With the development of economy and technology, the demand of safer and more stable packaging materials for electronic devices has increased. Traditional polyimide (PI) base materials are extensively used due to their excellent mechanical and heat-resistant properties. In this study, a novel fluorinated polyimide (FPI) porous composite film was developed by introducing fluorine groups and a porous structure into polyimide, along with adding the flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Experimental results demonstrate that under 80%RH of ambient humidity and 5% of DOPO mass fraction, the new FPI porous composite film exhibits uniform and regularly distributed pore size, excellent mechanical properties, and lower water absorption. The incorporation of flame retardant DOPO forms a protective phosphorus-containing layer on the film surface, which significantly improves the flame retardancy and hydrophobic properties of film. This research provides a new material with enhanced safety for the packaging of electronic devices, which is expected to play a crucial role in improving the stability and safety of electronic equipment.

Under the high temperature conditions (90, 105, 120, and 135°C), accelerated ageing tests of nitrile rubber (NBR) were conducted in hot air, hot oil, hot air compression, and hot oil compression. The ageing mechanisms were investigated through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG), and scanning electron microscopy (SEM), and the effects of ageing temperature, time, and deformation conditions on the ageing behavior of NBR were revealed. The results indicate that crosslinking, oxidation, and chain-breaking reactions occur during the ageing process of NBR, and the crosslinking reaction is the predominant reaction. After ageing at 120°C, grooves appear on the surface of NBR, and after ageing at 135°C, defects such as holes and damages appear on the surface. In the early stage of ageing, transformer oil has a suppressive effect on the increase of permanent deformation under compression. In the later stage of ageing, transformer oil plays a promote role for the decrease of tensile strength, and the higher the temperature, the more obvious the effect.

Meta-aramid insulation paper is widely used in transformers and high-voltage bushings due to its excellent dielectric and mechanical properties, but its low thermal conductivity limits its application in high thermal load environments. To enhance the thermal conductivity of nano-filler/aramid insulation paper, this study employed simulation-guided experimental design to calculate the thermal conductivity of aramid simulation models. Three nano-fillers with excellent thermal conductivity properties, namely nano SiO₂ (KH570), nano TiO₂, and nano C₃N₄, were screened out. The mechanical and insulation performance of laboratory composite aramid paper hand sheets were compared, and the optimal filling amount was determined. Further, the influence of nano-fillers on the thermal conductivity of composite aramid paper was explored, and their inherent thermal conduction mechanism was analyzed. The results show that the optimal addition amounts of three nano-fillers are: nano SiO₂ (KH570) at 10%, nano TiO₂ at 4%, nano C₃N₄ at 4%. Through thermal conductivity testing, nano C₃N₄ is determined to be the optimal nano-filler, and the composite aramid paper with 4% of nano C₃N₄ showing an increase in elastic modulus by 135%, Young's modulus by 198%, electric strength by 60.24%, volume resistivity by 3 713%, and thermal conductivity by 304.31% compared with pure aramid paper.

To address the challenges of epoxy resins in electrical insulation and flame-retardant applications, a phosphorus-containing bio-based flame-retardant resin—bis(methacryloyloxy-4-hydroxy-3-methoxyphenyl) phenyl phosphate (DGEBDB) was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and renewable vanillin, and cured materials were prepared through blending it (0%, 25%, 50%, and 75%) with bisphenol A epoxy resin (DGEBA). Their flame retardancy, thermal properties, mechnical properties, and electrical properties were analyzed. The results show that when the mass fraction of DGEBDB is 75%, the limiting oxygen index (LOI) of epoxy bending system increases from 22.6% to 34.2%, and the flame retardant grade achieves V-0 in UL 94 tests. Cone calorimetry reveals that the DGEBDB can reduce the heat release rate (HRR) and total heat release (THR), showing excellent fire suppression. Electrical properties tests show that the electrical properties of the cured epoxy maintain good when the mass fraction of DGEBDB is as high as 75%, which ensures the reliability of DGEBDB in electrical application. Mechanical properties indicate that with the increase of DGEBDB content, the flexural strength and tensile strength increase, indicating an increase in structural integrity and load bearing capacity of the cured epoxy. Therefore, the addition of DGEBDB significantly enhances the flame retardantcy of composite, while maintaining the excellent thermal, mechanical, and electrical properties of epoxy resin, and when the mass fraction of DGEBDB is 25%, the overall performance is the best, which has a better prospect for practical applications.

In order to reveal the influence of external electric field on the internal molecular structure characteristics of silicone rubber insulation materials at the micro level, this paper used molecular simulation and quantum chemistry methods to explore the changes in the microstructure and space charge characteristics of silicone rubber under the action of external electric field. The results show that with the increase of electric field strength, the total energy of the silicone rubber molecule system decreases, the dipole moment and polarizability increase, and the C-Si bond inside the molecule becomes longer when subjected to the stretching effect of external electric field, resulting in a decrease of the stability of silicone rubber structure and affecting its mechanical and electrical properties. Under a higher electric field strength , the energy gap of the frontier orbitals decreases, and the reactive active sites of the silicone rubber molecular chain change, it causes of trap energy levels for the electron traps and hole traps in the frontier orbitals of the molecular chain to form different degrees of trap energy level distribution, and enhances the ability of silicone rubber to capture free electrons or injected charges in insulating materials. When the electric field reaches the critical value of 12.75×10³ kV/mm, the molecular structure of silicone rubber is disrupted and causes changes in the infrared spectrum.

