Enhanced dielectric properties of polyamide 11/multi‐walled carbon nanotubes composites

Composites with multi‐walled carbon nanotubes (MWNTs) involved in polyamide 11 (PA11) were prepared via a conventional melt blending method. The structure, morphology, crystallization behavior, electrical, and dielectric properties of composites were investigated. The results demonstrated that the dispersed uniformly MWNTs favored the formation of α crystal of PA11 when the composites were quenched from melt. The dielectric constant of composites was dependent on the electric field frequency and MWNTs content, and the highest value of dielectric constant was as high as 350 for the composite with 1.21 vol % MWNTs at 10³ Hz, accompanied by a low dielectric loss. The enhanced dielectric properties could be interpreted by the formation of abundant nanocapacitors within the composites and the interfacial polarization effect resulting from accumulation of charge carriers at the internal interfaces between MWNTs and PA11. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42642.     

碳纳米管/丙烯酸酯橡胶复合材料的制备及性能研究

采用自制的大分子表面改性剂对多壁碳纳米管(MWNTs)进行表面改性,制备改性MWNTs/丙烯酸酯橡胶(ACM)复合材料,研究改性MWNTs用量对复合材料性能的影响,并与炭黑补强的ACM性能进行对比.结果表明:用MWNTs填充ACM制备的材料,其性能远优于炭黑补强的ACM橡胶的性能;随着改性MWNTs用量的增大,复合材料...     

多壁碳纳米管／环氧树脂复合材料性能研究

采用物理机械方法与化学方法相结合的手段,制备了多壁碳纳米管（MWNTS）／环氧树脂（Epoxy）复合材料。通过力学拉伸试验测试了MWNTs/Epoxy复合材料拉伸强度和拉伸模量与MWNTS添加量的关系,利用扫描电镜（SEM）分析了MWNTS／Epoxy复合材料的拉伸断面,并用表面电阻测试仪对所制备的碳纳米管复合材料进行了电学性能测试。结果表明：经过化学酸化的方法处理后的MWNTS在复合材料中的分散得到了改善,力学性能也得到了明显的提高,但酸处理后的复合材料的电学性能明显低于未处理的复合材料。     

Electrical and dielectric properties of multiwall carbon nanotube/polyaniline composites

In this paper, electrical and dielectric properties of multiwall carbon nanotubes (MWCNTs)/insulating polyaniline (PANI) composites were studied. A mixture of MWCNTs and insulating polyaniline was dispersed in an ethanol solution by ultrasonic process, subsequently dried, and was hot-pressed at 200 °C under 30 MPa. Electrical and dielectric properties of the composites were measured. The experimental results show that the dc conductivities of the composites exhibit a typical percolation behavior with a low percolation threshold of 5.85 wt.% MWCNTs content. The dielectric constant of the composites increases remarkably with the increasing MWCNTs concentration, when the MWCNTs concentration was close to percolation threshold. This may be attributed to the critical behavior of the dielectric constant near the percolation threshold as well as to the polarization effects between the clusters inside the composites.     

Functionalization of multi-walled carbon nanotubes grafted with self-generated functional groups and their polyamide 6 composites

Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were applied in this study to demonstrate that multi-walled carbon nanotubes synthesized from ethanol flames (F-MWCNTs) inherently have functional groups on their surfaces. This finding clearly indicates that the covalent functionalization of carbon nanotubes can be achieved without oxidation as pretreatment. Thus, n-hexadecylamine functionalized F-MWCNTs (H-MWCNTs) can be synthesized simply, without disrupting the primary structures of the nanotubes. The melt-compounding method was used to fabricate polyamide 6/MWCNTs composites. Scanning electron microscope results confirmed that both F-MWCNTs and H-MWCNTs have much better nanoscopic dispersion in PA6 matrix than commercial MWCNTs, and the tensile strength, Young’s modulus, dynamic mechanical properties, and thermal behavior of their PA6 composites are considerably improved.     

