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The continuous upgrading of electronic technology has facilitated the integration and miniaturization of electronic and electrical equipment, as well as putting great pressure on the multifunctional demand for internal materials. Developing insulating materials with both low permittivity and high thermal conductivity has become imperative. This perspective focuses on polyimide (PI), which is the top material of the polymer material pyramid, discusses the characteristic parameters that affect its dielectric property and thermal conductivity. A series of basic schemes to regulate the dielectric/thermal properties of PI are summarized, revealing the bottlenecks and drawbacks of the current research. Future development trends of PIs featured low permittivity-high thermal conductivity are anticipated, and novel ideas are proposed for the development of new generation of multifunctional PIs. [ABSTRACT FROM AUTHOR]

Integration of controllable deformation with excellent thermal stability, mechanical, and insulation properties can greatly expand the versatility of smart polyimides (PIs). However, the unique molecular structure of PI makes it difficult for its molecular chain to move, which is not conducive to the reversible transformation of highly stable PI under environmental conditions. In this study, a PI film integrating shape memory and photo deformation is prepared by constructing a chemical network with PI oligomer as the hard, hexamethylene diisocyanate (HDI) as the soft, and azobenzene as the functional chain segment. The PI films still have a high glass transition temperature Tg ~ 225°C, a high Young's modulus E ~ 3.5 GPa, and a good breakdown strength Eb ~ 176 kV/mm. Moreover, as the network point of the chemical network, the trifunctional crosslinking agent makes the PI produce the shape memory effect induced by light and heat. UV light can drive crosslinked photoresponsivity PI film to have special shape transformation under specific conditions, using azobenzene as photoresponsivity group. This study provides a new idea for the preparation of multifunctional PI, which makes it potentially applicable in the field of smart electric and electronic engineering. [ABSTRACT FROM AUTHOR]

Polyimide (PI) has excellent resistance to high or low temperatures due to its unique molecular structure, and is widely used in advanced electronics and power systems in extreme environments. In recent years, a small amount of studies have been published to modulate the dynamic behavior of PI such as self‐healable, recyclable, and degradable abilities by adjusting the structure of molecular chains and the composition of monomers. However, the conceptual design, formation conditions, and application prospects of dynamic PI are still unclear. In this paper, the new concepts and systems of dynamic PI are introduced from the perspective of the design of molecular structure, the development of regulating performance area, and the application of extreme insulation, based on recent work and other representative work. Specifically, this work appeals to researchers involved in PI synthesis, smart, dielectric, energy storage, and extreme insulation. [ABSTRACT FROM AUTHOR]

The insulation performance of oil-immersed paper bushings is prone to deteriorate, primarily due to moisture intrusion and thermal aging. The frequency domain spectroscopy (FDS) method is commonly employed to assess the insulation condition of the bushing. However, identifying and extracting relaxation polarization information from the low-frequency region of the FDS curve can be challenging, and there is little research about the condition evaluation under the combined effects of aging states and moisture content. To address this issue, this article uses the Taylor formula mathematical model to extract characteristic parameters from the dielectric modulus curve of OIP bushings and uses the KNN algorithm to achieve the evaluation of aging and moisture status. Then, the effectiveness and accuracy of the proposed method are validated on three field OIP bushings. The results demonstrate that the evaluation accuracy of the proposed method exceeds 83%, which has significant advantages compared to other classification algorithms. The innovation of this article lies in extracting new feature parameters and combining them with intelligent classification algorithms to evaluate the moisture and aging state of the bushing. [ABSTRACT FROM AUTHOR]