APPLIED SURFACE SCIENCE
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2022
·
IF 7.392
Xiong Yang,Guangyu Sun,Rundong Zhou,Kun Huang,Wendong Li,Chao Wang,Jiufeng Dong,Baipeng Song,Guanjun Zhang
Polymers with high surface electric insulation capability are greatly demanded in various electrical devices operating in vacuum ambient. Low secondary electron emission (SEE) is favorable to mitigate vacuum flashover by inhibiting the SEE avalanche across the surface. Although numerous approaches, esp. the surface modifications, promote the flashover strength of the insulator, a facile yet cost-effective modification strategy of a high-quality and scalable flexible insulator remains a formidable challenge. Herein, a facile ion-exchange technique is implemented to fabricate a nanoscale polyimide/chromic oxide (PI/Cr 2 O 3 ) nanocomposite coating comprising hundreds of organic/inorganic interfaces securely adhered to a flexible PI substrate, which features ultralow secondary electron emission yields (SEEY). The low emissivity is achieved by introducing weakly emissive Cr 2 O 3 nanoparticles as well as interfacial traps within the nanocomposite layer, which outperforms the existing and modified polymers. The PI/Cr 2 O 3 shows a remarkable increase in flashover strength while keeping sufficient mechanical durability. The proposed surface engineering strategy is convenient and scalable, bringing up new insight into industrial applications.
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PROGRESS IN ORGANIC COATINGS
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2022
·
IF 6.206
Feng Lang,Yu Xiang,Chunguang Xiao,Duxin Li
High-frequency trend of electrical equipment puts forward higher requirements on the dielectric properties of insulating materials, especially under corona ageing environment. Therefore, a facile and effective method for improved corona resistance is essential for the development of high-frequency power systems. In this article, 4,4′-Oxydiphthalic anhydride (ODPA) was chosen as the dianhydride while 4,4′-Diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenyl sulphide (SDA) as diamines. Consequently, thermally imidized ODPA-ODA-SDA copolyimides were synthesized, and the influence of ODPA and SDA on the dielectric properties was discussed. High-frequency corona ageing test was also conducted to investigate the relationship between dielectric properties and the corona resistance. From dielectric frequency spectra analysis, the ODPA-ODA-SDA copolyimide was considered to exhibit the best dielectric properties when SDA accounted for 30% mole fraction of diamine, the dielectric loss of which was 24.03% lower than that of ODPA-ODA at 20 kHz. Meanwhile, the better corona resistance property and mechanical properties were obtained, especially the corona ageing lifetime was 2.26 times higher than that of ODPA-ODA. To further improve the corona resistance property, a series of modified-PI/Al 2 O 3 nanocomposite films based on ODPA-ODA-SDA matrix were prepared by in-situ polymerization. When the content of Al 2 O 3 nanoparticles reached 12 wt%, the thermal stability was improved and the corona ageing lifetime was 6.14 times longer than that of ODPA-ODA. This experiment provides new ideas and directions for reducing mechanical and thermal performance losses as well as achieving high-efficiency corona resistance, which is expected to promote the development of advanced insulating films.
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HIGH PERFORMANCE POLYMERS
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2022
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IF 1.73
Rui Yang,Ming Yang Chen,Pei Li
Carbon molecular sieve (CMS) membranes have excellent gas separation property over conventional polymeric membranes and superior anti-swelling property. PMDA-ODA polyimide has high thermal stability and good mechanical property. It has been extensively adopted as the precursor of CMS membrane. However, due to the insoluble nature, PMDA-ODA CMS membranes are limited to configurations like dense symmetric films or composite membranes using porous inorganic or metal substrates. In this work, CMS hollow fiber composite membranes based on an asymmetric PMDA-ODA hollow fiber were successfully prepared for the first time. The neat PMDA-ODA hollow fiber membrane was crosslinked by polyethyleneimine to alleviate pore collapsing during carbonization and then dip-coated by a PMDA-ODA PAA solution to seal the surface defects. The PDMA-ODA CMS composite hollow fiber membranes showed gas permeances of 93.4 GPU, 19.6 GPU, 6.5 GPU, and 4.7 GPU for CO2, O2, N2, and CH4, respectively, with an ideal selectivity of 14.4, 3.0, and 19.8 for CO2/N2, O2/N2, and CO2/CH4 gas pairs, respectively. The attractive gas separation property shows a great potential for industrial application.
