Influence of the Epoxy/Acid Stoichiometry on the Cure Behavior and Mechanical Properties of Epoxy Vitrimers

Improving bonding and mechanical strengths is important for the application of bond coats used in the construction of steel deck bridges. Graphene nanoplatelets (GNPs) are attractive nanofillers for polymer modification because of their low cost, ultra-high aspect ratio, and extraordinary thermal and mechanical performance. In this paper, GNPs were used to reinforce the epoxy asphalt bond coat (EABC). The morphology, viscosity–time behavior, contact angle, dynamic mechanical properties, and mechanical and bonding strengths of GNP-reinforced EABCs were investigated using laser confocal microscopy, a Brookfield rotational viscometer, a contact angle meter, dynamic mechanical analysis, a universal test machine, and single-lap shear and pull-off adhesion tests. GNP dispersed non-uniformly in the asphalt phase of EABC. The viscosity of the neat EABC was lowered with the inclusion of GNPs and thus the allowable construction time was extended. The existence of GNPs enhances the hydrophobicity of the neat EABC. When adding more than 0.2% GNP, the storage modulus, crosslinking density and glass transition temperatures of both asphalt and epoxy of the neat EABC increased. The mechanical and bonding properties of the neat EABC were greatly enhanced with the incorporation of GNPs. Furthermore, the mechanical and bonding strengths of the modified EABCs increased with the GNP content. GNP-reinforced EABCs can be utilized in the pavement of long-span steel bridges with long durability.

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“…In a tensile test, the integral of the stress ( σ ) vs. strain ( ε ) curve indicates the toughness ( τ ) of the material [ 57 , 58 ]. Thus,

where ε b is the elongation at break.…”

Section: Resultsmentioning

confidence: 99%

Enhancement of Bonding and Mechanical Performance of Epoxy Asphalt Bond Coats with Graphene Nanoplatelets

et al. 2023

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“…The results show that the introduction of DA adducts can reduce the E a of the epoxy system. The role of hydroxyl groups on DA adducts in reaction with epoxy groups and reducing E a in epoxy curing has been previously investigated in the relevant literature. − At the same time, to confirm the stable existence of DA adducts in the epoxy resin system, molecular structure monitoring of EP-30% DA resin stock solution and the cured product was conducted by using FTIR at room temperature (Figure b). The characteristic peaks of bismaleimide in the spectra of EP-30% DA cured products were 690 cm –1 (C–H), 1708 cm –1 (CO), 1180 cm –1 (C–N–C, succinimide), and 1774 cm –1 (succinimide ring). , Among them, the maleimide peak at 1774 cm –1 is thought to be the result of participation in DA reactions, but its intensity is usually weak.…”

Section: Results and Discussionmentioning

confidence: 99%

Self-Healing and Flame-Retardant Modifications of Epoxy Resins by the Diels–Alder Release-Delivery Strategy for a High-Efficiency and Green Application

Lian

Zhang

et al. 2023

Ind. Eng. Chem. Res.

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The sustainability of epoxy thermosets (EPs) and EP-based composites is always limited by the evolution of internal microcracks and flammability. Herein, inspired by the drug release-delivery system for disease treatment, these symptoms of EP are solved efficiently by a multifunctional Diels–Alder (DA) release-delivery system. First, this novel system is fabricated by the cyclization reaction between the furan diene-containing phosphorus derivative and the maleimide dienophile. The resultant DA system is linked to the epoxy resin by the grafting reaction, thus ensuring its uniform dispersion. Being faced with the formation of inner microcracks, the maleimide dienophiles were released from the DA adducts under the mediated action of temperature and then were delivered to the targeted microcracks under the chemical potential difference derived from the variation of free volume. Then, the released maleimide molecules re-connect with the furan groups that existed near the microcracks to complete the repairing of the EP matrix. The skeletal structure of the EP was well preserved throughout the restoration process. Satisfactory flexural strength (105.5 MPa) and excellent crack-healing efficiency (104.5%) can be obtained for the modified EP. After three constant strain cycles, the stress retention rate can be readily maintained (more than 75%). In addition, due to the phosphorus–nitrogen synergistic flame-retardant effect from the DA system, not only the limited oxygen index of the DA-modified EP matrix can be improved to 27.5% but the lower peak release rate and lower total heat release are also observed compared with the unmodified EP.

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“…The loss modulus (E”) represents the energy dissipation ability of a material. For a polymer, E” is related to the morphology, glass transition, molecular motions, relaxation and so on [ 43 , 44 ]. As illustrated in Figure 8 , all E”–temperature curves show two peaks in the temperature range of −30–30 °C, indicating that all EABCs have two glass transitions: the glass transition of asphalt at the lower temperature and the glass transition of epoxy at the higher temperature.…”

Section: Resultsmentioning

confidence: 99%

Graphene Oxide-Modified Epoxy Asphalt Bond Coats with Enhanced Bonding Properties

et al. 2022

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The bonding strength of the bond coat plays an important role in the composite action between the wearing surface and the deck plate of the orthotropic steel deck system. Poor bonding results in the delamination of the wearing surface from the deck plate. Graphene oxide (GO) possesses outstanding mechanical and thermal properties, as well as impressive multifunctional groups, which makes it an ideal reinforcement candidate for polymer matrices. In this study, graphene oxide was used to improve the bonding strength and toughness of the epoxy asphalt bond coat (EABC). The dispersion, hydrophobicity, viscosity–time behavior, phase-separated morphology, dynamic mechanical properties, pull-off strength, shear strength and mechanical performance of GO-modified EABCs were investigated using various techniques. The inclusion of GO improved the hydrophobicity of the unmodified EABC. The viscosity of the unmodified EABC was lowered with the addition of GO during curing. Moreover, the allowable construction time for the modified EABCs was extended with the GO loading. The incorporation of GO enhanced the stiffness of the unmodified EABC in the glassy and rubbery states. However, graphene oxide lowered the glass transition temperature of the asphalt of the unmodified EABC. Confocal microscopy observations revealed that GO was invisible in both the asphalt and epoxy phases of the EABC. The inclusion of GO improved the bonding strength, particularly at 60 °C, and mechanical properties of the unmodified EABC.

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Influence of the Epoxy/Acid Stoichiometry on the Cure Behavior and Mechanical Properties of Epoxy Vitrimers

Cited by 19 publications

References 55 publications

Enhancement of Bonding and Mechanical Performance of Epoxy Asphalt Bond Coats with Graphene Nanoplatelets

Enhancement of Bonding and Mechanical Performance of Epoxy Asphalt Bond Coats with Graphene Nanoplatelets

Self-Healing and Flame-Retardant Modifications of Epoxy Resins by the Diels–Alder Release-Delivery Strategy for a High-Efficiency and Green Application

Graphene Oxide-Modified Epoxy Asphalt Bond Coats with Enhanced Bonding Properties

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