Pre-polymerized vinyl trimethoxy silane(PVTMS)@MWCNT nano-aerogel system was constructed via radical polymerization,sol-gel transition and supercritical CO_(2)drying.The fabricated organic-inorganic hybrid PVTMS@MWCNT...Pre-polymerized vinyl trimethoxy silane(PVTMS)@MWCNT nano-aerogel system was constructed via radical polymerization,sol-gel transition and supercritical CO_(2)drying.The fabricated organic-inorganic hybrid PVTMS@MWCNT aerogel structure shows nano-pore size(30-40 nm),high specific surface area(559 m^(2)g^(−1)),high void fraction(91.7%)and enhanced mechanical property:(1)the nano-pore size is beneficial for efficiently blocking thermal conduction and thermal convection via Knudsen effect(beneficial for infrared(IR)stealth);(2)the heterogeneous interface was beneficial for IR reflection(beneficial for IR stealth)and MWCNT polarization loss(beneficial for electromagnetic wave(EMW)attenuation);(3)the high void fraction was beneficial for enhancing thermal insulation(beneficial for IR stealth)and EMW impedance match(beneficial for EMW attenuation).Guided by the above theoretical design strategy,PVTMS@MWCNT nano-aerogel shows superior EMW absorption property(cover all Ku-band)and thermal IR stealth property(ΔT reached 60.7℃).Followed by a facial combination of the above nano-aerogel with graphene film of high electrical conductivity,an extremely high electromagnetic interference shielding material(66.5 dB,2.06 mm thickness)with superior absorption performance of an average absorption-to-reflection(A/R)coefficient ratio of 25.4 and a low reflection bandwidth of 4.1 GHz(A/R ratio more than 10)was experimentally obtained in this work.展开更多
The surface chemistry of filler is closely related to the structure and morphology of nanocomposite foams.Changing the property of filler is widely used to control the cell structures and functionalize the composite f...The surface chemistry of filler is closely related to the structure and morphology of nanocomposite foams.Changing the property of filler is widely used to control the cell structures and functionalize the composite foams.Surface-functionalized graphene oxide（GO-ODA） was prepared by grafting octadecylamine（ODA） on the surface of graphene oxide（GO） to make the filler disperse better in the nanocomposites and have a strong interfacial interaction with polymer matrix.Poly（methyl methacrylate）（PMMA）/GO-ODA nanocomposite foams were obtained by solution blending and foamed using supercritical carbon dioxide（scCO2）.Compared to neat PMMA and PMMA/GO samples,the PMMA/GO-ODA nanocomposite foams showed improved cell structures with smaller size,higher cell density and more homogeneous distribution,which should be attributed to the heterogeneous nucleation caused by well-dispersed GO-ODA nanosheets.This work not only improved the compatibility and interfacial interaction of GO with polymer matrix but also indicated that the modified GO sheets can act as ideal filler to control the cell density,size and size distribution efficiently.展开更多
The electrical conductivity of conductive polymer composites(CPCs)with a classical double percolated structure is highly connected to the phase morphology.However,lots of conductive fillers,which are added to guarante...The electrical conductivity of conductive polymer composites(CPCs)with a classical double percolated structure is highly connected to the phase morphology.However,lots of conductive fillers,which are added to guarantee CPCs’electrical conductivity,caused increased viscosity and limited phase coarsening in traditional atmosphere annealing.Herein,a novel processing method of supercritical carbon dioxide(scCO_(2)),assisted phase coarsening for polylactide acid(PLA)/polystyrene(PS)/multi-wall carbon nanotube(MWCNT)composites was explored.It was first proved that obviously coarsened conductive network of double percolation after scCO_(2) annealing was achieved,which benefited from CO_(2) plasticized polymer chains and thus decreased viscosity.Therefore,the electrical properties and electromagnetic interference(EMI)shielding performance of the composites were significantly improved.The percolation threshold of PLA/PS/MWCNT composites decreased from 0.31 wt.%to 0.16 wt.%,and EMI shielding effectiveness increased from 32.8 to 37.4 dB at 5 wt.%MWCNT loading.This work provides a simple,green,and effective way of post-processing to tailor the phase structure via varying conditions of annealing medium such as temperature,CO_(2) pressure,and time,and gains CPCs with improved electrical conductivity and EMI shielding performance.展开更多