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MICROPOROUS AND MESOPOROUS MATERIALS
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2022
·
IF 5.876
Qingfu Ban,Yuanyuan Liu,Peiyan Liu,Yan Li,Yusheng Qin,Yaochen Zheng
Integrating organic multiple-carbonyl polymers and inorganic mesoporous metal oxides on highly conductive carbon nanotubes is a promising strategy to manufacture high-performance lithium-ion battery anodes; however, developing multicomponent nanocomposites with a hierarchical architecture still remain challenging. Herein, we design and produce hierarchically nanostructured carbon nanotube (CNT)/polyimide (PI)/mesoporous Fe 2 O 3 (meso-Fe 2 O 3 /PI/CNT) ternary nanocomposite materials via a sequential assembly and high-temperature dehydration strategy, aiming to fabricate flexible PI-supported meso-Fe 2 O 3 stacked on a conductive CNT supporting skeleton. By controlling the linear PI mainchain through the comonomer composition, different PI assemblies can grow on the surface of CNT to anchor meso-Fe 2 O 3 nanoparticles as well as alleviate the structural strain resulting from the volume expansion of meso-Fe 2 O 3 in its phase conversion reaction. Considering the porosity and cavity, the mesoporous Fe 2 O 3 architecture can not only buffer its volume expansion but also accommodate a large number of electrolytes to promote Li + transport. In addition, the hierarchical architecture endows the meso-Fe 2 O 3 /PI/CNT nanocomposite materials with a high structural stability during the electrochemical process. Benefiting from these structural advantages, Li-ion batteries assembled with meso-Fe 2 O 3 /PI-EDA/CNT electrodes deliver high capacities of 708.9, 608.2, and 454.5 mAh g −1 at 0.1, 0.3, and 0.5 A g −1 , respectively. Even at a high current density of 1 A g −1 , a discharge capacity of 95.6 mAh g −1 is still obtained after 3000 cycles. This work provides a promising route to integrate multiple-carbonyl polymers and mesoporous metal oxides with the aim of developing multicomponent organic-inorganic composite anode for Li-ion battery.
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Polymers
·
2022
·Vol. 14
·期 19
·4132
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IF 4.967
Yao Wang,Xiangfu Liu,Jiulin Shen,Jianqiao Zhao,Guoli Tu
A new series of colorless polyimides (CPIs) with outstanding thermal properties and mechanical properties were fabricated by the copolymerization of a novel dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2′-bistrifluoromethyl benzidine (TFDB). The novel dianhydride, 10-oxo-9-phenyl-9-(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetraacid dianhydride (3FPODA), possessed a rigid semi-alicyclic structure, –CF3and phenyl side groups, and an active carbonyl group. Benefitting from the special structure of 3FPODA, the glass transition temperatures (Tg) of the new CPIs improved from 330 °C to 377 °C, the coefficient of thermal expansion (CTE) decreased from 46 ppm/K to 24 ppm/K, and the tensile strength (TS), tensile modulus (TM), and elongation at break (EB) increased from 84 MPa to 136 MPa, 3.2 GPa to 4.4 GPa, and 2.94% to 4.13% with the increasing amount of 3FPODA, respectively. Moreover, the active carbonyl group of the 3FPODA could enhance the CPI’s adhesive properties. These results render the new dianhydride 3FPODA an ideal candidate monomer for the fabrication of high-performance CPIs.Keywords:colorless polyimide;new dianhydride;coefficient of thermal expansion;glass transition temperatures
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高影响因子
JOURNAL OF MEMBRANE SCIENCE
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2022
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IF 10.53
Can Wang,Zhili Cai,Wei Xie,Yang Jiao,Lu Liu,Lili Gong,Qi-Wei Zhang,Xiaohua Ma,Hongjun Zhang,Shuangjiang Luo
Thermally induced chemical crosslinking has attracted substantial attention for fabricating plasticization resistant membranes due to the facile structure tunability that enables the construction of robust and well-defined architecture for gas separation. In this study, we report a new series of dual thermally crosslinkable polyimides derived from 4,4′-diamino-2,2′-biphenyldicarboxylic acid (DCB) containing two carboxyl groups, and a systematic investigation of the thermal treatment above and below T g demonstrated the decarboxylation-induced crosslinking. The dual thermally crosslinked membranes were insoluble in common organic solvents and maintained excellent mechanical properties . Due to the evolution of CO 2 and collapse of chain segments during thermal treatment, the crosslinked membranes exhibited hierarchical microcavity size distribution featuring ultra-micropore size in the range of 2.0–6.0 Å and micropore size in the range of 6.5–10.0 Å. Gas transport properties of the crosslinked membranes were feasibly tuned through the chemical compositions and thermal treatment procedures. For instance, the CO 2 permeability of crosslinked 6FDA-DAM 0.7 -TFMB 0.1 -DCB 0.2 increased almost three-fold with only a slight decrease in CO 2 /CH 4 selectivity. The crosslinked membranes also demonstrated superior plasticization resistance with mixed-gas feed pressure up to 40 bar and excellent low-temperature gas separation performance at −30 °C, making them attractive for aggressive gas separations.
