Journal of Central South University
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2022
·Vol. 29
·期 6
·1761-1777
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IF 2.392
Wang Xian-peng,Hu Ai-ping,Chen Xiao-hua,Liu Ji-lei,Li Yan-hua,Li Chuan-yi,Wang Han,Tang Qun-li
The integration of electronic components and the popularity of flexible devices have come up with higher expectations for the heat dissipation capability and comprehensive mechanical performance of thermal management materials. In this work, after the modification of polyimide (PI) fibers through oxidation and amination, the obtained PDA@OPI fibers (polydopamine (PDA)-modified pre-oxidized PI fibers) with abundant amino groups were mixed into graphene oxide (GO) to form uniform GO-PDA@OPI composites. Followed by evaporation, carbonization, graphitization and mechanical compaction, the G-gPDA@OPI films with a stable three-dimensional (3D) long-range interconnected covalent structure were built. In particular, due to the rich covalent bonds between GO layers and PDI@OPI fibers, the enhanced synergistic graphitization promotes an ordered graphitized structure with less interlayer distance between adjacent graphene sheets in composite film. As a result, the optimized G-gPDA@OPI film displays an improved tensile strength of 78.5 MPa, tensile strain of 19.4% and thermal conductivity of 1028 W/(m·K). Simultaneously, it also shows superior flexibility and high resilience. This work provides an easily-controlled and relatively low-cost route for fabricating multifunctional graphene heat dissipation films.
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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2021
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IF 5.816
Jun Liu,Haorui Duan,Wenjie Xu,Jun Long,Wenheng Huang,Huan Luo,Jinchao Li,Yaping Zhang
A novel sulfonated multi-wall carbon nanotubes (s-MWCNTs) filler is synthesized by ring-opening reaction. And then, a series of branched sulfonated polyimide (bSPI)/s-MWCNTs composite membranes are also prepared for application in vanadium redox flow batteries (VRFBs). The optimized bSPI/s-MWCNTs-2% composite membrane has lower vanadium ion permeability (2.01 × 10 −7 cm 2 min −1 ) and higher proton selectivity (1.06 × 10 5 S min cm −3 ) compared to those of commercial Nafion 212 membrane. Moreover, the VRFB with bSPI/s-MWCNTs-2% composite membrane exhibits higher coulombic efficiencies ( CE s: 96.0–98.2%) and energy efficiencies ( EE s: 79.7–69.5%) than that with Nafion 212 membrane ( CE s: 86.5–92.5% and EE s: 78.5–67.6%) at 80–160 mA cm −2 . The VRFB with bSPI/s-MWCNTs-2% composite membrane has stable battery performance over 400 cycles at 100 mA cm −2 , whose EE value is in the top level among previously reported SPI-based composite membranes. The results show that the bSPI/s-MWCNTs-2% composite membrane has a great prospect in VRFB application.
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JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES
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2021
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IF 2.569
Yuejia Li,Wei Pan,Fenghua Zhang,Jinsong Leng
Shape memory polymers (SMPs) are smart materials that can be programmed to change shape under external stimuli, whereas the low storage modulus limit the application of them. Herein, carbon fabric (CF) reinforced shape memory polyimide composites (SMPICs) with high storage modulus were manufactured via hot pressing molding process. Firstly, we synthesized one kind of thermoplastic shape memory polyimide (SMPI) with glass transition temperature of 205°C by the two-step high-temperature solution polycondensation. In addition, the triamine was added in the SMPI system as a crosslinking agent to form the thermosetting SMPI with different crosslinking degree. In order to improve the storage modulus of SMPI, the CFs with three layers were embedded in thermosetting SMPI matrix. The storage modulus of the obtained SMPICs was as high as 26 GPa. The glass transition temperature and thermal decomposition temperature of SMPICs were up to 213°C and 505°C, respectively. Moreover, the shape fixation rate and recovery rate of SMPICs were both more than 94%. These SMPICs with high storage modulus is of great significance, proving more application potential in many fields such as aerospace.
