POLYMER INTERNATIONAL
·
2020
·Vol. 69
·期 5
·485-491
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IF 2.574
Guorong Qiu,Wenshi Ma,Li Wu
Polyimide microspheres were prepared via non-aqueous emulsion polymerization by using pyromellitic dianhydride (PMDA) as anhydride monomer and 2,2-bis(4-(4-aminophenoxy)phenyl)propane as amine monomer. The polyimide microspheres were well characterized by Fourier transform infrared spectroscopy, SEM and laser particle size analyzer. They were spherical in shape and monodisperse and their size was 31–33 μm. Polyimide mixtures formed by polyimide microspheres as fillers and polyimide composed of pyromellitic and dianhydride 4,4′-oxydianiline (ODA) as matrix were investigated with regard to thermal properties, dielectric properties and mechanical properties. With 10%–50% polyimide microspheres in the polyimide mixtures, the dielectric constants were 2.26–2.48 (1 MHz) and the loss tangents were 0.00663–0.00857 (1 MHz), which were both significantly lower than the values for ODA-PMDA polyimide. The decomposition temperature and glass transition temperature were above 440 and 290 °C. The polyimide mixtures possessed excellent thermal resistance. When the percentage of polyimide microsphere addition was 30%, the polyimide mixtures had the largest tensile strength (128.50 MPa) and elongation at break (9.01%). These results indicate that the polyimide microspheres were used as both low dielectric fillers and reinforcing fillers. © 2020 Society of Chemical Industry
研究领域:
材料科学
·
化学工程
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DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2021
·Vol. 138
·期 35
·50869
·
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.
研究领域:
材料科学
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复合材料工程
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DOI
高影响因子
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2021
·Vol. 222
·期 19
·2100197
·
IF 2.527
Yinfu Luo,Long Ni,Cheng Zhang,Liwei Yan,Huawei Zou,Shengtai Zhou,Mei Liang
Lightweight and excellent thermal stability hollow polyimide (PI) microspheres play an important role in high-end engineering applications such as aerospace, marine use among others. Herein, a simple approach is proposed to scalable fabrication of hollow PI microspheres with controllable sizes by powder foaming method combined with gradient heating strategy. The diameter of PI microspheres ranges from 295.5 to 1479.6 µm with a wall thickness of ≈7.78 µm. Interestingly, the diameter of PI microspheres exhibits a good correlation with the size of polyester ammonium salt (PEAS) particles. The hollow PI microspheres demonstrate excellent heat resistance with a bulk density ranging from 56.9 to 132.2 kg m –3 . Furthermore, PI microspheres could be readily converted into carbon microspheres without destroying their original integrity, which shows potential applications in preparing multifunctional composites. The proposed method is easily scalable which can be adopted to fabricate hollow PI microspheres at large quantities for industrial applications.
研究领域:
材料科学
·
航空航天工程
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DOI
高影响因子
CHROMATOGRAPHIA
·
2022
·Vol. 85
·期 10
·939-948
·
IF 2.213
Wu Yi,Zhong Dongdong,Qiu Qiankun,Yan Xiaohui,Wu Dapeng
In this work, nanoporous polyimide (PI) microspheres (NPMs) were prepared in bulk using the spray phase inversion technique. Due to the right size and shape, open nanopores with diameters of 10–70 nm, a large surface area of 52 m 2 g −1 , and abundant chemical extraction property, these NPMs were successfully used as solid phase extraction (SPE) sorbents. Combined with an ultra-performance liquid chromatography-fluorescence detector (NPM-SPE-UPLC-FLD), five fluoroquinolones (FQs) were quantified successfully in environmental water and food samples. After the NPMs with 50–75 μm diameters were collected by sieving, packed into an SPE cartridge, and conditioned by rinsing with acetonitrile and water, FQs in water samples were extracted and eluted with high recoveries between 75.5% and 112.3%. A breakthrough volume of 380 mL was obtained with only 20 mg of NPM sorbents. Under optimal conditions, the limits of detection for FQs in spiked purified water were 0.002–0.011 μg L −1 , and the linear range was more than three orders of magnitude (0.004–10 μg L −1 ) with good correlation coefficients of 0.9984–0.9996. The intra-batch relative standard deviations (RSDs) of the NPMs were 0.5%–9.8%, and the inter-batch RSDs were 1.6%–13.4%. Finally, the NPM-SPE-UPLC-FLD method was successfully applied to water, egg and milk samples. These results demonstrated that NPMs are promising candidates for SPE sorbents due to their convenient preparation and excellent performance in environmental water and food samples. Graphical abstract
研究领域:
分析化学
·
环境科学
·
食品科学
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DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Junfeng Yu,Nanxi Dong,Bingxue Liu,Guofeng Tian,Shengli Qi,Dezhen Wu
Polymer separators with high-temp dimensional stability is strongly demanded for high-safety lithium-ion batteries (LIBs). In this study, a novel polyimide (PI) microsphere coating slurry was prepared and then plated on Celgard polypropylene (PP) separator, producing PP@PI microsphere composite separator with excellent thermal stability, flame retardancy, high liquid retention capacity and high ionic conductivity by a simple blade-coating process. The results show that the thermal stability and liquid retention capacity of the PP@PI microsphere composite separator are significantly improved. Compared with the pure commercial PP separator which sharply shrank at 150 °C, the PI microsphere composite separator shows negligible shrinkage over 150 °C. The obtained PP@PI microsphere composite separators exhibited excellent thermal stability and fire-resistance properties. At the same time, the peel strength of composite separator reached 138.6 N·m −1 , with excellent adhesion. The surface density of PP@PI microsphere composite separator is 16.62 g·m −2 , which is lower than 30.22 g·m −2 of ceramic coated composite separator. Electrochemical characterizations indicate that the discharge capacity and capacity retention rate of the battery assembled with PP@PI microsphere composite separator are significantly higher than those assembled with the pure PP separator. The half-cell assembled with this composite separator shows a high capacity of 144.3 mAh·g −1 at 5C, which is much higher than the 117.8 mAh·g −1 of the commercial PP separator equipped battery. Moreover, the lithium-ion batteries assembled with the PP@PI microsphere composite separator show excellent cycle stability after 200 cycles at 1C. More importantly, the lithium-ion battery assembled with PP@PI microsphere composite separator has excellent safety at high temperature. These features demonstrate the potential of PP@PI microspheres composite membrane as high-security separator for LIBs.
研究领域:
材料科学
·
电化学
·
电池技术
·
高分子科学
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DOI
高影响因子
危险品化学品经营许可证（带存储）