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1.
It is known that the electrical volume resistivity of insulating polymers filled with conductive fillers suddenly decreases at a certain content of filler. This phenomenon is called percolation. Therefore, it is known that controlling resistivity in the semi-conductive region for carbon black (CB) filled composites is very difficult. When poly (ethylene-co-vinyl acetate) (EVA) is used as a matrix, the percolation curve becomes gradual because CB particles disperse well in EVA. In this study, the relationship between the dispersion state of CB particles and electrical resistivity for EVA/poly (L-lactic acid) (PLLA) filled with CB composite was investigated. The apparent phase separation was seen in the SEM photograph. It was predicted that the CB particles located into the EVA phase in the light of thermodynamical consideration, which was estimated from the wetting coefficient between polymer matrix and CB particles. The total surface area per unit mass of dispersed CB particles in the polymer blend matrix was estimated from small-angle X-ray scattering and the volume resistivity decreased with increasing CB content. The values of the surface area of CB particles in CB filled EVA/PLLA (25/75 wt%) and EVA/PLLA (50/50 wt%) polymer blends showed a value similar to that of the CB filled EVA single polymer matrix. In electrical volume resistivity measurement, moreover, the slopes of percolation curves of EVA/PLLA (25/75 wt%) and EVA/PLLA (50/50 wt%) filled with CB composite are similar to that of EVA single polymer filled with CB composite. As a result, it was found that CB particles selectively locate in the EVA phase, and then the particle forms conductive networks similar to the networks in the case of EVA single polymer used as a matrix. 相似文献
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Ming Yuan José C. M. Brokken‐Zijp Gijsbertus De With 《Journal of Polymer Science.Polymer Physics》2009,47(4):366-380
A new and straightforward method has been studied to prepare crosslinked low surface energy semiconductive epoxy coatings. The low surface energy is obtained by adding a small amount of partially fluorinated bifunctional primary amine Jeffamine D230 crosslinker and the conductivity is achieved by adding a small amount of semiconductive nanosized Cobalt(III) phthalocyanine particles. The use of partially fluorinated crosslinker strongly influences the conductivity, the conductive particle network structure, and the network distribution in the coatings. Compared to coatings that are free of fluorine, variations in fractal dimension, percolation threshold, particle‐containing layer thickness, and conductivity level are observed as the amount of fluorinated species is varied. These differences can be explained by (local) differences in effective Hamaker constant, viscosity, curing rate, evaporation of the solvent, and presence or absence of polymer matrix between the particles in the network. Our results suggest that other crosslinked semiconductive low surface energy epoxy coatings can be realized in a similar manner, but careful optimization of processing conditions is required to obtain the desired conductivity levels at low filler concentration. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Chem 47: 366–380, 2009 相似文献
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Petra P?tschke Mahmoud Abdel-Goad Sven Pegel Dieter Jehnichen James E. Mark Donghui Zhou 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):12-19
The present investigation compares different carbon-based nanoscaled materials with regard to their effectiveness in producing thermoplastic polymers with antistatic and electrically conductive behavior. The dispersed phases are carbon black (CB) as spherical particles, multiwalled carbon nanotubes (MWNT) as fiber-like filler, and expanded graphite (EG) as platelet-like filler. Each was incorporated into polycarbonate by small-scale melt mixing. The electrical percolation concentrations were found to be 2 wt% for MWNT, 4 wt% for EG, and 8.75 wt% for CB which parallels the aspect ratios of the fillers. For EG a strong dependence of morphology and electrical resistivity on mixing time was observed, indicating a structural change/destruction during intensive shear mixing. Rheological percolation thresholds were found to be lower than electrical percolation threshold for the MWNT and CB, but similar in the case of EG. The general impact on complex melt viscosity decreases in the order MWNT, CB, EG. For EG, at higher loadings (above 4wt%) the viscosity increase with filler content is delayed as is the decrease in resistivity. 相似文献
