According to the application requirements of thermoplastic black polyimide film in the field of advanced flexible copper clad laminate (FCCL), three organo-soluble polyimide (SPI) resins were prepared from an aromatic diamine monomer containing chromogenic imine (-NH-) group, 4,4′-diaminodiphenylamine (NDA) and various dianhydrides, including 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), and hydrogenated 3,3′,4,4′- biphenyltetracarboxylic dianhydride (HBPDA) by polymerization. Then PI films were prepared from SPI/DMAc solution at relatively low temperature (80-250℃), and the effects of the above characteristic groups on the optical properties, thermal properties, and electrical properties of PI films were studied systematically. The results show that the SPI resin has good solubility in polar aprotic solvents such as N-methylpyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). The SPI films show intrinsically deep color, the transmittance value at 550 nm of wavelength (T₅₀₀) is lower than 5%, and the lightness (L^*) is below 60. The PI films have good thermal stabilities, the glass transition temperatures (T_g) is up to 375.9℃ and the 5% weight loss temperatures (T_5%) is over 500℃ in nitrogen. Besides, the PI films exhibit good electrical insulating properties, the volume resistivities (ρ_v) is higher than 10¹⁵ Ω·cm.

In order to prepare polyimide (PI) films with high order degree and stable thermomechanical properties, pyromellitic dianhydride (PMDA) monomer was introduced into biphenyltetracarboxylic acid dianhydride-p-phenylenediamine (BPDA-PDA) system, and PI films were prepared by random copolymerization method. The aggregation structure and physical properties of the PI films were analyzed by XRD, TMA, DMA, TGA, prism coupling instrument, and universal testing machine. The results show that different dianhydride composition has a significant effect on the aggregation structure and thermal mechanical properties of PI films. With the increase of PMDA-PDA segment composition, the molecular chain order degree increases, and the molecular chain spacing decreases from 0.469 nm to 0.436 nm. The birefringence value shows an upward trend in the range of 0.18‒0.22. The glass transition temperature (T_g) decreases at first and then increases in the range of 379.86‒439.05℃. The thermal expansion coefficient (CTE) increases at first and then decreases in the range of 0‒7×10^-6 K^-1. The tensile strength and 5% thermal decomposition temperature (T_5%) show a downward trend in the range of 166‒225 MPa and 576.8‒590.4℃, respectively. When the mole fraction of PMDA is 60%, the PI film has excellent comprehensive properties with 0.22 of birefringence, 439.05℃ of T_g, 0.012 5×10^-6 K^-1 of CTE, 302.5℃ of heat resistance index(T_HRI) , and 576.8℃ of T_5%.

According to the application requirements of low thermal expansion (low-CTE) for colorless and transparent polyimide (CPI) films, the structural design and synthesis of methyl-substituted aromatic diamine monomers containing rigid amide bonds in the main chain, including 2-methyl-4,4′-diaminobenzanilide (MeDABA) and 2,3′-dimethyl-4,4′-diaminobenzanilide (MMDABA), were performed. Firstly, the dinitro compounds were prepared by the amide reactions using the methyl-substituted p-nitrobenzoic acid or methyl-substituted p-nitroaniline as raw material. Then, a series of new diamine compounds were obtained by the reduction of hydrazine hydrate under the catalysis of Pd/C. The chemical structures of the diamine monomers were characterized by differential scanning calorimetric analysis (DSC), Fourier infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), mass spectrometry (MS), and elemental analysis (EA). The results show that the aromatic diamine monomers with expected structure are prepared successfully.

This article started from the composition and classification of silicone grease to get access to the performance requirements according to the demand of cable accessories. And then the two typical common grease used in cable accessories was described, including normal silicone grease and silicone fluoride grease. At last, the research status of coated silicone grease used for cable accessories and the selecting method of silicone grease were summarized.

The ageing failure of composite insulators in coastal areas has always brought great hidden danger to the safe and stable operation of power grid in coastal areas, and it is also the key and difficult point in the operation and maintenance management of composite insulators. In this paper, the post composite insulators used in substations with different operation years were studied, and the relationship between the hydrophobicity and the operation years was analyzed. The results show that the hydrophobicity is closely related to the high voltage environment, insulator surface orientation, and other factors, and when the operation time of insulators reaches 7 years, the hydrophobicity declines sharply.

