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polyimide Aerogel Fibers with Controllable Porous Microstructure for Super‑Thermal Insulation Under Extreme Environments

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Advanced Fiber Materials 2022年第5期4卷 1118-1128页

作者： Tiantian Xue Chenyu Zhu Xueling Feng Qamar Wali Wei Fan Tianxi Liu State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua University2999 North Renmin RoadShanghai 201620People’s Republic of China Key Laboratory of Synthetic and Biological Colloids Ministry of EducationSchool of Chemical and Material EngineeringJiangnan UniversityWuxi 214122People’s Republic of China School of Applied Sciences and Humanities National University of TechnologyIslamabad 42000Pakistan

Application of aerogel fibers in thermal insulating garments have sparked a substantial interest.However,achieving a high porosity and low thermal conductivity for aerogel fibers remain challenging,despite the innovative designs of porous struc-ture.Herein,we fabricated lightweight and super-thermal insulating polyimide(PI)aerogel fibers via freeze-spinning by using polyvinyl alcohol(PVA)as a pore regulator.The high affinity of PVA with water enables it to accelerate the ice crystal nucleation,adjust pore formation,and construct a controllable porous structure of PI aerogel fiber.The as-fabricated PI aerogel fiber has a considerable reduced pore size,high porosity(95.6%),improved flexibility and mechanical strength,and can be woven into fabrics.The PI aerogel fabric exhibits low thermal conductivity and excellent thermal insulation in a wide range of temperature(from-196 to 300℃).Furthermore,the PI aerogel fabrics can be easily functionalized to expand their applications,such as in intelligent temperature regulation and photothermal conversion.These results demonstrate that the aerogel fibers/fabric are promising materials for next-generation textile materials for personal thermal management.

关键词： polyimide Aerogel fiber Pore regulation Thermal insulation Thermal management

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Hierarchically Multifunctional polyimide Composite Films with Strongly Enhanced Thermal Conductivity

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Nano-Micro Letters 2022年第2期14卷 94-106页

作者： Yongqiang Guo Hua Qiu Kunpeng Ruan Yali Zhang Junwei Gu Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072ShaanxiPeople’s Republic of China

The development of lightweight and integration for electronics requires flexible films with high thermal conductivity and electromagnetic interference(EMI) shielding to overcome heat accumulation and electromagnetic radiation pollution.Herein,the hierarchical design and assembly strategy was adopted to fabricate hierarchically multifunctional polyimide composite films,with graphene oxide/expanded graphite(GO/EG) as the top thermally conductive and EMI shielding layer,Fe_(3)O_(4)/polyimide(Fe_(3)O_(4)/PI) as the middle EMI shielding enhancement layer and electrospun PI fibers as the substrate layer for mechanical improvement.PI composite films with 61.0 wt% of GO/EG and 23.8 wt% of Fe_(3)O_(4)/PI exhibits high in-plane thermal conductivity coefficient(95.40 W(m K)^(-1)),excellent EMI shielding effectiveness(34.0 dB),good tensile strength(93.6 MPa) and fast electric-heating response(5 s).The test in the central processing unit verifies PI composite films present broad application prospects in electronics fields.

关键词： EMI shielding Flexible films polyimide Thermal conductivity

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Porous and Ultra-Flexible Crosslinked MXene/polyimide Composites for Multifunctional Electromagnetic Interference Shielding

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Nano-Micro Letters 2022年第4期14卷 59-74页

作者： Zhi-Hui Zeng Na Wu Jing-Jiang Wei Yun-Fei Yang Ting-Ting Wu Bin Li Stefanie Beatrice Hauser Wei-Dong Yang Jiu-Rong Liu Shan-Yu Zhao Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of Education and School of Materials Science and EngineeringShandong UniversityJinan 250061People’s Republic of China Department of Chemistry and Applied Biosciences ETH ZurichCH-8093 ZurichSwitzerland Laboratory for Cellulose and Wood Materials Swiss Federal Laboratories for Materials Science and Technology(Empa)8600 DübendorfSwitzerland Laboratory for Building Energy Materials and Components Swiss Federal Laboratories for Materials Science and Technology(Empa)8600 DübendorfSwitzerland School of Aerospace Engineering and Applied Mechanics Tongji UniversityShanghai 200092People’s Republic of China

Lightweight,ultra-flexible,and robust crosslinked transition metal carbide(Ti3C2 MXene)coated polyimide(PI)(C-MXene@PI)porous composites are manufactured via a scalable dip-coating followed by chemical crosslinking approach.In addition to the hydrophobicity,anti-oxidation and extreme-temperature stability,efficient utilization of the intrinsic conductivity of MXene,the interfacial polarization between MXene and PI,and the micrometer-sized pores of the composite foams are achieved.Consequently,the composites show a satisfactory X-band electromagnetic interference(EMI)shielding effectiveness of 22.5 to 62.5 dB at a density of 28.7 to 48.7 mg cm−3,leading to an excellent surface-specific SE of 21,317 dB cm^(2)g^(−1).Moreover,the composite foams exhibit excellent electrothermal performance as flexible heaters in terms of a prominent,rapid reproducible,and stable electrothermal effect at low voltages and superior heat performance and more uniform heat distribution compared with the commercial heaters composed of alloy plates.Furthermore,the composite foams are well attached on a human body to check their electromechanical sensing performance,demonstrating the sensitive and reliable detection of human motions as wearable sensors.The excellent EMI shielding performance and multifunctionalities,along with the facile and easy-to-scalable manufacturing techniques,imply promising perspectives of the porous C-MXene@PI composites in next-generation flexible electronics,aerospace,and smart devices.

关键词： MXene polyimide Electromagnetic interference shielding Heater Sensor

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Highly Hydrolysis-Resistant polyimide Fibers Prepared by Thermal Crosslinking with Inherent Carboxyl Groups

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Chinese Journal of Polymer Science 2024年第2期42卷 247-255,I0010页

作者： Can-Can Zhang Jun-Long Yang Ya-Jiang Huang Guang-Xian Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials Engineering of ChinaSichuan UniversityChengdu610065China

Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chains. In this work, crosslinked polyimide fibers(CPI fibers) were produced by intrinsic carboxyl decarboxylation for the first time. The thermal stability of the polyimide fibers containing the intrinsic carboxyl groups(PIC fibers) was studied, and the temperature of the decarboxylation-crosslinking reaction was determined to be 450 ℃. The PIC fibers were hotdrawn to initiate thermal crosslinking of the carboxyl groups and molecular chain orientation at high temperature. The CPI fibers had high tensile strengths(0.72-1.46 GPa) and compressive strengths(401-604 MPa). The oriented macromolecules and chemically crosslinked structure improved the tightness of the molecular chains and endowed the CPI fibers with excellent hydrolytic resistance. The CPI-50 fiber did not dissolve in a 0.5 wt% NaOH solution during heating at 90 ℃ for 10 h, and the tensile strength retention reached 87% when treated in 0.5 wt% NaOH solutions at 90 ℃ for 1 h, providing a guarantee for its application in alkaline corrosive environments.

关键词： polyimide Carboxyl group Crosslinking Hydrolysis-resistance

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A one-for-all strategy of polyimide coating layer for resolving the comprehensive issues of phosphorus anode

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Journal of Energy Chemistry 2022年第7期31卷 276-282,I0008页

作者： Muyao Han Shaojie Zhang Yu Cao Chengyu Han Xu Li Yiming Zhang Zhanxu Yang Jie Sun Key Laboratory for Green Chemical Technology of Ministry of Education School of Chemical Engineering and TechnologyTianjin UniversityTianjin UniversityTianjin 300350China School of Petrochemical Engineering Liaoning Petrochemical UniversityFushun 113001LiaoningChina

Phosphorus is a promising anode with high capacity (2596 mAh g^(-1)and 6075~6924 mAh cm^(-3)),low lithium-ion diffusion barrier (0.08 e V),and appropriate lithiation potential (~0.7 V vs Li+/Li).However,it faces the problems of huge volume expansion (~300%),low electronic conductivity (10^(-14)~10^(2)S cm^(-1)),soluble intermediates (lithium polyphosphides,Li_(x)Ps),degradation in air,and low thermal stability.In this work,phosphorus/carbon nanotube composites were coated with a polyimide layer,which plays the roles of a buffer layer to relieve the volume expansion of phosphorus,an obstruct layer to confine LixPs,an inert layer to prevent the degradation of phosphorus in air,a heat resistant layer to improve the thermal stability of the anode.The resulting composites (P/CNT@PI) display high capacity retention of798.1 m Ah g^(-1)after 150 cycles at 1 A g^(-1),achieving 17 times as much as the control sample (P/CNT).

关键词： Phosphorus anode polyimide Lithium-ion batteries Surface coating

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polyimide separators for rechargeable batteries

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Journal of Energy Chemistry 2021年第7期30卷 170-197页

作者： Ziheng Lu Fan Sui Yue-E Miao Guohua Liu Cheng Li Wei Dong Jiang Cui Tianxi Liu Junxiong Wu Chunlei Yang Shenzhen Institutes of Advanced Technology Chinese Academy of SciencesShenzhen 518055GuangdongChina College of Materials Science and Engineering Donghua UniversityShanghai 201620China Department of Materials Science and Engineering Clemson UniversityClemsonSC 29634USA Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong KongChina

Separators are indispensable components of modern electrochemical energy storage devices such as lithium-ion batteries(LIBs).They perform the critical function of physically separating the electrodes to prevent short-circuits while permitting the ions to pass through.While conventional separators using polypropylene(PP) and polyethylene(PE) are prone to shrinkage and melting at relatively high temperatures(150℃ or above) causing short circuits and thermal runaway,separators made of thermally stable polyimides(PIs) are electrochemically stable and resistant to high temperatures,and possess good mechanical strength-making them a promising solution to the safety concerns of LIBs.In this review,the research progress on PI separators for use in LIBs is summarized with a special focus on molecular design and microstructural control.In view of the significant progress in advanced chemistries beyond LIBs,recent advances in PI-based membranes for applications in lithium-sulfur,lithium-metal,and solid-state batteries are also reviewed.Finally,practical issues are also discussed along with their prospects.

关键词： polyimide Lithium-ion batteries Separators Solid-state batteries Molecular design

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Porous Ti_(3)C_(2)T_(x) MXene nanosheets sandwiched between polyimide fiber mats for electromagnetic interference shielding

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Nano Research 2024年第3期17卷 2070-2078页

作者： Wenhao Liang Juntao Wu Shan Zhang Pei-Yan Zhao Yi Cong Yongqiang Guo Guang-Sheng Wang Key Laboratory of Bioinspired Smart Interfacial Science and Technology of Ministry of Education School of ChemistryBeihang UniversityBeijing 100191China

With the rapid development of wireless communication technology and electronic devices,the issue of electromagnetic interference(EMI)is becoming increasingly severe.Developing a new and flexible electromagnetic interference shielding material has become a challenging task.Here,a sandwich-structured EMI shielding composite film was prepared using electrospinning and vacuum filtration methods.In this process,a porous MXene was synthesized through a reaction with cobalt acetate and served as the intermediate layer in the composite film to shield electromagnetic waves.The electrospun polyimide(PI)fibers were used as the top and bottom layers of the composite film,which can protect the porous MXene from oxidation.This lightweight and flexible composite film integrates electromagnetic interference shielding and thermal insulation capabilities,showing excellent comprehensive performance.The composite film achieves an EMI shielding effectiveness of 48.8 dB in X-band(8.2–12.4 GHz),and absolute shielding effectiveness of the composite film reached a satisfying 4142.43(dB·cm^(2))/g.Owing to the design of a multi-layer porous structure,the density of the composite film is 0.65 g/cm3.Furthermore,the thermal conductivity of the film is 0.042 W/(m·K)due to the clamping of electrospun PI fibers,showing excellent thermal insulation performance.Additionally,the composite film exhibits excellent high and low-temperature resistance.In summary,this work provides a feasible strategy for preparing a lightweight polymer-based EMI shielding film.

关键词： porous MXene polyimide electromagnetic interference shielding thermal insulation

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Tribological behavior of lubricant-impregnated porous polyimide

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Friction 2024年第4期12卷 711-725页

作者： Jinbang LI Ningning ZHOU Janet SSWONG School of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms Beijing Institute of Control EngineeringBeijing 100029China Department of Mechanical Engineering Imperial College LondonLondon SW72AZUK

Porous materials impregnated with lubricants can be used in conditions where limited lubricant is desirable.In this work,three porous polyimides(PPI)with different densities were prepared.Polyalphaolefin(PAO)impregnated PPI(iPPI)discs were rubbed against steel and sapphire balls.In operando observations of the iPPI-sapphire contacts show that oil is released under an applied load,forming a meniscus around contacts.Cavitation at the outlet is created at high sliding speeds.The amount of released oil increases with increasing PPI porosity.Contact moduli,E*,estimated based on the actual contact size show that trapped oil in iPPIs contributes to load support.At higher speeds,tribological rehydration of the contact occurs in low density iPPI,with that E*rises with speed.For high density PPIs,high speeds give a constantly high E*which is limited by the viscoelastic properties of the PPI network and possibly the rate of oil exudation.Friction of iPPI-steel contacts is governed by the mechanical properties of the PPI,the flow of the lubricant,and the roughness of the PPI surfaces.For low-and medium-density(highly porous,high roughness)PPIs,large amount of oil is released,and lubrication is mainly via lubricant restricted in the contact in the pores and possibly tribological rehydration.For high density(low porosity)PPI,with lower roughness,hydrodynamic lubrication is achieved which gives the lowest friction.Our results show that polymeric porous materials for effective lubrication require the optimization of its surface roughness,stiffness,oil flow,and oil retentions.

关键词： polyimide porous material friction mechanism polymer limited lubrication

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Superlubricity by polyimide-induced alignment

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Friction 2023年第9期11卷 1690-1707页

作者： Xinlei GAO Hao CHEN Hong YAN Chengrui HUANG Li WU Tingting WANG School of Materials Science and Engineering Hubei UniversityWuhan 430062China School of Chemical and Environmental Engineering Wuhan Polytechnic UniversityWuhan 430023China State Key Laboratory of Chemical Resource Engineering College of ChemistryBeijing University of Chemical TechnologyBeijing 100029China School of Chemistry and Environmental Engineering Wuhan Institute of TechnologyWuhan 430074China

We have investigated the lubrication alignment behavior of point–plane contact and plane–plane contact between the GCr15 steel and polyimide(PI)friction pair using nematic liquid crystals(LCs)as the lubricant.In this system,rubbing orients the macromolecular PI molecules,and the oriented PI molecules induce alignment of the LC molecules in contact with or close to the oriented PI molecules.The LC molecules are aligned in the wear scar grooves of the PI film,and alignment extends to the GCr15-steel counterpart.Alignment of the LC molecules is correlated with the strong interaction force between the PI and LC molecules,the stable coordination structure of the LCs and GCr15 steel,and the weak interaction between the LC molecules.We performed simulations of the pretilt angle of PI and LCs and discussed the relationship between the pretilt angle and the friction properties.Owing to the small pretilt angle between PI and the LCs,the LC molecules orient almost parallel to the PI material,which is beneficial for superlubricity of this type of friction system.

关键词： superlubricity polyimide liquid crystal alignment

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Thermally Conductive polyimide/Boron Nitride Composite Films with Improved Interfacial Compatibility Based on Modified Fillers by polyimide Brushes

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Chinese Journal of Polymer Science 2023年第12期41卷 1921-1936,I0009页

作者： Meng-Yan Gao Lei Zhai Song Mo Yan Jia Yi Liu Min-Hui He Lin Fan Key Laboratory of Science and Technology on High-tech Polymer Materials Institute of ChemistryChinese Academy of SciencesBeijing 100190China School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049China

polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields.As one of the key technical challenges to be solved,interfacial compatibility between filler and matrix plays an important role for composite film.Herein,boron nitride was modified by grafting polyimide brushes via a twostep method,and a series of thermally conductive polyimide/boron nitride composite films were prepared.Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced,resulting in a significant reduction in defects and interfacial thermal resistance.The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface.As a result,composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler.Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%.The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m^(-1)·K^(-1),respectively.In addition,thermal and dielectric properties of composite films were also enhanced to some extent.The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties.

关键词： polyimide Composite film Boron nitride Thermal conductivity Interfacial compatibility

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