Abstract
The advocacy of carbon neutrality and circular economy encourages people to pursue self-healing and recycling of glassy thermoset polymers in a more realistic and energy-saving manner, the best being intrinsic healing under room temperature. However, the high mechanical robustness and healing ability are mutually exclusive because of their completely opposite requirements for the mobility of the polymer networks. Here, we report a dual-cross-linked network by slightly coupling the low-molecular-weight branched polyethylenimine with an ester-containing epoxy monomer in a nonstoichiometric proportion. The highly mobile and dense noncovalent hydrogen bonds at the chain branches and ends can not only complement the mechanical robustness (tensile strength of 61.6 MPa, elastic modulus of 1.6 GPa, and toughness of 19.2 MJ/m3) but also endow the glassy thermoset polymer (Tg > 40 °C) with intrinsic self-healing ability (healing efficiency > 84%) at 20 °C. Moreover, the resultant covalent adaptive network makes the thermoset polymer stable to high temperatures and solvents, yet it is readily dissolved in ethylene glycol through internal catalyzed transesterification. The application to room temperature delamination healing and carbon fiber recycling was demonstrated as a proof-of-concept.
Highlights
The concept of carbon neutrality and circular economy is sweeping the world on account of the growing problems of oil crises and environmental issues
The curing kinetics was studied by differential scanning calorimetry (DSC) at different heating rates (Figure S1)
The tensile strength (411.0 ± 7.7 MPa) and elongation at break (8.3 ± 0.3%) of the regenerated composite are almost the same as those of the original ones (411.4 ± 7.7 MPa and 8.8 ± 0.3%, respectively) (Table S4), suggesting full recovery of the mechanical performance. These results demonstrate that the DCN−PEI-based composite laminates exhibit great recyclability under mild conditions, and the recycled carbon fibers hold their initial textile structure, surface characteristic, and mechanical properties, which can be reused to fabricate composite laminates without degradation of the reinforcing effect
Summary
The concept of carbon neutrality and circular economy is sweeping the world on account of the growing problems of oil crises and environmental issues. The healing process can be varied from cold to high temperatures depending on the reactivity of the healing agents These kinds of self-healing materials have some inherent problems such as limited healing cycles, short shield life, high viscous precursor mixture, and degraded mechanical performance of resultant materials due to the addition of a large quantity of weak microcapsules, which make them difficult to fabricate high-performance self-healable structural composites with complex construction, such as laminates. The noncovalent cross-linking of networks always means low mechanical strength, and their tensile strengths are all below 40 MPa (tested at a stretching rate of 10 mm/min) These results demonstrate the limited application of these polymers in heavy load-carrying structures and harsh conditions. Healing of the glass fiber reinforced laminate at room temperature, and recycling of the carbon fibers in the carbon fiber reinforced laminate with mild recycling conditions were demonstrated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
