IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
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2025
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IF 3.1
Shengrui Zhou,Zhang Li,Guan Wang,Qinkun Yang,Bilal Iqbal Ayubi
Under vacuum high-frequency electrical stress, polyimide (PI) films face severe surface discharge risks, which significantly affect their insulation stability in spacecraft dielectric systems. In this study, fluorinated polyimide (FPI) films with different fluorine contents were prepared, and a vacuum high-frequency surface discharge testing platform was established to systematically investigate their discharge characteristics. The results show that the introduction of fluorinated groups increases the surface electrical conductivity and thermal conductivity of the films. The discharge inception voltage increased from 1.88 kV for pure PI to 2.38 kV for 50% FPI, with a 26.6% increase. In addition, a non-equilibrium plasma model was constructed to dynamically simulate the formation process of discharge channels and the multiphysical evolution mechanisms. The results reveal that the front region of the discharge channel exhibits a coupled feature of “high density-low temperature-high reaction rate,” with significant electric field shielding and energy dissipation observed at the electron avalanche position. Fluorinated groups effectively suppress the establishment of surface discharge channels by reducing the secondary electron emission yield (SEEY) and dielectric constant, thereby weakening the electron multiplication effect and space charge accumulation. This study, from the perspectives of material regulation and physical mechanisms, provides theoretical support for optimizing the insulation performance of polyimide materials under vacuum high-frequency conditions.
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高影响因子
Journal of Environmental Chemical Engineering
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2025
·Vol. 14
·期 1
·120850
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IF 7.2
Xiaohua Tong,Enyang Zhang,Guangran Shao,Ming Yuan,Boyi Song,Wangqing Zhang
Polymer blending is a simple and cost-effective method to improve the gas separation performance of polyimide membranes, thereby potentially overcoming the inherent permeability/selectivity trade-off effect. However, its application still faces challenges, since only a few polymers are miscible with polyimides, and the mechanical property of the membranes usually reduces significantly after polymer blending. Herein, we prepare membranes by blending polyimide containing bulky isopropyl substituents with a small amount of polar polymers such as polyacrylonitrile (PAN). The resultant blend membranes using PAN as additive not only possess excellent gas separation performance but also maintain good mechanical property. For example, when 0.8 wt% PAN is added, the corresponding blend membrane displays a high CO 2 permeability of 632.2 Barrer and a high CO 2 /CH 4 selectivity of 23.4 under humidified condition, close to the 2008 Robeson upper bound, which is attributed to the formation of micro-phase separation structure within the blend membranes. Moreover, the tensile strength of the blend membranes using 0.8 wt% PAN as additive is only 12 % lower than that of the pure polyimide membrane. In addition, the blend membranes using PAN as additive show remarkable stability against physical aging and outstanding long-term operation stability, suggesting their great prospect for natural gas purification and biogas upgrading.
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高影响因子
Journal of Materials Research and Technology-JMR&T
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2025
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IF 6.6
Suhang Hou,Libo Wang,Lina Huang,Bo Wang,Weiwei Zhang,Jian Xie,Yihang Feng,Xinxin Cao,Aiguo Zhou
Polyimide (PI) is well known for its excellent thermal stability and mechanical strength, but its limited thermal conductivity and tribological performance restrict broader applications under harsh conditions. In this work, Ti 3 C 2 T x MXene nanosheets were incorporated into a PI matrix via in-situ polymerization to fabricate high-performance Ti 3 C 2 T x /PI nanocomposites with uniform filler dispersion. The thermal conductivity of the composite reached 1.99 W m −1 K −1 at 20 wt% MXene loading—an increase of 123% over pure PI. The thermal degradation temperature at 10% weight loss (T d10 ) also improved from 577.6 °C to 587.0 °C. Additionally, both storage modulus (E s ) and glass transition temperature (T g ) increased, indicating improved rigidity and thermal resistance. Tribological tests at room temperature and 200 °C revealed that the addition of 5 wt% MXene effectively reduced the coefficient of friction (COF) by 6.52% and 5.37%, respectively. The wear rate was also significantly reduced—by 83.41% at room temperature and 39.66% at 200 °C. These enhancements are attributed to the formation of a continuous and robust transfer film composed of MXene, oxides, and friction-induced organic products. This work provides a promising route for high-performance PI-based composites with improved thermal and tribological functionalities.
