20 Mar 2023

Cited by 2 | Viewed by 1606

Abstract

The photosensitive resins for 3D printing technology have been widely applied throughout the advanced communication field due to their merits of high molding accuracy and fast processing speed. Regardless, they, in particular, should have better mechanical properties, heat resistance, and dielectric properties. Herein, [...] Read more.

The photosensitive resins for 3D printing technology have been widely applied throughout the advanced communication field due to their merits of high molding accuracy and fast processing speed. Regardless, they, in particular, should have better mechanical properties, heat resistance, and dielectric properties. Herein, photocurable fluorinated poly (phthalazinone ether) (FSt-FPPE) was utilized as a prepolymer to improve the performance of photosensitive resin. A series of UV-curable inks named FST/DPGs were prepared with FSt-FPPE and acrylic diluents of different mass fractions. The FST/DPGs were cured into films by UV curing and post-treatment. After curing, their properties were characterized in detail. In terms of heat resistance, glass transition temperature (T_g) could reach 233 °C and the 5% thermal decomposition temperature (T_d5%) was 371 °C. The tensile strength surprisingly reached 61.5 MPa, and the dielectric constant (D_k) could be significantly reduced to 2.75. Additionally, FST/DPGs were successfully employed in UV-assisted direct writing (DIW) to print 3D objects that benefited from their commendable fluidity and rapid curing speed. A stiff cylinder sample with a smooth surface and distinct pattern was ultimately obtained, indicating their remarkable 3D printing adaptation. Such photosensitive resin for UV-assisted DIW exhibits tremendous potential in the electronic industry. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Figure 1

19 pages, 5396 KiB

Open AccessArticle

Impact Performance of 3D Printed Spatially Varying Elastomeric Lattices

by Charles M. Dwyer, Jose G. Carrillo, Jose Angel Diosdado De la Peña, Carolyn Carradero Santiago, Eric MacDonald, Jerry Rhinehart, Reed M. Williams, Mark Burhop, Bharat Yelamanchi and Pedro Cortes

Polymers 2023, 15(5), 1178; https://doi.org/10.3390/polym15051178 - 26 Feb 2023

Cited by 5 | Viewed by 2430

Abstract

Additive manufacturing is catalyzing a new class of volumetrically varying lattice structures in which the dynamic mechanical response can be tailored for a specific application. Simultaneously, a diversity of materials is now available as feedstock including elastomers, which provide high viscoelasticity and increased [...] Read more.

Additive manufacturing is catalyzing a new class of volumetrically varying lattice structures in which the dynamic mechanical response can be tailored for a specific application. Simultaneously, a diversity of materials is now available as feedstock including elastomers, which provide high viscoelasticity and increased durability. The combined benefits of complex lattices coupled with elastomers is particularly appealing for anatomy-specific wearable applications such as in athletic or safety equipment. In this study, Siemens’ DARPA TRADES-funded design and geometry-generation software, Mithril, was leveraged to design vertically-graded and uniform lattices, the configurations of which offer varying degrees of stiffness. The designed lattices were fabricated in two elastomers using different additive manufacturing processes: (a) vat photopolymerization (with compliant SIL30 elastomer from Carbon) and (b) thermoplastic material extrusion (with Ultimaker™ TPU filament providing increased stiffness). Both materials provided unique benefits with the SIL30 material offering compliance suitable for lower energy impacts and the Ultimaker™ TPU offering improved protection against higher impact energies. Moreover, a hybrid lattice combination of both materials was evaluated and demonstrated the simultaneous benefits of each, with good performance across a wider range of impact energies. This study explores the design, material, and process space for manufacturing a new class of comfortable, energy-absorbing protective equipment to protect athletes, consumers, soldiers, first responders, and packaged goods. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Figure 1

20 pages, 13508 KiB

Open AccessArticle

Fused Deposition Modeling and Characterization of Heat Shape Memory Poly(lactic) Acid-Based Porous Vascular Scaffold

by Li Zhang, Muhammad Hanif, Jiacheng Li, Abdul Hakim Shah, Wajid Hussain and Guotao Zhang

Polymers 2023, 15(2), 390; https://doi.org/10.3390/polym15020390 - 11 Jan 2023

Cited by 4 | Viewed by 1624

Abstract

Shape memory polymers have received widespread attention from researchers because of their low density, shape variety, responsiveness to the environment, and transparency. This study deals with heat-shape memory polymers (SMPs) based on polylactic acid (PLA) for designing and fabricating a novel porous vascular [...] Read more.