多壁碳纳米管改性水泥基复合材料的性能研究

通过试验研究了多壁碳纳米管(MWCNTs)掺量对水泥净浆的力学性能、水化特性、凝结时间、孔隙分布等性能的影响,并采用SEM(扫描电镜)观察与分析了MWCNTs改性水泥净浆的微观形貌。结果表明,MWCNTs的掺入会降低水化过程中矿物的溶解速率,因而延缓了水泥的水化进程;在适宜的掺量范围内,MWCNTs能够有效提升水泥净浆的力学强度,但当其掺量过高时,反而会对力学强度造成不利影响;MWCNTs在水泥净浆中能够分散均匀并降低水泥净浆的孔隙率,使其变得更加密实。     

多壁碳纳米管改性水泥基复合材料的性能研究

通过试验研究了多壁碳纳米管(MWCNTs)掺量对水泥净浆的力学性能、水化特性、凝结时间、孔隙分布等性能的影响,并采用SEM(扫描电镜)观察与分析了MWCNTs改性水泥净浆的微观形貌。结果表明,MWCNTs的掺入会降低水化过程中矿物的溶解速率,因而延缓了水泥的水化进程;在适宜的掺量范围内,MWCNTs能够有效提升水泥净浆的力学强度,但当其掺量过高时,反而会对力学强度造成不利影响;MWCNTs在水泥净浆中能够分散均匀并降低水泥净浆的孔隙率,使其变得更加密实。     

动态硫化法制备多壁碳纳米管/热塑性硫化胶复合材料的热电性能（英文）

采用动态硫化法制备出多壁碳纳米管(MWCNTs)/热塑性硫化胶(TPV)复合材料。结果表明,MWCNTs/TPV复合材料具有"海岛"相结构,丁基橡胶相以微米级颗粒分散于聚丙烯(PP)相中,MWCNTs则主要分散于PP相及橡塑两相界面。当MWCNTs的质量分数达到渗滤阈值(3%)时可形成MWCNTs网络,致使复合材料的体积电阻率急剧减小,即MWCNTs/TPV复合材料的热电性能均因MWCNTs的存在而得到明显改善。     

Enhancement of physical and mechanical properties of polyamide 66 fibers using polysiloxane-functionalized multi-walled carbon nanotubes

A polyamide 66/3-aminopropyl-terminated poly(dimethylsiloxane) (PA66/APDMS)-carboxylate multiwalled carbon nanotubes (CMWNTs) nanocomposite (PA66/APDMS-CMWNTs) was synthesized using a one-pot method, and the product was melt-spun into fibers. The glass transition temperature (T_g) of the PA66/APDMS-CMWNTs nanocomposite fiber is 68.0°C, which is 22% higher than that of the pure PA66 fiber. This result indicates that there is a strong interfacial interaction between APDMS-CMWNTs and the PA66. Furthermore, the crystallinity of PA66/APDMS-CMWNTs nanocomposite fiber reaches a maximum due to the addition of APDMS-CMWNTs. Additionally, the tensile strength and Young's modulus of PA66/APDMS-CMWNTs nanocomposite fiber are 167% and 631% higher, respectively, than that of the pure PA66 fiber. The strengthening mechanism was discussed using force balance-based expression, which demonstrates that the stress on the PA66 is more efficiently transferred to the APDMS-CMWNTs. These results argue that using APDMS-CMWNTs as a filler can enhance the physical-mechanical properties of PA66 with an elevated degree never being reported.     

Preparation and properties of multi-walled carbon nanotube/carbon/polystyrene composites

Multi-walled carbon nanotube (MWCNT)/C/polystyrene (PS) composite materials were prepared by in situ polymerization of monomer in preformed MWCNT/C foams. MWCNT/C foams were preformed using polyurethane foam as template. The preformed MWCNT/C foams had a more continuous conductive structure than the carbon nanotube networks formed by free assembly in composites. The structure of the MWCNT/C foam network was characterized with scanning electron microscopy. The MWCNT/C/PS composites have an electric conductivity higher than 0.01 S/cm for a filler loading of 1 wt.%. Enhancement of thermal conductivity and mechanical properties by the preformed MWCNT/C foam were also observed.     

Improvements in interfacial and heat-resistant properties of carbon fiber/methylphenylsilicone resins composites by incorporating silica-coated multi-walled carbon nanotubes

The multi-scale reinforcement and interfacial strengthening on carbon fiber (CF)-reinforced methylphenylsilicone resin (MPSR) composites by adding silica-coated multi-walled carbon nanotubes (SiO₂-CNTs) were investigated. SiO₂-CNT has been successfully prepared via the hydrolysis of tetraethoxysilane in the presence of acid-oxidized multi-walled carbon nanotubes. Transmission electron microscopy, X-ray diffraction, and Fourier Transform infrared spectroscopy were carried out to examine the functional groups and structures of CNTs. Then, SiO₂-CNT was incorporated into MPSR matrix to prepare CF/MPSR-based composites by the compression molding method. The effects of the introduced SiO₂-CNT on the interfacial, impact, and heat-resistant properties of CF/MPSR composites were evaluated by short-beam bend method, impact test, and thermal oxygen aging experiments, respectively. Experimental results revealed that the CF/MPSR composites reinforced with 0.5 wt% SiO₂-CNT showed a significant increase 34.53% in the interlaminar shear strength (ILSS) and 20.10% in impact properties. Moreover, the heat-resistant properties of composites were enhanced significantly by adding SiO₂-CNT hybrid nanoparticles. These enhancements are mainly attributed to the improved matrix performance resulted from the molecular-level dispersion of SiO₂-CNT in MPSR matrix and the strong interfacial adhesion between SiO₂-CNT and matrix resin, which are beneficial to improve the mechanical stress transfer from MPSR matrix to CFs reinforcement and alleviate stress concentrations.     

可溶性碳纳米管与NR或CIIR复合材料性能的研究

通过有机改性制备可溶性碳纳米管（s—CNTs），采用溶液共沉法制备s—CNTs／NR和s—CNTs／CIIR复合材料，并对复合材料的性能进行研究。结果表明，通过有机改性制备的s—CNTs可均匀地分散于有机溶剂中；随s—CNTs用量增大，s-CNTs／NR复合材料邵尔A型硬度和密度增大，拉伸强度和拉断伸长率先增大后减小，s—CNTs／CIIR复合材料邵尔A型硬度和密度均增大，拉伸强度总体呈增大趋势，拉断伸长率变化不大，表面电阻率明显减小。     

Functional interphases with multi-walled carbon nanotubes in glass fibre/epoxy composites

The interphase between reinforcing fibre and matrix is a controlling element in composite performance. We deposited multi-walled carbon nanotubes (MWCNTs) onto electrically insulating glass fibre surfaces leading to the formation of semiconductive MWCNT-glass fibres and in turn multifunctional fibre/polymer interphases. The deposition process of MWCNTs onto glass fibre surfaces involved both electrophoretic deposition (EPD) and conventional dip coating methods. The EPD coating method produces a more homogeneous and continuous nanotube distribution on the glass fibre surface compared with the dip coating. According to fragmentation test results, the interphase with a small number of heterogeneous MWCNTs in the EPD fibre/epoxy composites, mimicking a biological bone structure, can remarkably improve the interfacial shear strength. We found that the semiconductive interphase results in a high sensitivity of the electrical resistance to the tensile strain of single glass fibre model composites. This material provides a possible in situ mechanical load sensor and early warning of fibre composite damage.     

Selective localization of multi-walled carbon nanotubes in epoxy/polyetherimide system and properties of the conductive composites

Multi-walled carbon nanotubes (MWCNTs) were introduced into the diglycidyl ether of a bisphenol A/polyetherimide (DGEBA/PEI) system. A co-continuous phase structure could be formed by the reaction-induced phase separation (RIPS). The MWCNTs localized selectively in PEI-rich phase which was predicted by theoretical calculations of the wetting coefficient (ω_a) and then confirmed both by optical microscopy and scanning electron microscopy. The thermomechanical properties of DGEBA/PEI/MWCNTs were studied by dynamic mechanical analysis. As the MWCNTs content increased from 0.5 to 1.0 wt %, storage modulus had a tendency of increasing monotonically from 2491 to 2948 MPa and the values of T_g for epoxy-rich phase were almost unchanged at about 130 °C. Subsequently, the result of electrical and thermal properties measurement for composites indicated that their volume resistivity decreased from 3.29 × 10¹⁵ to 3.86 × 10⁶ at 2.0 wt % MWCNTs and thermal conductivity were improved by 36.1% at the same time. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47911.     

Rheological and electrical properties of polypropylene composites containing functionalized multi-walled carbon nanotubes and compatibilizers

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized through acid, amine, and heat treatments. These were used in the manufacture of composites using polypropylene (PP) as matrix and two types of compatibilizers, maleic anhydride grafted polypropylene (MA-g-PP) and maleic anhydride grafted styrene-ethylene/butylene-styrene (MA-g-SEBS). PP/MWCNT composites filled with modified MWCNTs and compatibilizers were prepared by melt compounding with a twin-screw extruder and were evaluated to understand the effect of dispersion and interfacial interaction on the morphological, rheological, and electrical properties of the composite. When heat treated MWCNTs and compatibilizers were added to the composite, three dimensional network structures were generated through nanotube-nanotube and nanotube-matrix interactions resulting in percolation. Electrical conductivity was dramatically increased when the heat treated MWCNTs were added to the composite and was increased further with the addition of MA-g-SEBS compatibilizer.     

