Insulating Silicones Based on Dynamic Hindered Urea Bonds with High Dielectric Healability and Recyclability

Abstract

Silicone-containing dynamically hindered urea bonds are developed as a smart insulating material for power equipment and electronic devices. In this work, silicones are constructed by isocyanate−piperazine-based dynamic bonds with cross-linking degree adjusted by glycerol. Healing and recycling based on dielectric and insulating properties are mainly emphasized in this study. We find that dynamic bonds not only heal the cut-damaged feature of the silicone but also enable dielectric property recovery. A healing efficiency above 95% and a recycling efficiency above 90% based on insulation performance are achieved. After recycling, cross-linked silicone exhibits only a slight variation in permittivity and tan δ, while linear silicone shows an apparent increase. Insulation performance of materials with different cross-linking agent concentrations is also investigated. A higher cross-linking degree was found to further improve insulation properties but reduces the recycling efficiency. Importantly, the developed silicones exhibit high intrinsic insulation properties, comparable to commercial silicone materials, which are very attractive for electrical applications.

Design and characterization of molecular, crystal and interfacial structures of PVDF-based dielectric nanocomposites for electric energy storage

“…Finally, Bi et.al reported that the highly insulating SiO 2 layer can efficiently hinder from forming the current channels to enhance the breakdown strength and optimize the microstructure and dielectric response to improve the energy store performances. 2 The breakdown strength of PVDF/BT@SiO 2 nanocomposites (580 kV mm À1 ) was significantly higher than that of PVDF/BT nanocomposites (258 kV mm À1 ). The energy density of the unmodified BT-based nanocomposites was 4.12 J cm À3 at 205 kV mm À1 .…”

“…The development of sustainable, [1][2][3] low-cost 4,5 and eco-friendly power conversion 6,7 and storage systems [8][9][10] is an urgent demand for the exploitation of high-density polymer-based dielectric materials. The dramatic improvement of the dielectric permittivity and energy density of dielectric polymers is not only beneficial for reducing the volume and weight of energy storage and conversion devices, but also ensuring that large electrical machines can work under stable conditions.…”

Dynamic covalent polymers enabled by reversible isocyanate chemistry

“…As discussed above, urea bonds are usually more stable than urethane bonds, leading to the requirement of high temperatures, extra nucleophiles, or catalysts to promote reversibility. 72,80,[149][150][151][152] Interestingly, the dynamicity of urea bonds can be dramatically expedited by delicately regulating the structures of nucleophilic moieties. Therefore, hindered urea bonds (HUBs), 55,153 pyrazole-urea bonds (PzUBs), 71 acylhydrazide-urea bonds 154 have been developed for the design of dynamic covalent polymers.…”

Dynamic poly(hindered urea) hybrid network materials crosslinked with reactive methacrylate polymer

“…Typical examples include aliphatic N,N′-di-t-butylethane-1,2-diamine reacting with various triols [26][27][28] and triisocyanates, [29][30][31][32] 2-t-butylaminoethanol reacting with triisocynates, 33,34 and aromatic N,N′-di-t-butyl-p-xylylenediamine reacting with a triol. 35 Along with the t-butylamino group, piperazine [36][37][38][39][40] and pyrazole groups [41][42][43] have also been explored to fabricate dynamic poly(urethane-urea) networks.…”