Effect of a Heterogeneous Network on the Fracture Behavior of Epoxy Resins

Shundo, Atsuomi; Aoki, Mizuho; Wang, Pangpang; Hoshino, Taiki; Yamamoto, Satoru; Yamada, Sunao; Tanaka, Keiji

doi:10.1021/acs.macromol.3c00341

Cited by 20 publications

(12 citation statements)

References 44 publications

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“…Figure shows WAXS profiles for 4,4′-DGEBA and 4,4′-DGEBF at 353 K. 4,4′-DGEBA exhibited a broad peak centered at a scattering vector ( q ) of approximately at 13 nm –1 , corresponding to the domain spacing ( d- spacing) of 0.5 nm. In WAXS, the scattering contrast arises from differences in the electron density . Since the electron density of phenyl rings is relatively higher than that of other moieties, the d -spacing reflects the distance between phenyl rings .…”

Section: Resultsmentioning

confidence: 99%

Exploring the Impact of Molecular Structure on Curing Kinetics: A Comparative Study of Diglycidyl Ether of Bisphenol A and F Epoxy Resins

Shundo,

Thao Phan,

Aoki

et al. 2024

J. Phys. Chem. B

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Epoxy resins are essential for various applications, and their properties depend on the curing reactions during which epoxy and amine compounds form the network structure. We here focus on how the presence or absence of two methyl groups in common epoxy bases, diglycidyl ether of bisphenol A and F (4,4′-DGEBA and 4,4′-DGEBF), affects the curing kinetics. The chemical reactions of both 4,4′-DGEBA and 4,4′-DGEBF, when cured with the same amine, were monitored by Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Despite no difference in the reactivity of epoxy groups between 4,4′-DGEBA and 4,4′-DGEBF, the initial curing reaction was slower for the latter. This delay for the 4,4′-DGEBF system was attributed to intermolecular stacking, which hindered the approach of unreacted epoxy groups to amino groups and vice versa. This conclusion was drawn from the results obtained through ultraviolet (UV) spectroscopy, wide-angle X-ray scattering (WAXS), density functional theory (DFT) calculation, and all-atom molecular dynamics (MD) simulation.

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Section: Resultsmentioning

confidence: 99%

Exploring the Impact of Molecular Structure on Curing Kinetics: A Comparative Study of Diglycidyl Ether of Bisphenol A and F Epoxy Resins

Shundo,

Thao Phan,

Aoki

et al. 2024

J. Phys. Chem. B

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“…The adhesive technology used for assembling two dissimilar materials is widely adopted in various industries, including automotive, aerospace, construction, electronics, and healthcare. − One of the most common thermosetting adhesives is a class of epoxy resins, composed of an epoxy base and a hardener such as amine groups. − The resin solidifies on an adherend through curing reactions, forming an interface with the adherend. Mechanical properties of the resin are closely related to the resultant network structure formed by the curing reactions in the bulk − as well as at the interface. − As some interfacial events dominate the adhesion phenomena, it is crucial to better understand what kinds of interactions at the interface contribute to the adhesive strength from both theoretical and experimental perspectives.…”

Section: Introductionmentioning

confidence: 99%

Electronic Interaction of Epoxy Resin with Copper at the Adhered Interface

Saeki,

Kawaguchi,

Tsuji

et al. 2024

Langmuir

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A better understanding of the aggregation states of adhesive molecules in the interfacial region with an adherend is crucial for controlling the adhesion strength and is of great inherent academic interest. The adhesion mechanism has been described through four theories: adsorption, mechanical, diffusion, and electronic. While interfacial characterization techniques have been developed to validate the aforementioned theories, that related to the electronic theory has not yet been thoroughly studied. We here directly detected the electronic interaction between a commonly used thermosetting adhesive, cured epoxy of diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diaminodiphenylmethane (DDM), and copper (Cu). This study used a combination of density functional theory (DFT) calculations and femtosecond transient absorption spectroscopic (TAS) measurements as this epoxy adhesive-Cu pairing is extensively used in electronic device packaging. The DFT calculations predicted that π electrons in a DDM molecule adsorbed onto the Cu surface flowed out onto the Cu surface, resulting in a positive charge on the DDM. TAS measurements for the Cu/epoxy multilayer film, a model sample containing many metal/adhesive interfaces, revealed that the electronic states of excited DDM moieties at the Cu interface were different from those in the bulk region. These results were in good accordance with the prediction by DFT calculations. Thus, it can be concluded that TAS is applicable to characterize the electronic interaction of adhesives with metal adherends in a nondestructive manner.

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“…In bending deformation, local structure analysis is required because the strain is positive in the convex part and negative in the concave part from a neutral plane where the strain is zero. Consequently, microbeam X-ray scattering in synchrotron radiation facilities which is effective for local structural analysis − is used in this study. Furthermore, since large structure changes such as the formation of voids and crazes are expected, ultrasmall-angle X-ray scattering (USAXS) was also performed.…”

Section: Introductionmentioning

confidence: 99%

X-ray Scattering Analyses on an Aggregation Structure of Poly(ethylene terephthalate) Films under Bending Deformation

Ohara,

Kojio

2024

Macromolecules

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With the recent development of foldable electronic devices, there is a growing demand for display materials that exhibit resistance to the formation of fold marks (folding resistance). While polyethylene terephthalate (PET) films biaxially stretched in machine direction (MD) and transverse direction (TD) are commonly used as display films, they have poor folding resistance, especially when folded in the strongly stretched direction. Therefore, we aim to elucidate the primary factors behind fold mark formation in PET films, focusing on the anisotropy of the folding resistance. To analyze the aggregation structure changes resulting from bending deformation, synchrotron X-ray scattering measurements (ultrasmall, small, and wide-angle X-ray scattering; USAXS, SAXS, and WAXS) were performed. The PET films strongly stretched in the TD direction were kept folded in either MD or TD direction, and X-rays were irradiated in the surface normal or edge direction of the film to analyze their structure changes from various angles. As a result, in the convex region, the normal direction of the lamella coincided with the direction of the principal stress, whereas in the concave region, it was inclined at a 40−45°angle to the principal stress. On the other hand, the (100) plane of the crystal lattice maintained its orientation parallel to the film surface from convex to concave, although the orientation was slightly disrupted in the concave region. These results suggest that polymer chains slip parallel to the chain direction, causing no change in the orientation of the polymer chains but only the normal of the lamellar surface. When the PET films were folded in the TD direction, which shows poor folding resistance, the formation of a tilted lamellar surface was more pronounced compared to MD folding. Given that the formation of transformed lamellae caused by the chain slip is related to plastic deformation, which leads to permanent strain, this deformation contributes to the formation of fold marks. As the molecular chains are oriented in the strongly stretched direction, TD direction, it is assumed that they are more susceptible to forming kinks and yielding when subjected to compressive deformation within the concave region.

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Effect of a Heterogeneous Network on the Fracture Behavior of Epoxy Resins

Cited by 20 publications

References 44 publications

Exploring the Impact of Molecular Structure on Curing Kinetics: A Comparative Study of Diglycidyl Ether of Bisphenol A and F Epoxy Resins

Exploring the Impact of Molecular Structure on Curing Kinetics: A Comparative Study of Diglycidyl Ether of Bisphenol A and F Epoxy Resins

Electronic Interaction of Epoxy Resin with Copper at the Adhered Interface

X-ray Scattering Analyses on an Aggregation Structure of Poly(ethylene terephthalate) Films under Bending Deformation

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