Shape memory polymers have received widespread attention from researchers because of their low density, shape variety, responsiveness to the environment, and transparency. This study deals with heat-shape memory polymers (SMPs) based on polylactic acid (PLA) for designing and fabricating a novel porous vascular scaffold to treat vascular restenosis. The solid isotropic material penalization method (SIMP) was applied to optimize the vascular scaffolds. Based on the torsional torque loading of Hyperworks Optistruct and the boundary conditions, the topological optimization model of a vascular scaffold unit was established. Forward and reverse hybrid modeling technology was applied to complete the final stent structure’s assembly. The glass transition temperature for the present SMPs is 42.15 °C. With the increase in temperature, the ultimate tensile strength of the SMPs is reduced from 29.5 MPa to 11.6 MPa. The maximum modulus at room temperature was around 34 MPa. Stress relaxation curves show that the material classification is a “thermoset” polymer. The superb mechanical properties, the transition temperature of the SMPs, and the recovery ratio made it a feasible candidate for a vascular scaffold. A circular tube based on the shape memory polymers was presented as an example for analyzing the recovery ratio in an unfolding state. A higher recovery ratio was obtained at a temperature of 65 °C with a tube thickness of 2 mm. Finally, the proposed porous vascular scaffold was successfully fabricated, assessed, and compared with the original and previously developed vascular scaffolds. The proposed scaffold structure regains its initial shape with a recovery ratio of 98% (recovery temperature of 47 °C) in 16 s. The tensile strength, Young’s modulus, and bending strength of the proposed scaffold were 29.5 MPa, 695.4 MPa, and 6.02 MPa, respectively. The results showed that the proposed scaffold could be regarded as a potential candidate for a vascular implantation. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Figure 1

17 pages, 5158 KiB

Open AccessArticle

Ethylene-Vinyl Acetate Copolymers as Potential Thermoplastic Modifiers of Photopolymer Compositions

by Dmitriy A. Bazhanov, Arkadiy A. Poteryaev, Alexey V. Shapagin and Anna A. Shcherbina

Polymers 2023, 15(1), 131; https://doi.org/10.3390/polym15010131 - 28 Dec 2022

Cited by 3 | Viewed by 1598

Abstract

The possibility of using thermoplastic polymers in photopolymer compositions for SLA and DLP is discussed in this article. The diffusion and mutual solubility of uncured systems based on tert-butyl acrylate (tBA) and ethylene-vinyl acetate copolymers (EVA) or low-density polyethylene (LDPE) were studied. The [...] Read more.

The possibility of using thermoplastic polymers in photopolymer compositions for SLA and DLP is discussed in this article. The diffusion and mutual solubility of uncured systems based on tert-butyl acrylate (tBA) and ethylene-vinyl acetate copolymers (EVA) or low-density polyethylene (LDPE) were studied. The solubility and diffusion of tBA with EVA containing 7, 20, and 40 wt.% vinyl acetate (VA) and with LDPE in the temperature range 20–75 °C were studied by optical micro-interferometry method. Phase diagrams of LDPE–tBA, EVA-7–tBA, and EVA-20–tBA systems were obtained. It is shown that the compositions are characterized by the phase-state diagrams of amorphous separation with the upper critical solution temperature (UCST). The concentration dependences of the interdiffusion coefficients as well as dependences of the self-diffusion coefficients on VA content and on temperature were plotted. The activation energy of self-diffusion of EVA and LDPE was calculated. It was shown that the most promising tBA modifier is EVA-40, which is completely soluble at all studied temperature ranges. The obtained data on the mixing of the initial components is valuable for further studies of the processes of structure formation during photocuring of compositions, regulation of the phase structure and, as a consequence, the performance characteristics of the 3D printable materials. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Figure 1

14 pages, 2585 KiB

Open AccessArticle

Vat Photopolymerization 3D-Printing of Dynamic Thiol-Acrylate Photopolymers Using Bio-Derived Building Blocks

by Usman Shaukat, Bernhard Sölle, Elisabeth Rossegger, Sravendra Rana and Sandra Schlögl

Polymers 2022, 14(24), 5377; https://doi.org/10.3390/polym14245377 - 8 Dec 2022

Cited by 12 | Viewed by 2147

Abstract

As an energy-efficient additive manufacturing process, vat photopolymerization 3D-printing has become a convenient technology to fabricate functional devices with high resolution and freedom in design. However, due to their permanently crosslinked network structure, photopolymers are not easily reprocessed or repaired. To improve the [...] Read more.

