After long-term hygrothermal ageing, the bonding between fibers and resin in basalt fiber composites is prone to damage, making the development of hygrothermal ageing-resistant coatings become a key factor in advancing the application of basalt fibers. In this paper, the construction of hygrothermal-resistant sizing coatings was carried out through molecular dynamics simulation and first-principles molecular dynamics simulation. The effects of four types of epoxy emulsions—diglycidyl ether of bisphenol A (DGEBA), dimer acid-modified epoxy resin (DAER), hydrogenated bisphenol A epoxy resin (HBPA), and cycloaliphatic epoxy resin (CER)—used as sizing coatings for basalt fibers on the hygrothermal resistance of basalt fiber reinforced polymer (BFRP) were simulated and analyzed. The results show that owing to the low polarity and high energy gap of the primary crosslinking structure formed by CER and MHHPA, the CER-modified basalt fiber (BF-CER) imparts the best insulation performance to the composite; meanwhile, its high interfacial binding energy results in the highest flexural strength among the four types of samples. Due to its strong dielectric barrier capability and high binding energy stability, BF-CER displays the best stability in mechanical and electrical properties within 20 h of ageing. During ageing from 20 h to 120 h, the HBPA-modified basalt fiber shows the highest stability owing to its lower degree of hygrothermal degradation. In summary, BF-CER possesses the most outstanding hygrothermal ageing resistance.

Insulation interface defects are a major cause of cable terminal failure in extreme cold environments, and the stress state at the epoxy resin/silicone rubber interface directly determines the mechanical integrity and the stability of thermal and electrical properties of the cable terminal interface. In this study, a simplified model of the epoxy resin/silicone rubber interface in cable terminals was first designed based on the actual assembly process. The interface stress of this simplified model under extreme cold conditions was calculated using finite element analysis. Then, a quantitative relationship model between the interface stress and the reflection coefficient of epoxy/silicone rubber composite samples was established using an ultrasonic pulse detection system. Finally, a simplified terminal model was fabricated, and ultrasonic pulse detection experiments were carried out under extreme cold environments ranging from 20℃ to -40℃. The interface stresses at different temperatures were inverted using the quantitative model and compared with the simulation results. The results show that the ultrasonic velocity in epoxy resin increases linearly with the decrease of temperature, and the increase rate is 3.446 7 m/(s·℃). During the process of cooling from 20℃ to -40℃, the interface stress of epoxy/silicone rubber decreases significantly due to the loss of interference caused by the temperature drop.The error between the simulation and experimental results remains around 5%, confirming the reliability of the proposed interface stress back-calculation method under extreme cold environments.

Porcelain insulators are critical components of transmission lines, and their defects will directly threaten the safe and stable operation of power systems. Taking XP-160 porcelain insulators as the research object, we proposed a numerical simulation method for microwave detection of porcelain insulator defects. The variation patterns of the reflection coefficient and transmission coefficient under crack and metal inclusion defects were analyzed and compared, the optimal detection method and detection frequency were obtained, and the detection mechanism was analyzed. The results show that at a frequency of 20 GHz, the microwave reflection method with the antenna placed horizontally achieves the best detection performance for both types of defects, and defect orientation can be identified through rotational detection. Internal defects cause changes in the nearby electromagnetic field distribution, which in turn leads to variations in the characteristic parameters.

This study aimed to establish a rapid on-site detection method for the mechanical properties of cross-linked polyethylene (XLPE) cable insulation based on near-infrared spectroscopy. Considering the high light transmittance of XLPE insulation and taking into account spectral repeatability and signal-to-noise ratio, a transflective "6+1" fiber optic acquisition probe and a supporting detection device were developed. The near-infrared spectra of 60 cable samples were collected, and the influence of spectral baseline drift was eliminated by second-order derivative pretreatment. The elongation at break and tensile strength of the samples were measured according to GB/T 2951.11—2008 and used as reference values for modeling, and the repeatability of the reference data was verified. The preprocessed spectral matrix was correlated with the reference values using partial least squares (PLS) regression, and a multivariate calibration model for the mechanical properties of XLPE insulation was established. The results show that the cross-validation standard errors of the model for elongation at break and tensile strength are 12.16 and 0.55, respectively. When five blind samples were prepared by the model, the relative deviations between the predicted results and the reference values are all less than 5%, demonstrating that the model can effectively achieve rapid assessment of the mechanical properties of XLPE insulation.

Polyimide (PI), as a type of special polymer materials with excellent comprehensive properties, is widely used in various fields such as electronics and electrical engineering, electrical insulation, and aerospace. However, with the rapid advancement of 5G/6G high-frequency communication technologies, higher requirements have been put forward on the dielectric properties of dielectric layer materials in electronic devices. PI faces significant challenges, including its inherently high dielectric constant (D_k) and dielectric loss (D_f), as well as relatively high-water absorption, which restrict its further development in related applications. In this paper, the intrinsic action mechanism of D_k and D_f of polymers under electric field was introduced at first, and then the main research progress of low-D_k and low-D_f polyimide films in recent years, as well as the modification strategies of polymer molecular structure and dielectric properties were reviewed respectively. Finally, the research direction of low-D_k and low-D_f polyimide films was summarized and prospected.