Facile synthesis and electrochemical capacitance of composites of polypyrrole/multi-walled carbon nanotubes

Composites of polypyrrole (PPy) and multi-walled carbon nanotubes (MWCNTs) were synthesized by a facile method involving one-step electrochemical deposition from a thin-layer of ionic liquid solution attached on a glassy carbon electrode. The morphology of the composites was characterized by field emission scanning electron microscopy, and the capacitance properties were investigated by cyclic voltammetry (CV). The charge-discharge behavior of the composites prepared in this work was examined by chronopotentiometry at a constant current density for multi-cycle scans. The results show that the PPy/MWCNT composites have a porous 3D nanostructure, with high specific capacitance (SC) of 890 F/g (for the mass of the PPy in the composites) calculated from CV at 2 mV/s in 1.0 M KCl. The stability of the composites in 1.0 M KCl electrolyte was also examined by multi-cycle CV and only 9% decrease of SC value was observed for the 1000 cycles.     

Fabrication of bimetallic nanoparticles/multi-walled carbon nanotubes composites for microelectronic circuits

A method for the fabrication of electrically-conducting polymer composites has been developed by mixing modified multi-walled carbon nanotubes (MWCNTs) functionalized by bimetallic nanoparticles (Ag/Ni/MWCNTs) into a UV curable resin. MWCNTs were treated by a concentrated H₂SO₄/HNO₃ mixture followed by ultrasonication with AgNO₃ and NiSO₄ in an ethylene glycol solution, producing MWCNTs decorated with Ag and Ni nanoparticles. The microstructure and surface morphology of the Ag/Ni/MWCNTs were investigated by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectrometry. It was found that the addition sequences of NiSO₄ and AgNO₃ influence the morphology of the Ag/Ni/MWCNTs. The electrically-conducting polymer composites were obtained by dispersing the prefabricated Ag/Ni/MWCNTs in UV curable resin, the curing process of which was tracked by Fourier transform infrared spectroscopy, and the electrical resistance was measured using the four-probe method. The fabrication of microelectronic patterns made by screen printing on different substrates was described.     

Improving tensile strength and toughness of melt processed polyamide 6/multiwalled carbon nanotube composites by in situ polymerization and filler surface functionalization

The effect of processing method and condition on the dispersion status of multiwalled carbon nanotubes (MWCNTs), and mechanical properties of the MWCNT/polyamide 6 (PA6) composites are investigated. Different melt processing conditions are used to dilute the master batch produced by melt process or in situ polymerization. Both MWCNTs and carboxyl group functionalized MWCNTs (MWCNTs‐COOH) are compounded with PA6 at different loadings (0.1, 0.25, 0.5, and 0.75 wt %) to study the effect of chemical modification of MWCNTs on the mechanical properties of the final composites. It is demonstrated that chemical modification of MWCNTs has a positive effect on the strength of the composites as an increase of 5–10 MPa was observed. More importantly, a near 5 MPa increase in strength and more importantly, a maximum of 138% increase in strain at break were observed for the composites produced by in situ polymerization, indicating a toughening and strengthening effect of CNT on the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation on the multiwalled carbon nanotubes reinforced polyamide 6/polypropylene composites

Multiwalled carbon nanotubes (MWNTs) reinforced polyamide 6/polypropylene (PA6/PP = 70/30) composites were prepared by melt compounding. Maleated polypropylene (MPP) was used as a compatibilizer for the composites. The morphology, mechanical properties, thermal stability, rheological properties and crystallization behavior of the composites were investigated. It was found that the addition of MWNTs to PA6/PP blend resulted in decrease in the size of the dispersed particles. Most of MWNTs were selectively dispersed in the PA6 phase and a small amount of MWNTs were located in the interphase between PA6 matrix and PP phase as characterized by scanning electric microscopy. The strength and stiffness of the PA6/PP blend were greatly improved by the addition of MWNTs. The MPP and MWNTs had a synergistic effect on the improvement ofthe thermal stability. In addition, the complex viscosity, storage modulus and loss modulus of the composites increased with the addition of MWNTs or MPP. MWNTs could induce the formation of α crystalline form of PA6. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers