Re-entrant solid behavior of 3D-printable epoxy inks

Ekbote, Rishabh P.; Donley, Gavin J.; Liu, Deborah Y.; Rogers, Simon A.; Krogstad, Daniel V.

doi:10.1007/s00397-020-01227-3

Cited by 3 publications

(6 citation statements)

References 41 publications

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“…Our previous work showed that EMIM-DCA can induce selfassembly of P-123 in epoxy blends. 27 EMIM-DCA IL plays a critical role in driving self-assembly of P-123 BCPs, which is seen when this result is compared with existing results reported for other epoxy/PEO−PPO−PEO blends. To further explore the interactions between epoxy, P-123, and EMIM-DCA, uncured ternary blends were characterized using SAXS to identify the morphology of the self-assembled structures.…”

Section: ■ Results and Discussionsupporting

confidence: 77%

“…25 Additionally, we recently showed that the use of an ionic liquid (IL) curing agent (1ethyl-3-methylimidazolium dicyanamide (EMIM-DCA)) could result in the self-assembly of PEO−PPO−PEO in an epoxy resin at room temperature. 27 The use of ILs as curing agents in epoxy resins has attracted interest, as ILs have a number of potential benefits over traditional curing agents. These include latent curing ability, higher epoxy conversion, flame retardancy, and enhanced conductivity.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Cano et al showed that the change of the curing agent from 4,4′-methylenedianiline to m -xylylenediamine resulted in a system with a lower critical solution temperature (LCST), in which the BCPs self-assembled at temperatures above the LCST, and formed nanostructures through RIMPS at temperatures below the LCST . Additionally, we recently showed that the use of an ionic liquid (IL) curing agent (1-ethyl-3-methylimidazolium dicyanamide (EMIM-DCA)) could result in the self-assembly of PEO–PPO–PEO in an epoxy resin at room temperature …”

Section: Introductionmentioning

confidence: 99%

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Self-Assembly and Phase Transformation of Block Copolymer Nanostructures in Ionic Liquid-Cured Epoxy

Liu

Krogstad

2021

Macromolecules

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Epoxy/block copolymer (BCP) blends are highly versatile materials. The BCPs can form nanostructures in the resins that improve the toughness of the thermoset as well as provide a template for nanoparticles. However, to fully unlock their potential, more needs to be understood about how to form and stabilize long-range ordered nanostructures within the unique chemical environment of a cured epoxy matrix. In this work, an ionic liquid (1-ethyl-3-methylimidazolium dicyanamide) was used as both the curing agent and a structure-directing agent in an epoxy/poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) blend. Small-angle X-ray scattering (SAXS) analysis of the ternary phase space of the epoxy/BCP/ionic liquid blend showed that a wide range of self-assembled structures were attained in the uncured blends using this low-cost BCP, including higher ordered structures such as hexagonally packed cylinders and lamellar structures. Comparisons of the structures before and after epoxy curing showed that many of the compositions undergo phase transitions during the curing process. In situ SAXS showed that these transitions can be quite complex for some compositions. Importantly, it was shown that these phase changes proceed through a variety of transition structures rather than dissolving and reforming the new structures. These findings demonstrate new strategies for imparting long-range order in epoxy/BCP blends through the use of ionic liquid curing agents.

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Section: ■ Results and Discussionsupporting

confidence: 77%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Self-Assembly and Phase Transformation of Block Copolymer Nanostructures in Ionic Liquid-Cured Epoxy

Liu

Krogstad

2021

Macromolecules

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“…PreEs with lower M c are produced. The solid state of preE or a solid-like character is also important for the application of 3D-printable epoxy inks [ 24 ].…”

Section: Resultsmentioning

confidence: 99%

New Insights on Expandability of Pre-Cured Epoxy Using a Solid-State CO2-Foaming Technique

et al. 2021

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Foaming an epoxy is challenging because the process involves the curing reaction of epoxy and hardener (from monomer to oligomer, to a gel and a final three-dimensional crosslinked network) and the loading of gas phase into the epoxy phase to develop the cellular structure. The latter process needs to be carried out at the optimum curing stage of epoxy to avoid cell coalescence and to allow expansion. The environmental concern regarding the usage of chemical blowing agent also limits the development of epoxy foams. To surmount these challenges, this study proposes a solid-state CO2 foaming of epoxy. Firstly, the resin mixture of diglycidylether of bisphenol-A (DGEBA) epoxy and polyamide hardener is pre-cured to achieve various solid-state sheets (preEs) of specific storage moduli. Secondly, these preEs undergo CO2 absorption using an autoclave. Thirdly, CO2 absorbed preEs are allowed to free-foam/expand in a conventional oven at various temperatures; lastly, the epoxy foams are post-cured. PreE has a distinctive behavior once being heated; the storage modulus is reduced and then increases due to further curing. Epoxy foams in a broad range of densities could be fabricated. PreE with a storage modulus of 4 × 104–1.5 × 105 Pa at 30 °C could be foamed to densities of 0.32–0.45 g/cm3. The cell morphologies were revealed to be star polygon shaped, spherical and irregularly shaped. The research proved that the solid-state CO2-foaming technique can be used to fabricate epoxy foams with controlled density.

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“…That technology offers a whole new range of polymeric materials in which additive manufacturing can be carried out. Employing this technique, materials like epoxy resins [ 9 , 10 ], preceramic polymers [ 7 , 11 , 12 , 13 , 14 ], natural polymers [ 3 , 15 , 16 ], or conductive composite polymers [ 17 , 18 , 19 , 20 , 21 ] can be tailored as convenience for biomedical applications. Furthermore, it is the preferred technique for printing living cells by mixing them in hydrogels due to the high survival rate [ 22 , 23 , 24 , 25 , 26 ], in addition to the biocompatible water-rich environment that simulates the extracellular matrix (ECM) [ 27 ].…”

Section: Introductionmentioning

confidence: 99%

Continuous Based Direct Ink Write for Tubular Cardiovascular Medical Devices

2020

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Bioresorbable cardiovascular applications are increasing in demand as fixed medical devices cause episodes of late restenosis. The autologous treatment is, so far, the gold standard for vascular grafts due to the similarities to the replaced tissue. Thus, the possibility of customizing each application to its end user is ideal for treating pathologies within a dynamic system that receives constant stimuli, such as the cardiovascular system. Direct Ink Writing (DIW) is increasingly utilized for biomedical purposes because it can create composite bioinks by combining polymers and materials from other domains to create DIW-printable materials that provide characteristics of interest, such as anticoagulation, mechanical resistance, or radiopacity. In addition, bioinks can be tailored to encounter the optimal rheological properties for the DIW purpose. This review delves into a novel emerging field of cardiovascular medical applications, where this technology is applied in the tubular 3D printing approach. Cardiovascular stents and vascular grafts manufactured with this new technology are reviewed. The advantages and limitations of blending inks with cells, composite materials, or drugs are highlighted. Furthermore, the printing parameters and the different possibilities of designing these medical applications have been explored.

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Re-entrant solid behavior of 3D-printable epoxy inks

Cited by 3 publications

References 41 publications

Self-Assembly and Phase Transformation of Block Copolymer Nanostructures in Ionic Liquid-Cured Epoxy

Self-Assembly and Phase Transformation of Block Copolymer Nanostructures in Ionic Liquid-Cured Epoxy

New Insights on Expandability of Pre-Cured Epoxy Using a Solid-State CO2-Foaming Technique

Continuous Based Direct Ink Write for Tubular Cardiovascular Medical Devices

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