A kind of composite foam material was prepared by adding hollow polymer microbeads to the organosilicon modified resin, and then the composite foam material was used as the internal filling material for the composite insulating cross-arm. The influence rule of the microbead type and filling content on the density, hydrophobicity, dielectric loss factor, and electric strength of the composite foam material was analyzed. The results show that the filling of organic microbeads can effectively reduce the density of the composite foam, and the density of the sample filled with 920DET40d25 microbeads can be reduced to 0.5538 g/cm³. Because there are more hydrophobic groups in the microbeads, the hydrophobicity of the composite foam material is enhanced. With the increase of the microbead content, the electric strength of composite foam material shows a downward trend, but the insulation strength of all the samples still meets the requirements of the internal insulation material for composite cross-arms. Considering the requirements of the density and insulation strength of the composite foam material, the sample filled with 920DET40d25 microbeads with a mass fraction of 2.5% meets the application requirements.

Due to artificial operation and poor sealing performance during the assembly of oil-related equipment in some substation, the shed on composite insulator used in the auxiliary equipment may deform due to the contact with insulating oil. In order to further study the influence of insulating oil on the composite insulator shed and analyze the cause of its deformation, we used insulating oil to treat silicone rubber for shed, and investigated its volume change, chemical structure, hydrophobicity, mechanical properties, and electrical properties. The results show that the insulation oil increases the volume of silicone rubber, while decreases its elongation at break, tensile strength, tear strength, and hardness, which relates to the swelling of silicone rubber. According to the study, using oil dropping device and insulator to simulate the deforming process of the shed, we propose a method of recovering the deformation of the shed by heat treatment.

A triethoxyacetylenic silane (TEOAS) was synthesized to treat the surface of hydroxylated multiwalled carbon nanotubes (MWCNTs), and then the MWCNTs-T was obtained and characterized. PSA/MWCNTs and PSA/MWCNTs-T composite resins were prepared using solution method by mixing silicon-containing polyarylacetylene (PSA) with MWCNTs and MWCNTs-T, respectively. The thermal conductivity, thermal stability, electric insulation, and bending properties of the PSA/MWCNTs and PSA/MWCNTs-T composites were investigated. The results show that TEOAS was grafted on the surface of MWCNTs successfully, and MWCNTs-T is compatible with PSA matrix. The thermal conductivity of the composites increases with the increase of the mass fraction of MWCNTs and MWCNTs-T. The effect of MWCNTs-T is more obvious, with the mass fraction of 2%, the thermal conductivity of PSA/MWCNTs-T reaches 0.62 W/(m·K), which is 3 times as higher as that of PSA. The introduction of MWCNTs and MWCNTs-T can decrease the thermal stability and bending properties of PSA, the effect of MWCNTs-T is smaller than that of MWCNTs. The glass transition temperature of the PSA/MWCNTs is higher than 500℃, the electrical resistivity of the composite resin decreases linearly with the increase of frequency, while is still higher than 10⁸ Ω·cm at 10⁶ Hz.

Bird damage is an important factor affecting the safe operation of transmission lines. In order to quantitatively analyze the spatial electric field distribution of bird droppings near insulators, we carried out simulation and calculation on the bird droppings flashover of 110 kV composite insulators, and studied the influence of different factors on the electric field. The results show that the longer the continuous channel of bird droppings, and the closer it is to the insulator, the more probable that flashover occurs. The existence of grading ring shortens the distance between the high and low voltage ends, which will increase the flashover probability; the dropping path of bird droppings has a great influence on the flashover probability, and the flashover probability is the lowest when the bird dropping is on the different surface of the transmission line. Finally, combined with the simulation results, new protection range of bird droppings is proposed to give some advice for protecting transmission line from bird damage.

Silicone rubber/carbon iron powder composite was physically modified by adding hexagonal boron nitride (h-BN) through melt blending, and the effects of h-BN on the mechanical properties, magnetic permeability, thermal conductivity, and thermal ageing properties of the composite were analyzed. The results show that h-BN well distributes in the composite, and it has good compatibility with silicone rubber matrix. The introduction of h-BN can effectively increase the tensile strength of the composite, while decrease the magnetic permeability. When the adding amount of h-BN is more than 20 phr, the thermal conductivity increases effectively. Under the continuous thermal ageing, the tensile strength of the composite increases at first and then decreases, while the elongation at break decreases continuously.