Effects of electrically inert fillers on the properties of poly(<Emphasis Type="Italic">m</Emphasis>-xylene adipamide)/multiwalled carbon nanotube composites

The effects of three types of electrically-inert fillers, calcium carbonate (CaCO₃), talc and glass fiber (GF), on electrical resistivity, crystallization behavior and dynamic mechanical properties of poly(m-xylene adipamide) (MXD6)/multiwalled carbon nanotube (MWCNT) composites are investigated. The electrical resistivity of MXD6/MWCNT composites is significantly reduced with the addition of inert fillers due to the volume-exclusion effect that leads to increased effective concentration of MWCNTs in MXD6 matrix and also due to improved MWCNT dispersion. The crystallization temperature of MXD6 increases with the addition of MWCNTs, indicating that MWCNTs can act as nucleating agent and induce crystallization of MXD6. The incorporation of inert fillers has no further effect on crystallization behavior of MXD6, but significantly improves the storage modulus of MXD6/MWCNT composite, demonstrating that CaCO₃, talc and GF filled MXD6/MWCNT composites are very promising materials with not only improved electrical property but also excellent mechanical properties.     

玻璃纤维对聚甲醛基导电复合材料性能的影响

采用在转矩流变仪中熔融混合的方法制备了聚甲醛(POM)/多壁碳纳米管(MWCNTs)/玻璃纤维(GF)和POM/炭黑(CB)/GF复合材料,研究了GF的加入对复合材料的导电性能、结晶行为和动态力学性能的影响.采用场发射扫描电镜(FESEM)观察了复合材料中导电填料的分散状态,发现GF的加入对MWCNTs和CB的分散状态没有明显影响.虽然GF为导电惰性填料,但因其加入起到了占位作用,明显提高了导电填料的有效浓度,从而使复合材料的体积电阻率明显降低.采用示差扫描量热仪(DSC)研究了复合材料中POM的结晶行为,发现GF的加入对POM的结晶温度、熔点和结晶度均无明显影响.采用动态机械分析仪(DMA)对复合材料的动态力学性能进行了研究,表明GF的加入能够明显地提高复合材料的储能模量.     

玻璃纤维对碳纳米管填充聚合物/热塑性聚氨酯共混体系导电性能的影响

研究了表面带有环氧基团的玻璃纤维(GF)对聚丙烯(PP)/热塑性聚氨酯(TPU)/多壁碳纳米管(MWCNT)、 聚甲基丙烯酸甲酯(PMMA)/TPU/MWCNT和聚乳酸(PLA)/TPU/MWCNT体系导电性能的影响. 研究结果表明, 未添加GF时, 由于MWCNTs选择性地分布在TPU分散相中, PP/TPU/MWCNT, PMMA/TPU/MWCNT和PLA/TPU/MWCNT材料的导电性能很差; 加入20%的GF使3个体系的电阻率均大幅度下降, 最高下降约13个数量级, 表明填充GF是一种具有普适性的改善以TPU为分散相的共混体系导电性能的有效方法. GF使体系电阻率降低的机理主要是形成了TPU包覆GF结构, 该结构可以看作长径比较高的导电棒, 可以有效协助导电通路的构建; 同时GF还起到了体积占位的作用, 提高了体系中导电组分在基体中的有效浓度.     

Influence of talc with different particle sizes in melt‐mixed LLDPE/MWCNT composites

Linear low‐density polyethylene (LLDPE) was melt‐mixed with multiwalled carbon nanotubes (MWCNTs) and varying amounts of three different kinds of talc (phyllo silicate), each with a different particle size distribution, to examine the effect of these filler combinations with regards to the electrical percolation behavior. The state of the filler dispersion was assessed using transmission light microscopy and electron microscopy. The use of talc as a second filler during the melt mixing of LLDPE/MWCNT composites resulted in an improvement in the dispersion of the MWCNTs and a decrease of the electrical percolation threshold. Talc with lower particle sizes showed a more pronounced effect than talc with larger particle sizes. However, the improvement in dispersion was not reflected in the mechanical properties. Modulus and stress values increase with both, MWCNT and talc addition, but not in a synergistic manner. The crystallization behavior of the composites was studied by differential scanning calorimetry to determine its potential influence on the electrical percolation threshold. It was found that the crystallinity of the matrix increased slightly with the addition of talc but no further increments were observed with the incorporation of the MWCNTs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1680–1691     