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Gels
·
2022
·Vol. 8
·期 5
·308
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IF 4.432
Zixuan Zheng,Guojie Liang,Li Li,Jing Liu,Xinbo Wang,Yi Sun,Kai Li
The weak inherent non-covalent interactions between carbon aerogel backbone nanoparticles obtained by the pyrolysis of conventional organic aerogel can lead to poor mechanical properties. When applied in the thermal protection system of a high-speed spacecraft, the preparation of carbon aerogel insulation materials with excellent formability and high mechanical strength still remains a huge challenge. This work reports an efficient approach for fabricating carbon foam-reinforced carbon aerogel composites by compounding the nanoporous polyimide aerogel into the microporous pre-carbonized phenolic resin-based carbon foam via vacuum impregnation, gelatinizing and co-carbonization. Benefiting from the co-shrinkage caused by co−carbonization, the thermal insulation capacity of the carbon aerogel and the formability of the pre−carbonized foam are efficiently utilized. The shrinkage, density and carbon yield of aerogels, pre-carbonized foams and the composites at different temperatures were measured to analyze the formation of the interfacial gap within the composite. The co-carbonization mechanism of the polyimide aerogels and phenolic resin-based pre-carbonized foams was analyzed through XPS, TG-MS, and FT-IR. Among the prepared samples, CF30-CPI-1000 °C with small interfacial gaps showed the lowest thermal conductivity, which was as low as 0.56 W/(m·K) at 1900 °C, and the corresponding compressive strength and elastic modulus were as high as 0.532 MPa and 9.091 MPa, respectively.Keywords:polyimide aerogel;carbon aerogel;thermal conductivity;shrinkage;co-carbonization mechanism
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JOURNAL OF MEMBRANE SCIENCE
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2022
·
IF 10.53
Yang Wang,Minhao Guo,Hui Fu,Zhenzhong Wu,Yizhe Zhang,Guojie Chao,Suli Chen,Longsheng Zhang,Tianxi Liu
Separators are of significance in the thermal safety and energy-storage performance of lithium-ion batteries (LIBs). Thermotolerant separators of electrospun polyimide (PI) fibers hold great promise as candidate to commercial polyolefin-based separators due to their high thermal and electrochemical stability. However, their applications in LIBs are limited by the undesirably large pore size (∼2 μm) that will induce dendrite growth and thermal runaway of batteries. Here, we demonstrate a facile and scalable strategy to prepare thermotolerant separators of cross-linked PI fibers (c-PI) with a narrowed pore size (0.78 μm) via a blended electrospinning of polyamic acid and polystyrene followed by a thermal imidization. The electrospun fibers in the c-PI separator are ribborn-like and feature adhesion structure between adjacent fibers, while no such structures are observed for PI separator obtained without adding polystyrene. In comparison with the PI separators, the c-PI separator exhibits higher porosity, better electrolyte adsorption and higher ionic conductivity . In Comparison to the batteries with PI and Celgard separators, the battery with c-PI separator shows greatly enhanced electrochemical performance with a high capacity of 100.1 mAh/g at 10 C after 1600 cycles. This work offers a feasible and effective route to develop advanced membranes of electrospun fibers for safe LIBs.
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MACROMOLECULAR RAPID COMMUNICATIONS
·
2022
·Vol. 44
·期 2
·2200568
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IF 5.006
Aftab Ahmad,Guanghui Liu,Shimo Cao,Xuepeng Liu,Jinpeng Luo,Li Han,Hui Tong,Ju Xu
The development of novel polymer dielectrics with enhanced dielectric performance is a great challenge for application of film capacitors in modern electronics and electrical systems. Herein, an innovative approach of chemical vapor deposition polymerization technology is proposed to prepare the all-organic sandwich structured parylene/polyimide/parylene (Py/PI/Py) composite films by employing poly(chloro-para-xylylene) (parylene C) as the outer layers and polyimide (PI) as the inner layer. The Py/PI/Py composites exhibit superior thermal resistance and outstanding mechanical properties. Moreover, thanks to the interfacial effect which contributes to reinforcing the dielectric response and the thickness effect which facilitates improving the breakdown strength, the dielectric performance of Py/PI/Py composites has been enhanced significantly. Accordingly, dielectric constant of 4.52–5.09, dissipation factor of 0.21–1.01%, and breakdown strength of 307–460 MV m −1 are achieved. Besides, notable energy storage performance is also obtained in Py/PI/Py composite dielectrics. Consequently, this novel application of chemical vapor deposition polymerization method in preparing all-organic multilayered polymer composite films with sandwich structure shows promising potential in film capacitor applications in harsh conditions.
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APPLIED SURFACE SCIENCE
·
2022
·
IF 7.392
Liang Zhou,Huimin Qi,Yang Lei,Jiaxin Yu,Baogang Guo,Ding Zhang
Copolymers of polyimide and polyuria with different fractions were synthesized. Furthermore, Ti 3 C 2 MXene two-dimensional material was obtained by etching Ti 3 AlC 2 with hydrofluoric acid. It was demonstrated that the copolymers displayed outstanding tribological performance than that of pure polymers and the as-synthesized Ti 3 C 2 MXene were endowed with outstanding dispersion in above copolymer. Importantly, when used as a solid lubricant additive at different temperatures, the two-dimensional material showed excellent friction reducing and antiwear properties. That is, blending even a small fraction of Ti 3 C 2 MXene into the copolymer dramatically reduced the friction and wear of the friction pair. SEM mappings and XPS analyses revealed that a continuous tribofilm consisting of a high fraction of tribo-chemical products and TiO 2 was established on the rubbed surfaces, which were significant in improving the lubrication performance at different temperatures.
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NANO
·
2022
·
IF 1.438
Peidong Liu,Xiaodan Hu,Xinjian Wu,Yining Zhong,Shihui Song,Shuquan Chang,Haiqian Zhang,Xiaohong Zhang
Polyimide (PI) is an important engineering material, but its poor thermal conductivity limits its application in the field of electronic packaging. In this work, we prepared boron nitride nanosheets (BNNSs) and boron nitride nanosheets/silver nanoparticles (BNNSs/AgNPs) hybrid fillers which combined successfully with the PI matrix by in - situ polymerization to produce high-thermal-conductivity PI composites. The results showed that when the filler addition was 20 wt.%, the composites had the best overall performance, and the thermal conductivities of the BNNSs/PI and BNNSs/AgNPs/PI composite films were 0.863 W ⋅ m − 1 ⋅ K − 1 and 1.175 W ⋅ m − 1 ⋅ K − 1 , respectively, which improved 506% and 726%, respectively, compared with pure PI. Furthermore, the volume resistivity of the composites is higher than 10 1 7 Ω ⋅ cm , indicating an excellent insulating property. At the same time, when used as the thermal interface material (TIM) for light-emitting diode (LED) chips, the composites have significantly improved heat dissipation effect and excellent mechanical properties at 75 ∘ C, which are expected to be widely used in the field of electronic packaging.
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Materials Today Physics
·
2021
·
IF 9.298
Zhouping Sun,Jiali Chen,Xichen Jia,Guoqing Wang,Bin Shen,Wenge Zheng
Though conductive polymer composite (CPC) foams have been investigated widely for electromagnetic interference (EMI) shielding owing to their low density and high EM absorption, fabricating high-performance CPC foams through a simple and easy-to-scale preparation process, as well as exploring new approach to achieve the shielding enhancement of CPC foams under mild conditions for meeting some special circumstances that needing higher shielding effectiveness (SE) in a short time, is still of great importance. In this work, multifunctional polyimide/carbon nanotube composite foams (PIF/CNT) were manufactured by the combination of effective chemical-foaming method and simple solution dip-coating approach. The resultant PIF/CNT with ultralow density exhibited the integration of excellent performances on absorbing-dominant EMI shielding with the extreme-temperature adaptability, flame retardancy , thermal insulation , infrared stealth and Joule-heating functions. On the other hand, the idea of humidifying-enhanced EMI shielding is proposed, and the EMI SE of wetted PIF/CNT samples can be massively improved due to the easy adsorption of strongly polar water molecules on the open-cell foam skeleton with hydrophilic poly (vinyl pyrrolidone). By the humidifying-drying cycles to enhance or restore the SE performance, our PIF/CNT material can be adjusted within a certain SE range to achieve intelligent electromagnetic response, providing another important guide for the design of novel intelligent EMI shields.
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