基金the National Natural Science Foundation(No.52073187)NSAF Foundation(No.U2230202)for their financial support of this project+3 种基金National Natural Science Foundation(No.51721091)Programme of Introducing Talents of Discipline to Universities(No.B13040)State Key Laboratory of Polymer Materials Engineering(No.sklpme2022-2-03)support of China Scholarship Council
文摘Pre-polymerized vinyl trimethoxy silane(PVTMS)@MWCNT nano-aerogel system was constructed via radical polymerization,sol-gel transition and supercritical CO_(2)drying.The fabricated organic-inorganic hybrid PVTMS@MWCNT aerogel structure shows nano-pore size(30-40 nm),high specific surface area(559 m^(2)g^(−1)),high void fraction(91.7%)and enhanced mechanical property:(1)the nano-pore size is beneficial for efficiently blocking thermal conduction and thermal convection via Knudsen effect(beneficial for infrared(IR)stealth);(2)the heterogeneous interface was beneficial for IR reflection(beneficial for IR stealth)and MWCNT polarization loss(beneficial for electromagnetic wave(EMW)attenuation);(3)the high void fraction was beneficial for enhancing thermal insulation(beneficial for IR stealth)and EMW impedance match(beneficial for EMW attenuation).Guided by the above theoretical design strategy,PVTMS@MWCNT nano-aerogel shows superior EMW absorption property(cover all Ku-band)and thermal IR stealth property(ΔT reached 60.7℃).Followed by a facial combination of the above nano-aerogel with graphene film of high electrical conductivity,an extremely high electromagnetic interference shielding material(66.5 dB,2.06 mm thickness)with superior absorption performance of an average absorption-to-reflection(A/R)coefficient ratio of 25.4 and a low reflection bandwidth of 4.1 GHz(A/R ratio more than 10)was experimentally obtained in this work.
基金supported by the National Natural Science Foundation of China(No.51373103 and No.51421061)the Science and Technology Department of Sichuan Province(No.2015HH0026)
文摘The surface chemistry of filler is closely related to the structure and morphology of nanocomposite foams.Changing the property of filler is widely used to control the cell structures and functionalize the composite foams.Surface-functionalized graphene oxide（GO-ODA） was prepared by grafting octadecylamine（ODA） on the surface of graphene oxide（GO） to make the filler disperse better in the nanocomposites and have a strong interfacial interaction with polymer matrix.Poly（methyl methacrylate）（PMMA）/GO-ODA nanocomposite foams were obtained by solution blending and foamed using supercritical carbon dioxide（scCO2）.Compared to neat PMMA and PMMA/GO samples,the PMMA/GO-ODA nanocomposite foams showed improved cell structures with smaller size,higher cell density and more homogeneous distribution,which should be attributed to the heterogeneous nucleation caused by well-dispersed GO-ODA nanosheets.This work not only improved the compatibility and interfacial interaction of GO with polymer matrix but also indicated that the modified GO sheets can act as ideal filler to control the cell density,size and size distribution efficiently.
基金The authors acknowledge the financial support of the National Natural Science Foundation of China(No.52173039).
文摘The electrical conductivity of conductive polymer composites(CPCs)with a classical double percolated structure is highly connected to the phase morphology.However,lots of conductive fillers,which are added to guarantee CPCs’electrical conductivity,caused increased viscosity and limited phase coarsening in traditional atmosphere annealing.Herein,a novel processing method of supercritical carbon dioxide(scCO_(2)),assisted phase coarsening for polylactide acid(PLA)/polystyrene(PS)/multi-wall carbon nanotube(MWCNT)composites was explored.It was first proved that obviously coarsened conductive network of double percolation after scCO_(2) annealing was achieved,which benefited from CO_(2) plasticized polymer chains and thus decreased viscosity.Therefore,the electrical properties and electromagnetic interference(EMI)shielding performance of the composites were significantly improved.The percolation threshold of PLA/PS/MWCNT composites decreased from 0.31 wt.%to 0.16 wt.%,and EMI shielding effectiveness increased from 32.8 to 37.4 dB at 5 wt.%MWCNT loading.This work provides a simple,green,and effective way of post-processing to tailor the phase structure via varying conditions of annealing medium such as temperature,CO_(2) pressure,and time,and gains CPCs with improved electrical conductivity and EMI shielding performance.