Influence of organo-clay on electrical and mechanical properties of PP/MWCNT/OC nanocomposites

The electrical, thermal and mechanical properties of nanocomposites, based on polypropylene (PP) filled by multi-walled carbon nanotubes (MWCNTs) and organo-clay (OC), were studied with the purpose of finding out the effect of OC on the microstructure of MWCNTs dispersion and PP/MWCNT/OC composites. It was found that addition of organo-clay nanoparticles improved nanotube dispersion and enhanced electrical properties of PP/MWCNT nanocomposites. Addition of organo-clay (MWCNT/OC ratio was 1/1) reduced the percolation threshold of PP/MWCNT nanocomposites from ?_c = 0.95 vol.% to ?_c = 0.68 vol.% of carbon nanotubes, while the level of conductivity became 2–4 orders of magnitude higher. The DSC and DMA analyses have shown that the influence of organo-clay on the thermal and mechanical properties of material was not significant in composites with both fillers as compared to PP/OC. Such an effect can be caused by stronger interaction of OC with carbon nanotubes than with polymer matrix.     

Complementary effects of multiwalled carbon nanotubes and conductive carbon black on polyamide 6

This article introduces a newly innovative idea for preparation of superconductive ternary polymeric composites of polyamide 6 (PA6), conductive carbon black (CCB), and multiwalled carbon nanotubes (MWCNTs) with different weight ratios by a melt‐mixing technique. The complementary effects of CCB and MWCNTs at different compositions on rheological, physical, morphological, thermal, and dynamic mechanical and electrical properties of the ternary composites have been examined systematically. We have used a novel formulation to produce high‐weight fraction ternary polymer composites that show extremely higher conductivity when compared with their corresponding binary polymer composites at the same carbon loading. For example, with an addition of 10 wt % MWCNTs into the CCB/PA6 composite preloaded with 10 wt % CCB, the electrical conductivity of these ternary composites was about 5 S/m, which was 10 times that of the CCB/PA6 binary composite (0.5 S/m) and 125 times that of the MWCNT/PA6 binary composite (0.04 S/m) at 20 wt % carbon loading. The incorporation of the MWCNTs effectively enhanced the thermal stability and crystallization of the PA6 matrix in the CCB/PA6 composites through heterogeneous nucleation. The MWCNTs appeared to significantly affect the mechanical and rheological properties of the PA6 in the CCB/PA6 composites, a way notably dependent on the MWCNT contents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1203–1212, 2010     

In situ polymerization of methyl methacrylate/multi-walled carbon nanotube composites using cationic stearyl methacrylate copolymers as dispersants

Novel water-soluble amphiphilic copolymers (poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)]) for dispersing multi-walled carbon nanotubes (MWCNTs) were used to carry out in situ methyl methacrylate (MMA) polymerization. The morphology of the poly(methyl methacrylate)/MWCNT composites and the dispersion of the MWCNTs were analyzed by transmission electron microscopy. The dispersion of multi-walled carbon nanotubes in the composites was excellent for cationic SMA (stearyl methacrylate) copolymers, even at high MWCNT loading (6.0 wt.%). The mechanical properties and electrical and thermal conductivities of the composites were also analyzed. Mechanical properties were improved by MWCNTs; the strain at break values remained stable up to 6.0 wt.% MWCNT loading. Both electrical and thermal conductivities were improved by the addition of MWCNTs.     

Significant enhancement of electrical and thermal conductivities of polyethylene carbon nanotube composites by the addition of a low amount of silver nanoparticles

Electrically and thermally conductive high‐density polyethylene composites filled with hybrid fillers, multiwall carbon nanotubes (MWCNTs) and silver nanoparticles (Ag‐NPs), have been prepared in the melt state. The investigation of their electrical and thermal conductivities while comparing with high‐density polyethylene/MWCNT binary composites shows that the addition of only 3 vol% of Ag‐NPs does not reduce the electrical percolation threshold (P_c) that remains as low as 0.40 vol% of MWCNTs but leads to an increase in the maximum dc electrical conductivity of PE/MWCNT composites by two orders of magnitudes. Moreover, the association of both Ag‐NPs and carbon nanotube particles improved our composite's thermal conductivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Rheological and electrical properties of polypropylene/MWCNT composites prepared with MWCNT masterbatch chips