The vacuum surface insulation performance of insulation material used in radiation environment simulation devices will be significantly affected by long-term radiation exposure. By conducting irradiation ageing experiments of different doses of gamma ray on polymethyl methacrylate (PMMA) materials, the variation law of surface microstructure and electrical performance parameters of PMMA materials with gamma ray irradiation dose was studied. The results show that when irradiated under a low-dose (0.1 kGy) gamma rays, the distribution of surface traps on the material is the main factor affecting the vacuum surface withstand voltage characteristics of PMMA the vacuum surface ageing voltage of PMMA increases by 11.7% compared to the unirradiated sample. When irradiated with high doses (greater than 1.0 kGy) of gamma rays, holes appear on the surface of PMMA material, and the local electric field intensity is distorted, becoming a "weak area" of vacuum surface insulation. Appropriate doses of gamma ray irradiation is helpful to improve the vacuum surface insulation performance of PMMA.

In order to realize the recycling and reuse of degraded glass fiber (d-GF), to obtain degraded glass fiber was obtained by chemical degradation method from the selected the 220 kV retired composite insulator core rod, and the mechanical, thermal, and microscopic differences between degraded glass fiber and ordinary glass fiber (GF) were compared. Then, polyethylene (PE) composite materials (d-GF/PE, GF/PF) reinforced with different contents of glass fiber were prepared to explore the reuse prospects of degraded glass fiber reinforced materials. The results show that silane coupling agent can realize the surface modification of degradable glass fiber, and the modification effect is slightly better than that of ordinary glass fiber. The surface of the degraded glass fiber is relatively rough, with scale like damage and a small amount of resin residue in some areas, but there is no obvious erosion or fracture phenomenon on the whole. The fracture stress distribution of degradable glass fiber is relatively discrete, and the average fracture stress is 1 520 MPa, which is 29.95% lower than that of ordinary glass fiber. The interface state between glass fiber and polyethylene matrix in d-GF/PE is good, under the same glass fiber content, the difference in maximum fracture stress between d-GF/PE and GF/PF is only 2.15 MPa.

The heat resistance of ethylene propylene diene monomer (EPDM) decreases significantly after thermo-oxidative ageing, resulting in poorer performance and shorter service life of products made from it. This paper reviews the research progress on improving the thermo-oxidative ageing resistance of EPDM at home and abroad. It introduces three main methods for improving the thermo-oxidative ageing resistance of EPDM, including selecting high thermal-resistant EPDM matrix, compounding with thermal-resistant rubber, and adding antioxidants. And it provides a brief outlook on future research directions for improving the thermo-oxidative ageing resistance of EPDM.

The traditional time-frequency domain reflection method (TFDR) is difficult to accurately obtain the time-frequency distribution of the acquired signal, which seriously reduces the location accuracy of cable defects. Therefore, a cable defect localization method based on Hilbert transform (HT) and TFDR was proposed in this paper. Firstly, the Gaussian frequency domain window function was introduced by Fourier digital filtering method to suppress the interference of the acquired signal. Then, the time-frequency distribution of incident traveling wave signal and reflect traveling wave signals were obtained by HT method. Finally, the instantaneous power spectrum of time-frequency distribution was used to characterize the time-frequency energy focusing characteristics of the defect reflected traveling wave signal, and the defect position in the cable was located through the peak value of the final curve obtained. The results show that, compared with the traditional Wigner distribution method and synchronous compression transformation method, the traveling wave signal obtained by this method has higher time-frequency resolution and no cross term interference, which can locate local defects in cables more accurately.

The crystallinity of chopped fibers has an important impact on the mechanical strength, thermal shrinkage resistance, toughness, and other properties of aramid paper. To investigate the influence and mechanism of chopped fibers crystallinity on the properties of meta-aramid paper, meta-aramid papers with different crystallinity of chopped fibers were prepared by controlled variable method, and their mechanical properties, electrical properties, and thermodynamic properties were tested. The results show that the electric strength of meta-aramid papers is not significantly affected by the crystallinity of chopped fibers, it is mainly determined by precipitated fibers. The tensile index of meta-aramid papers is almost not affected by the crystallinity of chopped fibers before hot-pressing, but increases with the increase of the crystallinity of chopped fibers after hot-pressing. When the crystallinity of chopped fibers increases from 27.19% to 47.91%, the tensile index of papers enhances from 46.2 N·m/g to 58.0 N·m/g. In addition, the thermal shrinkage resistance of papers is closely related to the crystallinity of chopped fibers. When the crystallinity of chopped fibers increases from 27.19% to 47.91%, the thermal shrinkage rate of papers decreases from 4.8% to 1.3%.