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Polymer composites with high energy density have been of great interest to scientists for a long time, and this accounts for a great wealth of experimental data that are available for interpretation. One of the important phenomena is the variation rate of the permittivity of composites, which always deviates from the linear increase and rises steeply toward the high concentration. Interestingly, the critical transition concentration is always located in the range of 20 vol. %–25 vol. %, but still far less than the common percolation threshold of composites. Through the analysis of the local electric field distribution and surface polarized charges distribution, the phenomenon is successfully interpreted as the effect of the electrostatic interactions between the adjacent polarized particles. Two specified composite configurations (BCC and FCC) are designed, and their dielectric properties have been systematically studied with the help of the finite element method and the phase field method. The simulation results indicate that the strength of the particles' interaction is short-range effective and depends closely on the gap distance between adjacent particles. When the gap distance is smaller than 0.8 times the radius of the particles, which is tantamount to the concentration larger than 20 vol. % and 25 vol. % for BCC and FCC, respectively, the electrostatic interaction of the particles is rather significant, resulting in an additional contribution on the variation of the dielectric properties of composites and vice versa. The synchronous variation tendency between the simulation results and experimental measurements demonstrates the effect of electrostatic interaction on the dielectric properties of composites. [ABSTRACT FROM AUTHOR]

Recyclability and self‐healing are two most critical factors in developing sustainable polymers to deal with environmental pollution and resource waste. In this work, a dynamic cross‐linked polyimide insulation film with full closed‐loop recyclability is successfully prepared, which also possesses good self‐healing ability after being mechanical/electrical damaged depending on the Schiff base dynamic covalent bonds. The recycled and self‐healed polyimide film still maintain its good tensile strength (σt) >60 MPa with Young's modulus (E) >4 GPa, high thermal stability with glass transition temperature (Tg) >220 °C, and outstanding insulation property with breakdown strength (E0) >358 kV mm−1, making it a very promising low energy consumption and high temperature resistant insulation material. The strategy of using Schiff base dynamic covalent bonds for reversible repairing the structure of high Tg polyimides promotes the wider application of such sustainable and recyclable material in the field of electrical power and micro‐electronics. [ABSTRACT FROM AUTHOR]

In this work, a small amount of ionic liquids (ILs, 1-vinyl-3-ethylimidazolium tetrafluoroborate) was used to modify tungsten disulfide (WS2), and then, the modified WS2 was mixed with ethylene propylene diene monomer (EPDM) to obtain IL-WS2/EPDM composites with different IL contents. The content of WS2 in composites was determined from the result of our previous work. The nonlinear electrical conductivity of composites at 25 °C, 50 °C, and 80 °C was measured and analyzed subsequently. A small amount of ILs has an influence on the nonlinear property of composites, and the inflection point of the ternary composite can be controlled by changing IL contents. The direct current (DC) breakdown strength and thermal conductivity of composites were also measured and researched. Addition of ILs would decrease the breakdown strength of IL-WS2/EPDM composites. [ABSTRACT FROM AUTHOR]

Increasing the actuation characteristics of dielectric elastomer actuators (DEAs) under low electric field strength without compromising the elasticity and breakdown strength is still one of the great challenges in application field. Herein, we propose a simple, efficient, and controllable strategy to prepare dielectric elastomers with intrinsically good integrated properties by introducing styrene ethylene butylene styrene (SEBS) in thermoplastic polyurethane (TPU). Combined with experiments and molecular dynamics simulation, we find that the SEBS is uniformly dispersed in TPU matrix and a good interface structure is formed by pi–pi interaction and entanglement. The above characteristics lead to the destruction of the hydrogen bond network of TPU and the formation of single aggregation structure. Consequently, much decreased Young's modulus (Y) and enhanced breakdown field (Ebr) are achieved. Especially, when the content of SEBS is 4.76 wt%, the blend shows a desirable Y of 2.4 MPa and a much improved Ebr (118 kV mm−1), which is about 59% lower and 42% higher than those of TPU, respectively. As a result, the maximum electrical strain area of the dielectric blend elastomer reaches 4.7%, which is 250% higher than that of pure TPU under the same electric field strength. [ABSTRACT FROM AUTHOR]