Melt compounded PP/MWCNT (polypropylene/multi-walled carbon nanotube) composites were prepared by diluting highly concentrated masterbatch chips. Maleic anhydride grafted polypropylene (PP-g-MAH) was used as a compatibilizer to promote dispersion and interaction of MWCNTs. Rheological properties were investigated with respect to the MWCNT and compatibilizer loadings, and related to morphological and electrical properties. As the MWCNT loading was increased, shear viscosity and yield stress were increased at low shear rate region because of increased interaction between MWCNT particles. When the MWCNT loading was low, MWCNT dispersion was improved by the PP-g-MAH compatibilizer because MWCNTs were wetted sufficiently due to the presence of the compatibilizer. However, rheological and electrical properties of highly concentrated MWCNT composites with the compatibilizer were not improved compared with PP/MWCNT composites without the compatibilizer because the compatibilizer did not provide sufficient wrapping of MWCNT particles. Electrical and morphological properties of PP/MWCNT composites were correlated with the rheological properties in steady and dynamic oscillatory shear flows.     

The effect of crystallization behavior on high conductivity,enhanced mechanism and thermal stability of poly(ε-caprolactone)/multi-walled carbon nanotube composites

Poly(ε-caprolactone) (PCL) composites filled by multi-walled carbon nanotubes (MWCNTs) which was non-covalently modified by the combined surfactants of poly(sodium 4-styrenesulfonate) and cetyltrimethyl-ammonium bromide (PSS-CTAB) were fabricated via simple solution precipitation method. PCL/MWCNTs composites provided with the low procolation threshold (0.4?wt%) and high electrical conductivity due to good dispersion of MWCNTs. And the excellent mechanical properties and enhanced thermal stability were also obtained with the addition of modified MWCNTs. In addition, all PCL composites showed significantly enhanced crystallization with increasing the MWCNTs contents, which demonstrated that the MWCNT-induced crystallization of PCL could effectively regulate the properties of composites. In a word, introducing non-covalent functionalized MWCNTs in the polymer system was a promising way for developing excellent conductive composites.     

碳纳米管改性聚苯硫醚熔纺纤维的结构与性能研究

将多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)经过熔融挤出后制备成复合材料切片,并采用熔融纺丝法制得碳纳米管改性聚苯硫醚复合纤维.采用扫描电镜(SEM)、拉曼光谱、示差扫描量热分析(DSC)、动态机械分析(DMA)以及力学性能测试等表征手段研究了复合纤维中碳管的分散状态,与基体的界面作用,复合纤维的结晶性能以及力学性能,从而探讨了聚苯硫醚/碳纳米管复合纤维体系的微观结构与宏观性能之间的关系.研究表明,聚苯硫醚分子结构与碳纳米管之间具有的π-π共轭作用使碳管较为均匀的分散在基体中,界面结合较为紧密.同时熔融纺丝过程中的拉伸作用使碳管进一步解缠并使碳管沿纤维拉伸方向取向.另一方面,拉曼光谱显示拉伸作用有效地增强了界面作用,有利于外界应力的传递.碳管的良好分散以及强的界面作用使复合纤维力学性能得到大幅度的提高,当碳管含量达到5 wt%时,复合纤维的模量有了明显的提高,拉伸强度较纯PPS纤维提高了近220%.     

十二烷基硫酸钠对多壁碳纳米管/聚对苯二甲酸乙二酯复合材料性能的影响

用十二烷基硫酸钠(SDS)作为一种改性剂处理多壁碳纳米管(MWCNT),SDS处理后的MWCNT命名为SCNT,并采用微型挤出机和微型注塑机分别制备了MWCNT/PET和SCNT/PET复合材料.从材料的微观结构,导电性能,结晶性能和机械性能等角度,研究了SDS对MWCNT/PET复合材料性能的影响.结果表明,SDS处...     

多壁碳纳米管对聚甲醛性能的影响

将多壁碳纳米管(MWCNTs)和聚甲醛(POM)在转矩流变仪中熔融混合得到POM/MWCNT复合材料.研究了复合材料的形态,导热性能,导电性能,流变性能和结晶性能.结果表明,MWCNTs在没有经过处理的情况下能够均匀地分散在POM基体中;当向POM中添加1.0 wt%含量MWCNTs时,复合材料的导热系数上升到0.5289 W/(K m),比纯POM的导热系数0.198 W/(K m)提高1.5倍,通过有效介质方法(EMA)验证了体系导热系数提高幅度不大的原因是MWCNTs与POM之间形成了很高的界面热阻;当MWCNTs的含量为1.0 wt%时,体系产生了导电逾渗效应,逾渗值在0.5 wt%~1.0 wt%之间;MWCNTs对POM有显著的成核作用,当向POM中添加0.5 wt%含量的MWCNTs时,POM的结晶温度提高6℃左右,但当MWCNTs的添加量进一步增加时,结晶温度几乎不再变化,成核效果呈现"饱和"状态.另外,材料的复数黏度,储能模量和损耗模量随MWCNTs含量的增加而增加.     

Strengthening of liquid crystalline polymer by functionalized carbon nanotubes through interfacial interaction and homogeneous dispersion

Multiwalled carbon nanotubes (MWCNTs) were functionalized with two types of chemical moieties (i.e. carboxylic, ? COOH and hydroxyl benzoic acid groups, ‐HBA) on their sidewalls in order to improve their interaction with a liquid crystalline polymer (LCP) and dispersion in LCP. We have investigated the rheological, mechanical, dynamic mechanical, and thermal properties in detail with variation of HBA‐functionalized MWCNTs in the LCP matrix. Effect of the dispersion state of the functionalized MWCNTs in the LCP matrix on the rheological behavior was also studied. The composites containing HBA‐functionalized MWCNTs showed higher complex viscosity, storage, and loss modulus than the composites with the same loading of raw MWCNTs and MWCNT‐COOH. It was suggested that the HBA‐functionalized MWCNTs exhibited a better dispersion in the polymer matrix and formed stronger CNT‐polymer interaction in the composites than the raw MWCNTs and MWCNT‐COOH, which was also confirmed by FESEM and FTIR studies. As a result, the overall mechanical performance of the HBA‐MWCNT‐LCP composites could be improved significantly. For example, the addition of 4 wt% HBA‐MWCNT to LCP resulted in the considerable improvements in the tensile strength and modulus of LCP (by 66 and 90%, respectively). Copyright © 2010 John Wiley & Sons, Ltd.     

表面复合纳米SiO_2和碳纳米管玻璃纤维增强尼龙6的结构与性能

利用静电相互作用在玻璃纤维(GF)表面分别复合纳米二氧化硅(SiO2)和多壁碳纳米管(MWNTs),制备了GF-SiO2、GF-MWNTs复合增强体,并通过转矩流变仪制备了尼龙6(PA6)/GF-SiO2和尼龙6(PA6)/GF-MWNTs复合材料.利用扫描电子显微镜(SEM),示差扫描量热仪(DSC),热机械分析仪(DMA)等手段研究了复合材料的微观结构、热学及力学性能.结果表明,静电复合的方法可以使纳米二氧化硅(nano-SiO2)、多壁碳纳米管(MWNTs)在GF表面达到均匀吸附,复合增强体能加快尼龙6的结晶速度,并使材料的玻璃化温度、动态模量、拉伸强度、结晶温度等明显提高,其中GF-MWNTs对复合材料性能的提高最明显,拉伸强度提升了21%,模量提高了28%.     

Crystallization and reinforcement of poly (vinylidene fluoride) nanocomposites: Role of high molecular weight resin and carbon nanotubes

The effect of high molecular weight resin and multi-walled carbon nanotubes (MWCNTs) on the crystallization, rheological and dynamic mechanical properties of poly (vinylidene fluoride) (PVDF) composites was investigated. A synergetic effect of the high molecular weight resin and MWCNTs on the nucleation in the crystallization process of the matrix has been observed, and their contributions to the crystallization of the matrix are two-sided. The composites containing both the high molecular weight resin and MWCNTs have much higher crystallization peak temperatures but lower crystallinity, especially for samples with high MWCNT content. For the isothermal crystallization at relative high temperatures, higher Avrami exponent and shorter half-time of crystallization are observed for the composites containing both the high molecular weight resin and MWCNTs. The introduction of the high molecular weight resin not only reinforces the matrix, but also promotes the dispersion of MWCNTs. The reinforcement and synergetic nucleation effects of the high molecular weight resin and MWCNTs were also confirmed by dynamic mechanical analysis.     