Functional inorganic dielectric materials with low dielectric constants (ε_r<10), represented by ceramic materials, glass-ceramic composites, and microcrystalline glass, play an irreplaceable role in cutting-edge technologies such as high-frequency and high-speed communications, high-density integrated packaging, and high-reliability electronic devices. Among these, high-temperature co-fired ceramic (HTCC) technology employs high-strength alumina ceramics, high thermal conductivity aluminum nitride ceramics, or low-dielectric-constant silicon-based ceramics as insulating packaging materials. Low-temperature/ultra-low-temperature co-fired ceramic (LTCC/ULTCC) technology employs intrinsically low-sintering-temperature ceramics, sintering aid-reduced sintering-temperature ceramics, glass-ceramic composites, and microcrystalline glass as packaging materials. This paper elaborated and summarized the above low-dielectric-constant inorganic dielectric materials, and prospected the application of machine learning (ML) in the prediction and design of novel low-dielectric and low-loss packaging materials, providing a new route for the development of related systems.

The rapid development of 5G/6G high-frequency communication technology has placed unprecedented demands on dielectric materials: they require an extremely low dielectric constant (D_k<2.8) and dielectric loss (D_f<10^-3). Moreover, new low-dielectric materials must possess excellent hydrophobicity to ensure the long-term stability of their dielectric properties. The intrinsic dielectric properties of traditional materials struggle to meet these requirements, while post-modification strategies like pore generation often sacrifice mechanical performance. This paper systematically discussed a novel design strategy for dielectric materials based on the “long alkyl chain-induced effect”, elaborated the synergistic mechanism of reducing the dielectric constant and loss through free volume effects, polarity control, and trap mechanisms, and emphatically introduced successful implementation in three major polymer systems: fluorene-based polymers, alkylphenyl polymers, and bio-based cardanol polymers. In view of the excellent hydrophobic performance of the as-designed materials, this paper also discussed their potential in ensuring the long-term stability of dielectric properties. Finally, the future development trends and existing challenges in this research field were prospected.

Low dielectric polymer materials play a critical role in modern microelectronics, telecommunications, power systems, and aerospace industries, and the development of their preparation technologies continuously drives the progress of related industries. The research background of low dielectric polymer material fabrication techniques was elaborated in this paper. Beginning with material design principles, the relationship between molecular structures, functional group characteristics, and dielectric properties was deeply analyzed. The research progress of low-dielectric polymers, including polyolefins, fluorinated polymers, silicon-containing polymers, and aromatic polymers, was systematically classified and discussed, aiming to provide a reference for further research and application of low-dielectric polymer materials.

With the rapid progress of high-speed communication as well as millimeter-wave and sub-terahertz (sub-THz) technologies, polymeric insulating materials with low dielectric constant (D_k), low dielectric dissipation factor (D_f), and tunable molecular structures are increasingly required in the tens-to-hundreds of GHz range. In recent years, researches on the high-frequency dielectric properties of aromatic and fluorinated polyimides (PIs) have expanded from simple parameter reporting to multiple perspectives, including polarization mechanism analysis, molecular structure control, humidity dependence, and correlations with optical properties. This review provided a systematic overview of the dielectric behavior of PIs above 10 GHz, with a focus on the dominant frequency regimes of dipolar and electronic polarizations, the influence of humidity on D_k and D_f, and the modulating effects of fluorine content, free volume, and polar functional group fraction on dielectric dispersion. While ensuring the thermal stability, chemical resistance, and mechanical reliability, the review further summarized molecular design strategies for reducing D_k and D_f, and proposed future directions for material optimization toward millimeter-wave and sub-THz applications.

The rapid development of 5G communication and millimeter-wave radar technology has imposed increasingly high requirements on the high-frequency performance of printed circuit boards (PCBs). Polytetrafluoroethylene (PTFE) stands out as a preferred material for microwave substrates due to its excellent dielectric properties, low water absorption, and outstanding chemical and thermal stability. This review categorized commercial products into five types based on their composite structures: woven glass fiber reinforced type, woven glass fiber reinforced-ceramic filled type, random short glass fiber reinforced type, random short glass fiber reinforced-ceramic filled type, and ceramic filled type, and discussed the representative products, key characteristics, fabrication processes, and technical advantages and disadvantages of each category. Furthermore, the paper provided a systematic overview of recent research progress on the effects of PTFE resin properties, filler type, content, morphology, and surface treatment on the performance of composite. PTFE-based composites are expected to maintain their dominant position in the millimeter-wave and even terahertz frequency bands for the foreseeable future. Looking ahead, breakthroughs in optimizing processing techniques, developing high-performance PTFE resins, innovating functional fillers, and conducting fundamental interface research are essential to narrow the performance gap with imported products and thereby advance China's microwave substrate materials industry.