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APPLIED CLAY SCIENCE
·
2021
·
IF 5.467
Fuxing Zhao,Jundong Zhu,Tangping Peng,Hao Liu,Shengzhuo Ge,Huasheng Xie,Le Xie,Chongwen Jiang
Excellent thermal insulating aerogels have broad application prospects in pipeline transportation, aerospace, construction and other fields. However, defects in thermal stability and mechanical are the main factors limiting their use to special environments. In this work, a novel polyimide composite aerogel is successfully synthesized through 3-Aminopropyltriethoxysilane (APTES) functionalized clay halloysite nanotubes (FHal) as inorganic enhancement phase and uniformly embedded in polyimide (PI) aerogels. Functionalization can increase the interfacial compatibility between clay inorganic phase and polyimide acid. The results indicated that FHal with high aspect ratio interacts with PI to form a three-dimensional network structure. The FHal/PI composite aerogels had low shrinkage (21.9%–30.79%), low bulk densities (65.285–71.464 mg/cm 3 ), low thermal conductivities (39.18–42.57 mW/(m·K)), high thermal stability (onset of decomposition above 520 °C) and excellent mechanical property (1.14 MPa, 2.62 times of pure PI aerogel). Therefore, FHal/PI composite aerogels can be used as a promising thermal management material for practical and complex insulation applications.
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JOURNAL OF APPLIED POLYMER SCIENCE
·
2021
·Vol. 138
·期 35
·50869
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IF 3.125
Xiaoqing Xu,Dechao Hu,Wenshi Ma
Achieving synergetic improvements of mechanical strength, toughness, and thermal stability of epoxy resin has been a crucial but very challenging issue. Herein, to explore a new solution for circumventing this issue, polyimide microspheres were successfully prepared through the inverse nonaqueous emulsion process, and the structure, size distribution and morphologies of polyimide (PI) microspheres were comprehensively investigated. Then the PI microspheres were incorporated in epoxy resin matrix to systematically investigate the mechanical and thermal properties of obtained epoxy/PI microspheres composites. It was found that the PI microspheres can not only enhance the mechanical strength of epoxy resin, but also significantly improve the toughness. Specially, the epoxy-based composites containing 3 wt% PI microspheres exhibit a 47% increase in tensile strength, while the G IC and Charpy impact strength increase by 106% and 200%, respectively. The toughing mechanism of epoxy/PI microspheres composites was discussed. Moreover, the PI microspheres can also endow the epoxy resin with excellent thermal stability and heat resistance. Thus, this work may open a new opportunity to synergistically enhance the mechanical and thermal properties of epoxy-based composites and may also give some valuable inspiration for the rational design of other high-performance thermosetting composites.
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CHEMICAL ENGINEERING JOURNAL
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2021
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IF 13.273
Qin Liu,Sheng Xu,Shu Xiong,Ming Yi,Yan Wang
Substrate modification of thin film composite (TFC) membranes by various crosslinkers is generally required for organic solvent nanofiltration (OSN) application, to enhance the membrane stability and solvent resistance, which however leads to the permeance decline. In this contribution, coordination-crosslinked polyimide substrate is developed for the first time, which is different with those covalently-crosslinked substrates, and achieves the enhanced solvent resistance, improved hydrophilicity and optimized porous microstructure simultaneously. The effects of the alkaline coagulation bath, subsequent ion exchange, and further solvent activation are investigated. The resultant TFC membrane breaks through the typical permeability-selectivity trade-off of OSN membranes successfully, exhibiting an astonishingly superior solvent permeance (1.5–2 times the highest data) (65.2 LMH/bar for methanol, 33.1 LMH/bar for ethanol and 59.1 LMH/bar for acetone) to previously reported polymeric-based TFC OSN membranes with a competitive solute rejection (>98% for Rose Bengal). This study is believed to provide a new orientation in the development of the desirable substrate for the high-performance OSN composite membrane and other separation applications.
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JOURNAL OF POWER SOURCES
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2020
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IF 8.247
Jun Wang,Hongyan Yao,Chunya Du,Shaowei Guan
Currently, organic electrode materials have shown promising prospects in lithium-ion batteries (LIBs). However, the practical application of organic electrode materials is severely hindered by the intrinsic low electrical conductivity and poor cycle stability. Herein, we present a novel polyimide (NBI-PI) which contains extended π-conjugated naphthalene ring and Schiff-base structure as an anode material . The NBI-PI has abundant active sites and crystallized nature. The organic anode based on NBI-PI for LIBs exhibit good reversible capacity of 627.8 mA h g −1 at 0.25 A g −1 after 200 cycles, and display reasonable rate performance of 217 mA h g −1 at 2 A g −1 . When the batteries are cycled at 2 A g −1 , capacity retention of 85.7% is attained after 1600 electrochemical cycles. This work demonstrates a facile and practical strategy to develop high-performance organic anode materials for lithium-ion batteries.
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JOURNAL OF MATERIALS SCIENCE
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2020
·Vol. 56
·期 5
·3900-3910
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IF 3.553
Liu Xufei,Qiu Shengqiang,Mei Peng,Zhang Qing,Yang Yingkui
Organic polyimides have received an ever-growing interest in lithium-ion batteries based on the reversible anion stabilization mechanism of redox-active carbonyl groups due to their high theoretical capacities, resource sustainability, and diverse chain structures. Herein, four linear polyimides with different chain structures were synthesized by a facile and green hydrothermal method. The chain structure-electrochemical performance relationship was explored by regulating active anhydride units and diamine linkers. The incorporation of flexible linkers between redox-active anhydrides results in the facile movement of polyimide chains and the formation of porous networks with abundant active sites. In contrast, rigid aromatic linkers with strong π – π conjugation tend to assemble into the orderly-stacked sheets, enabling the efficient electron transfer. When used as the battery cathode, 1,4,5,8-naphthalenetetracarboxylic dianhydride-based polyimide with a relatively flexible linker delivers the largest specific capacity. Such a polyimide also demonstrates the high cycling stability with a capacity retention up to 52% over 10000 cycles. In contrast, pyromellitic dianhydride-based polyimide with a benzene-enriched linker exhibits the lowest capacity and poor rate capability due to its densely-stacked sheets and limited exposure of active groups. The chain structure-dependent performance relationship of polyimides would offer new insights into the rational design of high-performance organic electrodes for the next-generation batteries.
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SEPARATION AND PURIFICATION TECHNOLOGY
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2021
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IF 7.312
Zhenggang Wang,Jianwei Yuan,Renhao Li,Haipeng Zhu,Jingui Duan,Yanan Guo,Gongping Liu,Wanqin Jin
Compared with traditional separation methods, membrane-based technology shows advantages in energy efficiency for natural gas purification. To overcome the performance trade-off of conventional polymeric membranes, in this study, ZIF-301 MOF was employed as novel filler to fabricate 6FDA-DAM polyimide mixed-matrix membranes (MMMs) for CO 2 /CH 4 separation. A solvent exchange approach was proposed to remove the high-boiling-point solvent used for fabricating the MMMs. The microstructures and physico-chemical properties of the ZIF-301 fillers and ZIF-301/6FDA-DAM MMMs were characterized by SEM, EDX, XRD, IR, TGA, DSC and high-pressure sorption isotherms. The CO 2 /CH 4 transport properties through the MMMs were evaluated by permeation measurement at various feed pressures and analyzed by solution-diffusion model. The results showed that the incorporation of ZIF-301 into 6FDA-DAM enhanced both the CO 2 permeability and CO 2 /CH 4 selectivity, attributing to the preferential CO 2 sorption and aperture molecular sieving effect of the ZIF-301 filler. The MMM with optimal ZIF-301 loading of 20 wt% exhibited CO 2 permeability of 891 barrer and CO 2 /CH 4 of 29.3 that surpassed the 2008 Robeson upper-bound, suggesting that ZIF-301 based membrane could be a potential candidate for natural gas purification.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2020
·
IF 3.573
Xuhua He,Yuechuan Wang
Multifunctional polymer composites with high thermal conductivity are beneficial as thermal management materials for advanced electronics and technologies because of their design flexibility. However, conventional polymer composites do not possess all of the desirable material properties. Here, using the binary fillers graphene oxide (GO) nanosheets and hexagonal boron nitride (BN) platelets, we fabricated flexible polyimide (PI) composite films with high thermal conductivity and excellent thermal and electrical insulating properties. For the resultant PI composite films, a maximum thermal conductivity of 11.203 W/(m K) was achieved at a low filler loading of 1 wt % GO and 20 wt % BN, approximately 50 times higher than that of neat PI films. Theoretical models demonstrated that this synergistic enhancement resulted from the interactions of the binary fillers. The PI composite films also showed improved thermal mechanical properties and thermal stability and retained electrical insulation, moderate dielectric permittivity, and low dielectric loss.
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MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2020
·Vol. 221
·期 12
·2000085
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IF 2.335
Zhigeng Chen,Sen Zhang,Qi Feng,Yancheng Wu,Shumei Liu,Jianqing Zhao
Both the formation of insoluble salt for aliphatic diamines and the poor reactivity for aliphatic dianhydrides result in semi-aromatic polyimide (SAPI) with low molecular weight and, thereby, in highly brittle SAPI films in nature. To solve the above problems, a cyclic-olefin copolymer synthesized from norbornene and maleic anhydride is used as the third monomer (crosslinking agent) to prepare the crosslinked SAPI (cSAPI) films. The relative viscosity of the precursor solution of cSAPI is increased with the loading of cyclic-olefin copolymer, giving rise to the improvement in mechanical and thermal properties of cSAPI films. The tensile modulus, tensile strength, and elongation at break of cSAPI film with 5 wt% cyclic-olefin copolymer are increased to 4.49 GPa, 137 MPa, and 14.9% from 3.57 GPa, 111 MPa, and 7.6%, respectively, compared to those of the baseline SAPI film. Meanwhile, the glass transition temperature of cSAPI films is increased to 282 from 270 °C of the SAPI film, which is advantageous to better meet the requirement for high-temperature manufacturing processes such as lead-free solder reflowing. In addition, all cSAPI films exhibit good optical transparency in the entire visible region.
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JOURNAL OF MEMBRANE SCIENCE
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2020
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IF 7.183
Chengyu Yang,Weixing Xu,Yang Nan,Yiguang Wang
Solvent-resistant nanofiltration (NF) membranes have numerous application prospects. In this study, a novel solvent-resistant nanofiltration membrane with a double layered polyamide structure was prepared for efficient desalination. The substrate was polyimide crosslinked with m -phenylenediamine (MPD), and the surface layer was polyamide prepared by typical interfacial polymerization. The crosslinking was confirmed by Fourier transform infrared spectroscopy . Investigation of the effects of different reaction conditions on membrane performance showed that the optimal reaction conditions were found to be: 5% aqueous MPD solution with crosslinking time of 10 min and piperazine concentration of 0.1% (m/v). The rejection rate for sodium sulfate and sodium chloride were 99.13% and 97.45%, respectively. The membrane morphologies were studied by scanning electron microscopy and atomic force microscopy . The membrane showed electronegativity in the pH range of 3.0–10.0 and its contact angle was 54.28°, indicating excellent hydrophilicity. After soaking in several solvents for a week, the membrane still had a high rejection rate of more than 90% for Na 2 SO 4 , demonstrating its excellent solvent resistance .
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