Improvement of thermal conductivity of poly(dimethyl siloxane) using silica-coated multi-walled carbon nanotube

In order to enhance the thermal conductivity of MWCNT filled poly(dimethyl siloxane) (PDMS) composites, the MWCNT was coated with silica layer by three step reactions. The composites filled with raw and silica-coated MWCNTs were prepared and the properties were investigated in terms of the curing characteristics, mechanical properties, and thermal conductivity. Due to the poor compatibility between raw MWCNT and PDMS, raw MWCNT showed poor dispersion uniformity and wettability in PDMS. On the other hand, due to the chemical affinity between silica/MWCNT and PDMS throughout the hydrogen bonding, the silica-coated MWCNT filled PDMS showed improved mechanical properties in terms of tensile strength and 100% modulus, and good interfacial compatibility than raw MWCNT incorporated PDMS. Finally, the good wettability of silica/MWCNT in PDMS resulted in higher thermal conductivity caused from the facile phonon movement at the interface even with the smaller MWCNT contents.     

New melt mixing polyethylene multiwalled carbon nanotube nanocomposites with very low electrical percolation threshold

The present work focuses on the study of the electrical properties of high‐density polyethylene (HDPE)/multiwalled carbon nanotube (MWCNT) nanocomposites. The samples were produced by melt mixing by diluting a masterbatch of HDPE/MWCNT using two types of mini‐extruders in order to see the influence of the shear processing on the electrical properties. The dielectric relaxation spectroscopy was used for the investigation of the electrical properties in the studied samples. The composites dc conductivity (σ_dc) follows the scaling low derivate from the percolation theory of the form σ_dc ~ (p ? p_c)^t. A low electrical percolation (p_c ≈ 0.3 ? 0.4 vol. %) was found in both cases. The critical exponent t had a value very close to the theoretical one for a percolation network in three dimensions (t ≈ 2). The analysis of the morphology of the nanocomposites showed a good and homogeneous dispersion of the fillers in the PE matrix. The effect of the incorporation of MWCNTs on the dynamic mechanical and thermal behaviors was also presented. The MWCNTs have improved the mechanical properties of the polyethylene matrix and increased the crystallization temperatures. Copyright © 2013 John Wiley & Sons, Ltd.     

Contribution of oriented structure and rigid nanofillers to mechanical enhancement of die-drawn PP/MWCNT composites

Oriented structure, mainly controlled by processing conditions, is another efficient method of reinforcing polymer materials in addition to compounding with rigid inorganic fillers such as carbon nanotubes (CNTs). The mechanical properties of oriented polypropylene (PP)/multiwalled CNT (MWCNT) composites, which are vital to their application fields, are investigated extensively in this paper, with an aim to distinguish the contribution of MWCNTs contents from that of the oriented structure to the final performance of the composite. The results indicate that MWCNTs mainly increase the modulus of the composites by approximately 140%. The oriented structure formed during the die-drawing process contributes more to the enhancement of tensile strength, increasing up to 550%. The modulus and tensile strength can be further improved by increasing the drawing speed. Moreover, the tensile stress field in the die-drawing process can vastly improve the dispersion of the MWCNTs in the matrix, thus providing a new idea for improving the dispersion of nanofillers in the polymer matrix.     

Preparation of polystyrene/MWCNT‐Valine composites: Investigation of optical,morphological, thermal,and electrical conductivity properties

The attempt of this research was to examine the effect of multiwalled carbon nanotube (MWCNT)‐Valine as efficient fillers on the thermal, optical, and electrical behaviors of polystyrene (PS). To reduce aggregation and obtain uniform spreading of fillers into the PS, at first, MWCNTs' surfaces were modified by Valine amino acid. Then, different contents of MWCNT‐Valine (0.5, 1, and 2 wt%) were added to PS by ultrasonication processes. The field emission scanning electron microscopy and transmission electron microscopy results showed a uniform distribution of modified MWCNTs into the matrix. The thermal properties of nanocomposites were improved by increasing nanofiller content. In addition, embedding of MWCNT‐Valine into the PS matrix increased the electrical conductivity of nanocomposites in comparison with pure PS.