As an energy-efficient additive manufacturing process, vat photopolymerization 3D-printing has become a convenient technology to fabricate functional devices with high resolution and freedom in design. However, due to their permanently crosslinked network structure, photopolymers are not easily reprocessed or repaired. To improve the environmental footprint of 3D-printed objects, herein, we combine the dynamic nature of hydroxyl ester links, undergoing a catalyzed transesterification at elevated temperature, with an acrylate monomer derived from renewable resources. As a sustainable building block, we synthesized an acrylated linseed oil and mixed it with selected thiol crosslinkers. By careful selection of the transesterification catalyst, we obtained dynamic thiol-acrylate resins with a high cure rate and decent storage stability, which enabled the digital light processing (DLP) 3D-printing of objects with a structure size of 550 µm. Owing to their dynamic covalent bonds, the thiol-acrylate networks were able to relax 63% of their initial stress within 22 min at 180 °C and showed enhanced toughness after thermal annealing. We exploited the thermo-activated reflow of the dynamic networks to heal and re-shape the 3D-printed objects. The dynamic thiol-acrylate photopolymers also demonstrated promising healing, shape memory, and re-shaping properties, thus offering great potential for various industrial fields such as soft robotics and electronics. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Graphical abstract

13 pages, 2407 KiB

Open AccessArticle

Photocurable 3D-Printable Systems with Controlled Porosity towards CO₂ Air Filtering Applications

by Annalisa Chiappone, Alessandro Pedico, Stefania Porcu, Candido Fabrizio Pirri, Andrea Lamberti and Ignazio Roppolo

Polymers 2022, 14(23), 5265; https://doi.org/10.3390/polym14235265 - 2 Dec 2022

Cited by 2 | Viewed by 1345

Abstract

Porous organic polymers are versatile platforms, easily adaptable to a wide range of applications, from air filtering to energy devices. Their fabrication via vat photopolymerization enables them to control the geometry on a multiscale level, obtaining hierarchical porosity with enhanced surface-to-volume ratio. In [...] Read more.

Porous organic polymers are versatile platforms, easily adaptable to a wide range of applications, from air filtering to energy devices. Their fabrication via vat photopolymerization enables them to control the geometry on a multiscale level, obtaining hierarchical porosity with enhanced surface-to-volume ratio. In this work, a photocurable ink based on 1,6 Hexanediol diacrylate and containing a high internal phase emulsion (HIPE) is presented, employing PLURONIC F-127 as a surfactant to generate stable micelles. Different parameters were studied to assess the effects on the morphology of the pores, the printability and the mechanical properties. The tests performed demonstrates that only water-in-oil emulsions were suitable for 3D printing. Afterwards, 3D complex porous objects were printed with a Digital Light Processing (DLP) system. Structures with large, interconnected, homogeneous porosity were fabricated with high printing precision (300 µm) and shape fidelity, due to the addition of a Radical Scavenger and a UV Absorber that improved the 3D printing process. The formulations were then used to build scaffolds with complex architecture to test its application as a filter for CO₂ absorption and trapping from environmental air. This was obtained by surface decoration with NaOH nanoparticles. Depending on the surface coverage, tested specimens demonstrated long-lasting absorption efficiency. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Figure 1

Review

Jump to: Research

30 pages, 6892 KiB

Open AccessReview

Advanced Formulations Based on Poly(ionic liquid) Materials for Additive Manufacturing

by Sara Miralles-Comins, Marcileia Zanatta and Victor Sans

Polymers 2022, 14(23), 5121; https://doi.org/10.3390/polym14235121 - 24 Nov 2022

Cited by 9 | Viewed by 2976

Abstract

Innovation in materials specially formulated for additive manufacturing is of great interest and can generate new opportunities for designing cost-effective smart materials for next-generation devices and engineering applications. Nevertheless, advanced molecular and nanostructured systems are frequently not possible to integrate into 3D printable [...] Read more.

Innovation in materials specially formulated for additive manufacturing is of great interest and can generate new opportunities for designing cost-effective smart materials for next-generation devices and engineering applications. Nevertheless, advanced molecular and nanostructured systems are frequently not possible to integrate into 3D printable materials, thus limiting their technological transferability. In some cases, this challenge can be overcome using polymeric macromolecules of ionic nature, such as polymeric ionic liquids (PILs). Due to their tuneability, wide variety in molecular composition, and macromolecular architecture, they show a remarkable ability to stabilize molecular and nanostructured materials. The technology resulting from 3D-printable PIL-based formulations represents an untapped array of potential applications, including optoelectronic, antimicrobial, catalysis, photoactive, conductive, and redox applications. Full article

(This article belongs to the Special Issue Advanced Materials in 3D Printing Technology)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Advanced Materials in 3D Printing Technology

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI