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Breaking Through Bottlenecks for Thermally Conductive Polymer Composites:A Perspective for Intrinsic Thermal Conductivity,Interfacial Thermal Resistance and Theoretics

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Nano-Micro Letters 2021年第7期13卷 118-126页

作者： junwei gu Kunpeng Ruan MOE Key Laboratory of Material Physics and Chemistry Under Extraordinary Conditions Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’anShaanxi 710072P.R.China

Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their ***,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer *** at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental ***,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.

关键词： Thermally conductive polymer composites Intrinsic thermal conductivity Interfacial thermal resistance Thermal conduction models Thermal conduction mechanisms

Random copolymer membrane coated PBO fibers with significantly improved interfacial adhesion for PBO fibers/cyanate ester composites

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Chinese Journal of Aeronautics 2021年第2期34卷 659-668页

作者： Lin TANG Junliang ZHANG junwei gu Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Poly technical UniversityXi'an 710072China

Poly(p-phenylene-2,6-benzobisoxazole)(PBO) fibers possess excellent dielectric, mechanical properties and heat resistance. However, the surface of PBO fibers is smooth and highly chemical inert, resulting in poor interfacial compatibility to polymer matrix, which severely limits its wider application in high-performance fiber-reinforced resin matrix composites. In this work, random copolymers(P(S-co-BCB-co-MMA)) containing benzocyclobutene in the side-chain were synthesized by reversible addition-fragmentation chain transfer(RAFT) polymerization, which were then utilized to form dense random copolymer membrane on the surface of PBO fibers by thermally cross-linking at 250 °C(PBO@P fibers). Four kinds of synthesized P(S-co-BCB-co-MMA) with different number-average molar mass(Mn) were well controlled and possessed narrow *** the Mnwas 32300, the surface roughness of PBO@P fibers was increased from 11 nm(PBO fibers) to 39 nm. In addition, PBO@P fibers presented the optimal interfacial compatibility with bisphenol A cyanate(BADCy) resins. And the single fiber pull-out strength of PBO@P fibers/BADCy micro-composites was 4.5 MPa, increasing by 45.2% in comparison with that of PBO fibers/BADCy micro-composites(3.1 MPa). Meantime, PBO@P fibers still retained excellent tensile strength(about 5.1 GPa). Overall, this work illustrates a simple and efficient surface functionalization method, which would provide a strong theoretical basis and technical support for controlling the surface structure & chemistry of inert substrates.

关键词： RAFT polymerization Membrane PBO fibers Bisphenol A cyanate(BADCy)resins Interfacial adhesion

Janus(BNNS/ANF)-(AgNWs/ANF)thermal conductivity composite films with superior electromagnetic interference shielding and Joule heating performances

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Nano Research 2022年第5期15卷 4747-4755页

作者： Yixin Han Kunpeng Ruan junwei gu Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072China

Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial intelligence and wearable *** this work,silver nanowires(AgNWs)are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent,and boron nitride(BN)is performed to prepare BN nanosheets(BNNS)with the help of isopropyl alcohol and ultrasonication-assisted peeling method,which are compounded with aramid nanofibers(ANF)prepared by chemical dissociation,respectively,and the(BNNS/ANF)-(AgNWs/ANF)thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the"vacuum-assisted filtration and hot-pressing"***(BNNS/ANF)-(AgNWs/ANF)composite films exhibit"one side insulating,one side conducting"performance,the surface resistivity of the BNNS/ANF surface is 4.7×10^(13) Ω,while the conductivity of the AgNWs/ANF surface is 5,275 S/*** Janus(BNNS/ANF)-(AgNWs/ANF)composite film with thickness of 95 pm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K)and superior electromagnetic interference shielding effectiveness of 70 *** obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 *** also has good temperature-voltage response characteristics(high Joule heating temperature at low supply voltage(5 V,215.0℃),fast response time(10 s)),excellent electrical stability and reliability(stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).

关键词： thermal conductivity composite film Janus structure aramid nanofibers electromagnetic interference shielding performance Joule heating

Enhanced Thermal Conductivities of Liquid Crystal Polyesters from Controlled Structure of Molecular Chains by Introducing Different Dicarboxylic Acid Monomers

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Research 2022年第4期2022卷 507-517页

作者： Xiao Zhong Kunpeng Ruan junwei gu Research Development Institute of Northwestern Polytechnical University ShenzhenGuangdong 518057China Shanxi Key Laboratory of Macromolecular SCcience and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi 710072China

Enhancing thermal conductivity coefficient (λ) of liquid crystal polyesters would further widen their application in electronics and electricals. In this work, a kind of biphenyl-based dihydroxy monomer is synthesized using 4, 4’-biphenyl (BP) and triethylene glycol (TEG) as raw material, which further reacts with three different dicarboxylic acids (succinic acid, p-phenylenediacetic acid, and terephthalic acid, respectively) by melt polycondensation to prepare intrinsically highly thermally conductive poly 4’, 4”’-[1, 2-ethanediyl-bis(oxy-2, 1-ethanediyloxy)]-bis(p-hydroxybiphenyl) succinate (PEOS), poly 4’, 4”’-[1, 2-ethanediyl-bis(oxy-2, 1-ethanediyloxy)]-bis(p-hydroxybiphenyl) p-phenyldiacetate (PEOP) and poly 4’, 4”’-[1, 2-ethanediyl-bis(oxy-2, 1-ethanediyloxy)]-bis(p-hydroxybiphenyl) terephthalate (PEOT), collectively called biphenyl-based liquid crystal polyesters (B-LCPE). The results show that B-LCPE possess the desired molecular structure, exhibit smectic phase in liquid crystal range and semicrystalline polymers at room temperature, and possess excellent intrinsic thermal conductivities, thermal stabilities, and mechanical properties. λ of PEOT is 0.51 W/(m·K), significantly exceeds that of polyethylene terephthalate (0.15 W/(m·K)) which has similar molecular structure with PEOT, and also higher than that of PEOS (0.32 W/(m·K)) and PEOP (0.38 W/(m·K)). The corresponding heat resistance index (THRI), elasticity modulus, and hardness of PEOT are 174.6℃, 3.6 GPa, and 154.5 MPa, respectively, and also higher than those of PEOS (162.2℃, 1.8 GPa, and 83.4 MPa) and PEOP (171.8℃, 2.3 GPa, and 149.6 MPa).

关键词： properties ethane polyester

Multifunctional Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/polyimide)composite films with Janus structure for outstanding electromagnetic interference shielding and superior visual thermal management

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Nano Research 2022年第6期15卷 5601-5609页

作者： Yali Zhang Zhonglei Ma Kunpeng Ruan junwei gu Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072China

Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films have important application values in the fields of 5G communication technology,wearable electronic devices and artificial *** this work,Fe_(3)O_(4)/polyamic acid(PAA)nanofiber films are prepared by in-situ polymerization and electrospinning technology,and Ti_(3)C_(2)T_(x)nanosheets are deposited on the surface of the Fe_(3)O_(4)/PAA nanofiber films via vacuum-assisted ***,Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/polyimide(PI))composite films are obtained by thermal *** two sides of the Janus films exhibit completely different *** Fe_(3)O_(4)/PI side has excellent hydrophobicity and insulation property,and the Ti_(3)C_(2)T_(x)side has hydrophilicity and terrific *** the mass fraction of Ti_(3)C_(2)T_(x)is 80 wt.%,the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite film has excellent EMI shielding performances and mechanical properties,with EMI shielding effectiveness,tensile strength and Young’s modulus reaching 66 dB,114.5 MPa and 5.8 GPa,*** the same time,electromagnetic waves show different absorption shielding effectiveness(SEA)when incident from two sides of the Janus *** the electromagnetic waves are incident from the Fe_(3)O_(4)/PI side,the SEA of the Janus film is 58 dB,much higher than that when the electromagnetic waves are incident from the Ti_(3)C_(2)T_(x)side(39 dB).In addition,the Ti_(3)C_(2)T_(x)side of the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite films also has excellent electrothermal and photothermal conversion *** the applied voltage is 4 V,the stable surface temperature reaches 108°C;when it is irradiated by simulated sunlight with power density of 200 mW/cm2,the stable surface temperature reaches 95℃.

关键词： Janus structure Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite films electromagnetic interference shielding electrothermal conversion photothermal conversion

Flexible Ti_(3)C_(2)T_(x)/(Aramid Nanofiber/PVA)Composite Films for Superior Eectromagnetic Interference Shielding

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Research 2022年第2期2022卷 213-224页

作者： Yali Zhang Zhonglei Ma Kunpeng Ruan junwei gu Shanxi Key Laboratory of Macromolecular Science and Tefhnology School of Chemistry and Chemical EngineringNorthwestern Polytechmical UniversityXi'anShaanxi 710072China

Multifunctional electromagnetic interference(EMI)shielding materials would solve electromagnetic radiation and pollution problemsfrom ***,the directionalfreezedryingtechnology isutilizedtoprepare the aramid nanofber/polyvinyl alcohol aerogel with a directionally porous structure(D-ANF/PVA),and the Ti_(3)C_(2)T_(x)dispersion is fully immersed into the D-ANF/PVA aerogel via ultrasonication and vacuum-assisted ***_(3)C_(2)T_(x)/(ANF/PVA)EMI shielding composite films with directionally ordered structure(D-Ti_(3)C_(2)T_(x)/(ANF/PVA)are then prepared by freeze-drying and hot *** directionally porous structure enables the highly conductive TiCnanosheets to be wrapped on the directionally porous D-ANF/PVA framework in order arrangement and overlapped with each *** the hot pressing process effectively reduces the layer spacing between the stacked wavy D-ANF/PVA,to form a large number of TiCT T_(3)C_(2)T_(x)continuous conductive paths,which significantly improves the conductivity of the D-Ti_(3)C_(2)T_(x)/(ANF/PVA)EMI shielding composite film,When the amount of Ti_(3)C_(2)T_(x)is 80 wt%,the EMI shielding efectiveness(EMil SE)and specifc SE(SSE/t)of D-Ti_(3)C_(2)T_(x)/(ANF/PVA)EMI shielding composite film achieve 70 dB and 13790 dB-cmg(thickness and density of 120μm and 0.423g·cm^(-3))。far superior to random-structured T_(3)C_(2)T_(x)/(ANF/PVA)(R-TJCTM(ANF/PVA))composite film(46 dB and 9062 dBcm·g^(-3),respectively)via blending-freeze-drying followed by hot pressing ***,the D-TiCTJMANF/PVA)EMII shielding composite flm possesses excellent flexibility and foldability.

关键词： composite directional film

Intrinsic high thermal conductive liquid crystal epoxy film simultaneously combining with excellent intrinsic self-healing performance

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Journal of Materials Science & Technology 2021年第9期68卷 209-215页

作者： Xutong Yang Xiao Zhong Junliang Zhang junwei gu Research&Development JnsMute of Northwestern Polytechnical University in Shenzhen Guangdong518057China Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072China School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang471023China

One kind of side chain liquid crystal epoxy(S-LCE) based on biphenyl mesomorphic unit is synthesized from 2,2-bis(hydroxymethyl)propionic acid,4-phenyl phenol,and *** the intrinsic thermal conductive liquid crystal epoxy film(LCEF) simultaneously combining with intrinsic self-healing performance is then prepared via thiol-epoxide nucleophilic ring-opening reaction and coating method.1 H NMR and FTIR show that S-LCE and LCEF have been successfully prepared.S-LCE presents nematic liquid crystal from room temperature to 160℃.LCEF maintains nematic liquid crystal performance and shows highly intrinsic thermal conductivity & excellent self-healing *** conductivity coefficient(λ)values in vertical direction(λ⊥)and parallel direction(λ‖)of LCEF are 0.33 and 1.25 W/mK,re spectively,much higher than that of general bisphenol A epoxy resin(E-51,λ⊥ of 0.19 W/mK and λ‖ of0.65 W/mK).Tensile strength of LCEF is 10.6 MPa,which can maintain at 90.6 % and 61.3 % after one and four cycles of self-healing behavior,*** addition,LCEF presents a wide service temperature range(-9.8-251℃) and good thermal stability(THRI of 148.5℃).Simultaneously,LCEF has good transparency,flexibility,and tailorability,expected to be utilized in the fields of flexible electronic devices and intelligent structures.

关键词： Liquid crystal epoxy Self-healing performance Intrinsic thermal conductivity Thermal stability

Structural Design Strategies of Polymer Matrix Composites for Electromagnetic Interference Shielding:A Review

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Nano-Micro Letters 2021年第11期13卷 322-350页

作者： Chaobo Liang Zhoujie gu Yali Zhang Zhonglei Ma Hua Qiu junwei gu Key Laboratory of Functional Nanocomposites of Shanxi Province College of Materials Science and EngineeringNorth University of ChinaTaiyuan 030051China Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXian 710072China Research and Development Center Guangdong Suqun New Materials Co.LtdDongguan 523000China

With the widespread application of electronic communication technology,the resulting electromagnetic radiation pollution has been significantly *** matrix electromagnetic interference(EMI)shielding materials have disadvantages such as high density,easy corrosion,difficult processing and high price,*** matrix EMI shielding composites possess light weight,corrosion resistance and easy ***,the current polymer matrix composites present relatively low electrical conductivity and poor EMI shielding *** review firstly discusses the key concept,loss mechanism and test method of EMI *** the current development status of EMI shielding materials is summarized,and the research progress of polymer matrix EMI shielding composites with different structures is illustrated,especially for their preparation methods and ***,the corresponding key scientific and technical problems are proposed,and their development trend is also prospected.

关键词： Polymer matrix composites Electromagnetic interference shielding Structural design

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 ***,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 *** 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