Abstract
Self-healing materials as a type of promising smart materials are gradually applied to electronics, biology, and engineering. In this study, we used in situ polymerization to make melamine-formaldehyde (MF) resin microcapsules to wrap the epoxy oxide as a repairing agent and Cu(MI)4Br2 as a latent-curing agent to protect epoxy oxide E-51 from broken melamine-formaldehyde resin microcapsules. In addition, graphene oxide was used as a reinforcing phase through its two-dimensional-layered structure to increase the tensile strength to 41.91 MPa, which is higher than the initial materials. The melamine-formaldehyde capsules and latent-curing agents were uniformly distributed in the materials according to the digital photos and scanning electron microscope (SEM) pictures. It is worth noting that the mechanical strength of the broken materials can be restored to 35.65 MPa after heating to 130°C for 2 h to repair the damage, and the self-healing efficiency reached up to 85.06%. Furthermore, we also fabricated the 4D printed material with a tensile strength of 50.93 MPa through a 3D printer. The obtained materials showed excellent repair effect, with a recovery rate of up to 87.22%. This study confirms that the designed self-healing system has potential applications in many areas due to its excellent self-healing performance, which provides valuable guidance for designing the 4D system.
Highlights
Smart materials have attracted widespread attention due to their shape and properties which can be altered with external environment changes, such as light, electricity, and magnetism (Wu et al, 2019). 3D printing smart materials, which are referred to as “4D printing,” change configurations over time
The structure of the self-healing system changes from disorder to layer, with the addition of graphene oxide, which will improve its toughness to a great extent (Ye et al, 2014)
The thermodynamic measurement indicated that the thermal decomposition temperature of the prepared microcapsule is 316◦C, which can largely protect the epoxy oxide inside the microcapsules from decomposition under high temperature
Summary
Smart materials have attracted widespread attention due to their shape and properties which can be altered with external environment changes, such as light, electricity, and magnetism (Wu et al, 2019). 3D printing smart materials, which are referred to as “4D printing,” change configurations over time. Smart materials have attracted widespread attention due to their shape and properties which can be altered with external environment changes, such as light, electricity, and magnetism (Wu et al, 2019). 4D printing has been used to develop many types of smart materials, such as shape-memory materials (Cheng et al, 2020), smart gel materials (Jang et al, 2020), and self-healing materials (Chen et al, 2016), which demonstrated great applications in the fields of biology (Aronsson et al, 2020; Kim et al, 2020), medicine (Javaid and Haleem, 2020; Lin et al, 2021), and bionics (Correa et al, 2020). Shiblee et al (2019) developed a shape memory hydrogel, which contains poly (N,Ndimethyl acrylamide-co-stearyl acrylate) [P(DMAAm-co-SA)], with the tensile strength of only 4.57 MPa. SAMs are characterized by high-tensile deformation and simple molding, their low-tensile strength limits their wide application (EnriquezCabrera et al, 2020).
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