On the Nature of Epoxy Resin Post-Curing

Moller, James C.; Berry, Rajiv; Foster, Heather A.

doi:10.3390/polym12020466

Cited by 38 publications

(21 citation statements)

References 62 publications

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“…Thermal post-curing is used as an effective and simple method for improving the mechanical properties, increasing T g and dehydrating the samples. [44] Due to an increase in the mobility of polymer chains and radicals, which are unreactive at room temperature due to steric hindrances, additional polymerization of the sample occurs under the thermal post-curing conditions. Since thermal post-curing does not depend on diffusion of the photoinitiator inside the sample, the method is not sensitive to the geometry of the product.…”

Section: Introductionmentioning

confidence: 99%

4D Printing of Shape‐Memory Semi‐Interpenetrating Polymer Networks Based On Aromatic Heterochain Polymers

Bardakova

Kholkhoev

Farion

et al. 2021

Adv Materials Technologies

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advent of smart materials. These materials are called smart due to their self-sensing, self-adaptability, memory capabilities and manifold functions. [1,2] Smart materials are capable of transforming their physical properties (dimensions, shape, stiffness, viscosity, adhesion, and color) following the action of different stimuli, namely, temperature, mechanical strength, electric current, light, magnetic field, chemicals, etc. [3][4][5] A combination of smart materials and 3D printing has resulted in a new field known as 4D printing. 4D printed articles may be used in different fields, including electronics, [2] aerospace industry, [1,2] engineering, [6] sensorics, [2] robotics and medicine. [7] Thermosensitive shape-memory polymers (SMPs) are the most widely studied and used group of materials. [8] In the structure of heat-sensitive SMPs, stiff segments are responsible for the retention of the permanent shape, while flexible segments are responsible for the fixation and retention of the temporary form. [8] Compared with inorganic ceramics and metallic smart materials, SMPs possess such advantages as simpler processing, chemical stability, high stress tolerance, and high recoverable strains. [4] A significant problem of the wide use of both 4D printing and 3D printing in general is a limited range of polymeric Mostof the presently known thermosensitive shape-memory polymers suitable for 4D printing have insufficient mechanical strength and thermal stability that restricts their potential areas of application. Here, new photosensitive compositions (PSCs) based on aromatic heterochain polymers -poly-N,N′-(m-phenylene)isophthalamide (MPA) or poly-2,2′-(p-oxydiphenylene)-5,5′dibenzimidazole (OPBI) -for DLP printing are proposed. Thermal post-curing and supercritical carbon dioxide (scCO 2 ) are used for post-processing of the structures. During the scCO 2 treatment the removal of unreacted monomeric component (N,N-dimethylacrylamide) and its uncrosslinked oligomers is accompanied by the preservation of the initial degree of crosslinking. The more stable shrinkage is observed for the combined post-processing method (T°+scCO 2 ) in the case of OPBI-PSC and after the heat treatment for MPA-PSC specimens. The method of post-processing and the nature of the heterochain polymer strongly affect the mechanical properties and thermal resistance of the structures. The tensile strength has the maximum value after the thermal posttreatment (101.1 ± 7.1 and 78.4 ± 5.1 MPa of OPBI-PSC and MPA-PSC, respectively). The intense destruction of the materials is observed at 393 and 408 °C for MPA-PSC and OPBI-PSC, respectively. Moreover, the 4D-printed structures exhibit excellent shape memory performance at transition temperatures >100 °C, thus have a great potential for the use in aerospace, robotics, sensorics.

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Section: Introductionmentioning

confidence: 99%

4D Printing of Shape‐Memory Semi‐Interpenetrating Polymer Networks Based On Aromatic Heterochain Polymers

Bardakova

Kholkhoev

Farion

et al. 2021

Adv Materials Technologies

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show abstract

“…The main parameters, i.e., the minimum cross-linking radius, maximum cross-linking radius, step-cross-linking radius, iterations per radius, target degree of cross-linking, and cross-linking temperature, are set as 4 Å, 12 Å, 1 Å, 3, 100%, and 500 K, respectively. A high simulation temperature is beneficial to the movement of molecular segments in the cross-linked system and can reduce the simulation time . The Andersen and Berendsen methods are used for temperature (thermostat) and pressure (barostat) controls, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…A high simulation temperature is beneficial to the movement of molecular segments in the cross-linked system and can reduce the simulation time. 23 The Andersen and Berendsen methods are used for temperature (thermostat) and pressure (barostat) controls, respectively. The crosslinking density is defined as the ratio of the number of newly formed C−N bonds to the theoretically formed C−N bonds.…”

Section: T H Imentioning

confidence: 99%

Directional Control of the Mechanical Properties of a Resin-Cross-Linking System: A Molecular Dynamics Study

Chen

et al. 2021

Ind. Eng. Chem. Res.

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Although thermosetting resins have good physical and chemical stabilities, their deformation ability is limited and fatigue fracture can easily occur. To overcome the defects of thermosetting resins, we propose introducing an aromatic heterocyclic helical macromolecule chain into a thermosetting resin-cross-linked network. The effect of the helical structure on the thermomechanical properties of the thermosetting resincured system is quantitatively and qualitatively analyzed using a molecular dynamics method. Results show that the helical structure can affect the mechanical properties of the thermosetting resin-cross-linked system along the pitch direction. The introduction of a helical macromolecule chain reduces the density of the cross-linking points and weakens the heat resistance of the cured system to some extent; however, the influence is insignificant. Nevertheless, we are expected to gain some deep insights into the directional control of the mechanical properties of the resin-curing system and microstructure of the cross-linking network by introducing a helical structure.

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“…In this study, the high-performance epoxy resin diglycidyl ether of bisphenol A (DGEBA) crosslinked with curing agent 4,4′diaminodiphenyl sulphone (44DDS) is selected as the representative because of its relative high properties and widely commercial applications (Mohan, 2013;Moller et al, 2020). The molecular structures of DGEBA and 44DDS and the details of the crosslinking process are shown in Figure 1.…”

Section: Atomistic Simulationsmentioning

confidence: 99%

Enhanced Interfacial Properties of Carbon Nanomaterial–Coated Glass Fiber–Reinforced Epoxy Composite: A Molecular Dynamics Study

et al. 2022

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The weak interfacial adhesion has significantly affected the durability, long-term reliability, and performance of glass fiber–reinforced epoxy composites. The coating of graphene and carbon nanotubes on the glass fiber can have a positive effect on the strength, toughness, and thermal insulation performance of glass fiber-reinforced composites. However, the strengthening mechanism of carbon nanomaterial coating on the interfacial adhesion between glass fiber and epoxy has not been fully explored. In this work, the effect of graphene and single-walled carbon nanotubes (SWCNTs) on the interfacial properties of the glass fiber–reinforced epoxy has been investigated at atomistic scale. The graphene and SWCNTs are sandwiched between epoxy and silica to study the debonding behavior of the sandwiched structures. It is found that the interfacial energy is significantly improved with the incorporation of graphene and SWCNTs between epoxy and silica, causing an obvious improvement in adhesion stress for graphene coating and in debonding displacement for SWCNT coating. Compared with the epoxy/silica without coatings where the silica and epoxy detach from the contact surface, the sandwiched structures display different failure modes. The sandwiched structure with graphene coating fails at the epoxy matrix close to the interface, exhibiting a cohesive failure mode because of the relatively stronger interfacial interactions. The structures with SWCNTs fail at the interface between silica and SWCNTs, representing an adhesive failure mode due to the interlocking between SWCNTs and polymer chains. This work provides a theoretical guideline to optimize the interface adhesion of coated glass fiber–reinforced epoxy via structure design and surface modification of coating materials.

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On the Nature of Epoxy Resin Post-Curing

Cited by 38 publications

References 62 publications

4D Printing of Shape‐Memory Semi‐Interpenetrating Polymer Networks Based On Aromatic Heterochain Polymers

4D Printing of Shape‐Memory Semi‐Interpenetrating Polymer Networks Based On Aromatic Heterochain Polymers

Directional Control of the Mechanical Properties of a Resin-Cross-Linking System: A Molecular Dynamics Study

Enhanced Interfacial Properties of Carbon Nanomaterial–Coated Glass Fiber–Reinforced Epoxy Composite: A Molecular Dynamics Study

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