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高影响因子
ACS Applied Materials & Interfaces
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2025
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IF 8.2
Long Ni,Cuiqing Zhou,Lu Shen,Ke Yang,Yinfu Luo,Liwei Yan,Shuang Xia,Mei Liang,Shengtai Zhou,Huawei Zou
Lightweight porous materials with integrated cushioning and shock absorption, excellent thermal insulation, and hydrophobicity demonstrate a broad application prospect in high-end engineering sectors. Herein, the fabrication of lightweight polyimide foams (PIFs) containing trifluoromethyl and siloxane moieties was proposed by adopting copolymerization and microwave-assisted foaming processes. The synthesis and preparation of fluorine- and silicon-containing polyester ammonium salt (PEAS) precursor powders and subsequent PIFs, as well as the relationship and mechanism between structure and properties, were systematically explored. The construction of the anisotropic pore structure was attributed to the “bottom-up” directional foaming behavior of the microwave-assisted foaming process, which endowed PIFs with different traits with respect to the pore growth direction. The resulting copolymerized PIFs displayed low density (18.3–27.7 kg/m3), enhanced mechanical flexibility (compressive strength improvement of 26.2%, compression response rate between 97.5 and 99.1%), excellent thermal stability (T5% > 485.2 °C), and thermal insulation performance. Combining the micro/nano pore structure with the presence of hydrophobic trifluoromethyl and siloxane moieties, PIFs exhibited exceptional hydrophobicity with the water contact angle, reaching as high as 145.9° in the vertical direction (parallel to pore growth direction) and 136.3° in the horizontal direction (perpendicular to pore growth direction). Therefore, lightweight, mechanically flexible, thermally insulating, and hydrophobic PIFs were successfully prepared by the proposed approach, which demonstrate potential applications in the aerospace, transportation, microelectronics, and nuclear energy sectors, among others.
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PubMed
高影响因子
JOURNAL OF MEMBRANE SCIENCE
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2025
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IF 9
Jiayou Liao,Zhiyuan Wu,Zhe Meng,ChengYun Gao,Jinping Li,Yong Wang,Xianjie Meng,Jiwei Ma,Lijing Yuan,Xingzhong Cao,Xu Wu
A novel methodology was proposed to simultaneously enhance both permeability and selectivity of polyimide membranes through the synergistic regulation of interchain spacing, inter-chain interactions, and functional groups, collectively referred to as 'interchain microenvironment regulation'. Through reacting the -NH 2 group on the bulky diamines with the C-Br group on the polymer chains, we successfully linked the chains by bulky diamines. The results confirmed that the introduction of bulky groups inhibited chain stacking, increased d-spacing and free volume, resulting in enhanced permeability. Moreover, the CO 2 /CH 4 selectivity was significantly enhanced due to the synergistic effect between interchain interactions and the amino groups. In particular, the PI-Br-6%-NAPD membrane demonstrated a permeability coefficient 5 times greater than that of pure PI, reaching 311.71 Barrer. And its CO 2 /CH 4 selectivity was 3.87 times higher than pure PI, with a value of 74.88. It exceeded the 2008 Robeson upper bound for gas separation performance. In addition, enhanced interchain interactions endowed the membrane with good plasticization resistance, with a plasticization pressure of up to 450 psi. Membranes modified with other diamines also exhibited excellent gas separation performance. This study provided a feasible method for effectively regulating the interchain microenvironment to achieve high-performance gas separation.
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高影响因子
TRIBOLOGY INTERNATIONAL
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2025
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IF 6.9
Wangfei Shen,Qingzhe Zhang,Yingying Wang,Pu Zhang,Xiaoliang Zhang,Chunxia Wu,Cunxin Jia,Jingkang Liu,Xudong Xue,Yanming Wang
Two-dimensional lubricating fillers play a crucial role in strengthening the tribological performance of polymer coatings. In this study, MXene-PDA-Bi 6 O 7 (MXene/Bi 6 O 7 ) heterostructured composite nanofillers were prepared via a mussel-inspired chemical method. Polyimide (PI) composite coatings with varying MXene:Bi₆O₇ mass ratios were fabricated, and their microstructure, mechanical properties, and tribological performance were systematically characterized. The loading of Bi 6 O 7 nanoflowers onto the surface of PDA-modified MXene was achieved through in situ assembly, resulting in the formation of MXene/Bi 6 O 7 heterostructures. The experimental results demonstrated that the synergistic effect of MXene and Bi 6 O 7 significantly enhanced the properties of the PI composite coatings. Specifically, when the MXene-to-Bi₆O₇ mass ratio was 4:6, the PI composite coatings exhibited an 11.2 % reduction in friction coefficient and a 70.5 % decrease in wear rate compared with pure PI. Additionally, the tensile strength of the PI matrix was increased to 185.99 MPa. The MXene/Bi 6 O 7 heterostructure effectively reduced direct contact between the friction pairs by forming a dense transfer membrane, thereby maintaining stable lubrication performance under a broad range of conditions. The study elucidates the role of two-dimensional heterostructures in enhancing the interfacial mechanics and tribological properties of polymers, providing theoretical guidance and technical routes for the development of high-performance abrasion-resistant polymer coating materials.
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高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
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2020
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IF 16.683
Peng Kong,Hao Tan,Tingyu Lei,Jie Wang,Wenjun Yan,Ruiyi Wang,Eric R. Waclawik,Zhanfeng Zheng,Zhong Li
Conjugated polyimide (R-PI) containing triazine ring was synthesized by a modified thermal solid-state polymerization of the salt monomer. The structure of the as-prepared R-PI was characterized by FTIR, XPS, EPR, EA and solid-state 13 C NMR, which is rich in oxygen vacancies (OVs). The R-PI exhibits excellent catalytic performance for selective benzylamine oxidation reactions under visible light. Both experimental and theoretical calculation results indicated that the introduction of OVs could increase the level of electron delocalization of R-PI. R-PI possess more excitable electrons and a narrower band gap, which expands the absorption of long-wavelength light. The surface OVs also serve as excellent sites for molecular O 2 adsorption and activation. Chemisorbed O 2 spatially builds up a channel for the delivery of photoexcited electrons to O 2 , which effectively enhanced separation efficiency of photogenerated charge carriers. These results indicate that OVs-rich conjugated polyimides can be efficient visible light-responsive photocatalysts for green synthesis.
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高影响因子
JOURNAL OF MEMBRANE SCIENCE
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2019
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IF 7.015
Yanqing Wang,Zengqi Zhang,Lintao Dong,Yongcheng Jin
Polydopamine (PD) for polyimide (PI) separator coated-modification is investigated for lithium-sulfur (Li–S) battery. The asymmetric single-sided PI-PD separator is achieved by in-situ self-polymerization. According to testing, batteries obtain the best performances when PD loading is 0.8 mg cm −2 . Li–S battery with PD as a separator coating shows excellent electrochemical performance and high security. At 0.5C, battery with PI-PD obtains an initial discharge specific capacity of 1404.7 mAh g −1 , and it can be retained at 890.5 mAh g −1 after 100 cycles. A high specific capacity of 710 mAh g −1 is obtained at 5 C. The PD modified layer possesses abundant N, O-containing functional groups which has strong chemical adsorption with the polysulfides . At the same time, the PD layer formed on PI is a dense layer which can be used as a physical barrier. That means polysulfides can be effectively suppressed by both chemical adsorption and physical obstruct in batteries with PI-PD separators. Besides, the PI-PD separator improves the safety of battery because the thoroughly thermal runaway temperature of battery with PI-PD can be as high as 300 °C. Therefore, the introduction of PD as a material for coated separator is a promising method using in Li–S battery.
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高影响因子
AICHE JOURNAL
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2022
·Vol. 68
·期 8
·e17688
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IF 4.167
Xi Chen,Guining Chen,Guozhen Liu,Gongping Liu,Wanqin Jin
Mixed-matrix membranes (MMMs), judiciously combining processability of polymer and remarkable separation performance of nanofillers, have been extensive pursuits for molecular separation process. Permeability matching between filler and polymer is one of the necessary requisites to desirable mixed-matrix effect. Considering the superior molecular sieving effect of UTSA-280 metal-organic frameworks on C 2 H 4 and C 2 H 6 , here, we report two types of UTSA-280/6FDA-polyimide MMMs toward C 2 H 4 /C 2 H 6 separation. The molecular sieving effect of UTSA-280 endowed 6FDA-DAM:DABA(3:2) membrane with simultaneous improvements in C 2 H 4 permeability and C 2 H 4 /C 2 H 6 selectivity. Optimally, when the filler reached 21.80 wt%, C 2 H 4 permeability and C 2 H 4 /C 2 H 6 selectivity was increased to 6.49 Barrer (by 15%) and 4.94 (by 32%), respectively. On the contrary, UTSA-280/6FDA-DAM MMMs showed undesirable mixed-matrix effect that C 2 H 4 permeability decreased meanwhile C 2 H 4 /C 2 H 6 selectivity nearly kept at polymeric pristine membrane level. It was found that permeability matching between two phases was responsible to these opposite mixed-matrix effects. More specifically, UTSA-280 had a relatively low gas permeability so that it required a less permeable polymeric matrix like 6FDA-DAM:DABA(3:2) to exert its molecular sieving effect. Furthermore, the optimal-matching 6FDA-matrix in permeability with UTSA-280 fillers was predicted by theoretical model. This work not only reports improving C 2 H 4 /C 2 H 6 separation performance via mixed-matrix formulation, but also emphasizes the importance of permeability matching between polymer and filler to realize the mixed-matrix effect.
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高影响因子
IONICS
·
2021
·Vol. 27
·期 4
·1579-1588
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IF 2.817
Liu Zuyan,Yao Linxin,Hu Jiqing,Qiu Zhiming,Yan Yurong
A kind of fluorinated polyimide carrying sulfonyl groups (SFPI) as a novel binder is synthesized, which possesses excellent thermal stability, solubility, and mechanical properties. The cells with SFPI binder exhibit lower impedance and polarization compared with the cells adding the conventional PVDF binder. The electrochemical test results showed that the SFPI binder–based LiFePO 4 (LFP) electrode exhibits 134.1 mAh g −1 after 100 cycles and about 94.1% of the capacity is maintained. Especially, the overcharge safety of lithium-ion batteries during overcharge state is significantly improved by incorporating a SFPI binder.
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高影响因子
Journal of Materials Chemistry A
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2022
·Vol. 10
·期 20
·10950-10959
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IF 14.511
Xue-Jie Liu,Ming-Sheng Zheng,Gang Wang,Yi-Yi Zhang,Zhi-Min Dang,George Chen,Jun-Wei Zha
Polymer dielectrics have been widely used in electrical energy storage devices. However, the relatively low operating temperature hinders their applications in harsh environments. Herein, the molecular structure of polyimide (PI) is optimized by adjusting the reaction kinetics of polyamic acid, which improves the energy storage performance of PI at elevated temperature. The PI film with an optimal imidization degree achieves a simultaneous increase in dielectric permittivity (εr) and breakdown strength (Eb), resulting in a maximum discharged energy density (Ue) of 6.9 J cm−3 with a charge–discharge efficiency of 90.0% at room temperature and a high Ue of 3.9 J cm−3 at 150 °C. The introduced –COOH/–CN–OH– polar groups increase the εr through the enhancement of dipole polarization. Moreover, an appropriate number of –COOH/–CN–OH– groups as deep traps reduce the mobility of carriers, thereby increasing the Eb. Finite element simulation reveals that PI with an appropriate imidization degree exhibits suppressed space charge accumulation and improved electric field distortion. This method reduces the PI processing temperature, which effectively reduces the production energy consumption. For verifying the universality of the design strategy, two other PIs prepared from different monomers are also demonstrated to have simultaneous improvement in εr and Eb.Finally, this production process of only reducing the preparation temperature without adjusting the original commercial PI production equipment is crucial for the practical application of capacitor films in the future.
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高影响因子
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
·
2023
·
IF 4
Huijian Ye,Mengyao Ping,Wenxian Liu,Lixin Xu
Polymer films with tailored dielectric properties and large electrical displacement are required for applications in microelectronics due to the need for ultrahigh speed and low transmission delays. In this study, we developed a low- k polyimide (PI) nanocomposite incorporated with metal–organic framework hollow ZIF-8 (HZIF-8) nanocrystals to achieve a high energy storage capacity. The PI nanocomposite film was prepared by solution casting a mixture of HZIF-8/polyamide acid with thermal imidization. A dielectric constant of 2.26 was obtained at 100 Hz for the 5 wt% nanocomposite with a multi-stage pore architecture. Due to improved interfacial polarization, the 1 wt% nanocomposite had a high energy density of 12.2 J/cm 3 and a charge–discharge efficiency of 70% at 600 MV/m. The PI nanocomposite film exhibited dielectric reliability with inherent flexible performance, and it is expected to be a primary candidate for polymer dielectric applications in microelectronics.
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高影响因子
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