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聚乙烯/聚并苯复合材料室温电阻率变化规律研究 总被引:3,自引:1,他引:2
以新型导电材料聚并苯替代碳黑作为导电填料制备聚乙烯/聚并苯复合物.确定了复合物渗流转变区,并解释渗流转变现象的产生机理.从聚并苯含量和热处理过程,对聚乙烯/聚并苯复合物室温电阻率变化规律进行讨论.结果表明,聚并苯质量分数在20%~40%之间是聚乙烯/聚并苯复合物渗流转变区;热处理有利于聚乙烯晶区完善排列,也有利于导电链形成;以聚并苯作为导电填料所制备的复合物具有较高的PTC强度;辐射交联可以提高聚乙烯/聚并苯复合物PTC强度,抑制NTC效应. 相似文献
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碳纳米管/炭黑混杂填充聚甲醛复合材料导电性能研究 总被引:1,自引:0,他引:1
采用在转矩流变仪中熔融混合的方法制备了多壁碳纳米管(MWCNTs)和导电炭黑(CB)共同填充的聚甲醛(POM)导电复合材料,研究了材料的体积电阻率和导电填料用量之间的关系.用该体系的实验数据点对已发表的混合导电填料体系的定量关系式进行了验证,结果表明实验数据点和理论预测略有偏差.为方便实际应用,把混合导电填料体系的定量关系式加以发展,推导出逾渗值和两种导电填料质量比之间的关系式,并绘出了工作曲线.设计实验对工作曲线进行了验证,结果表明工作曲线对实践具有指导意义. 相似文献
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研究了炭黑(CB)和石墨(GP)填充高密度聚乙烯(HDPE)复合体系的动态流变行为.发现高填料含量时出现似固体行为,并认为它归因于无机粒子网络逾渗结构的形成.在相同聚合物基体条件下,粒子种类和粒子几何参数(粒子形状、大小、粒径分布)对低频区域流变行为、流变参数的逾渗行为和逾渗阈值(φc)有决定性影响,且种类的影响相比于粒子几何参数更为显著.此外,高表面活性及高比表面积(大径厚比、小尺寸)粒子填充体系具有较低的φc. 相似文献
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用Haake转矩流变仪制备了聚对苯二甲酸乙二酯-聚乙烯-炭黑(PET-PE-CB)复合材料.通过溶解性试验、扫描电镜测试对CB在PET-PE多相体系中的选择性分散进行了研究,考察了CB分布对电性能的影响.结果表明:CB倾向于分布在PET相,改变CB填充量、基体配比以及加料次序对CB微观分布的影响不大.当m(CB)/m(PET-PE)=0.07时,出现渗滤现象.固定炭黑含量,当PET的质量分数由20%增加到60%时,材料的体积电阻率下降了6个数量级,一次性加料更有利于形成导电通路,可以获得较低的体积电阻. 相似文献
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电响应聚合物薄膜的表面图案化 总被引:9,自引:0,他引:9
研究了炭黑(CB)和石墨(GP)填充高密度聚乙烯(HDPE)复合体系的动态流变行为.发现高填料含量时出现似固体行为,并认为它归因于无机粒子网络逾渗结构的形成.在相同聚合物基体条件下,粒子种类和粒子几何参数(粒子形状、大小、粒径分布)对低频区域流变行为、流变参数的逾渗行为和逾渗阈值(φc)有决定性影响,且种类的影响相比于粒子几何参数更为显著.此外,高表面活性及高比表面积(大径厚比、小尺寸)粒子填充体系具有较低的φc. 相似文献
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Stephen H. Foulger 《Journal of Polymer Science.Polymer Physics》1999,37(15):1899-1910
The DC conductivity of polymer blends composed of poly(ethylene‐co‐vinyl acetate) (EVA) and high density polyethylene (HDPE), where a conductive carbon black (CB) had been preferentially blended into the HDPE, were investigated to establish the percolation characteristics. The blends exhibited reduced percolation thresholds and enhanced conductivities above that of the individually carbon filled HDPE and EVA. The percolation threshold of the EVA/HDPE/CB composites was between 3.6 and 4.2 wt % carbon black, where the volume resistivity changed by 8 orders of magnitude. This threshold is at a significantly lower carbon content than the individually filled HDPE or EVA. At a carbon black loading of 4.8 wt %, the EVA/HDPE/CB composite exhibits a volume resistivity which is approximately 14 and 11 orders of magnitude lower than the HDPE/CB and EVA/CB systems, respectively, at the same level of incorporated carbon black. The dielectric response of the ternary composites, at a temperature of 23°C and frequency of 1 kHz, exhibited an abrupt increase of ca. 252% at a carbon concentration of 4.8 wt %, suggesting that the percolation threshold is somewhat higher than the range predicted from DC conductivity measurements. Percolating composites with increasing levels of carbon black exhibit significantly greater relative permittivity and dielectric loss factors, with the composite containing 6 wt % of carbon black having a value of ϵ′ ≈ 79 and ϵ″ ≈ 14. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1899–1910, 1999 相似文献
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合成了三种新型的有机电子受体: N,N'-二(2-氟代苯基)-3,4,9,10-苝四羧基二酰亚胺(D2MFPP)、N,N'-二(3-氟代苯基)-3,4,9,10-苝四羧基二酰亚胺(D3MFPP)和N,N'-二(4-氟代苯基)-3,4,9,10-苝四羧基二酰亚胺(D4MFPP). 利用元素分析、傅立叶变换红外(FTIR)等方法表征了它们的分子结构, 用紫外-可见光吸收光谱(UV-Vis)、X射线衍射(XRD)和原子力显微镜(AFM)等手段研究了氟代位置对苝酰亚胺薄膜聚集态结构的影响, 发现氟代使苝酰亚胺的聚集态发生变化, 且不同位置的氟代对其影响也不一样. 除了分子结构的影响, 外场条件也会产生很大的作用. 通过制备场效应晶体管研究了其电子传输性能, 发现氟代后器件的空气稳定性有明显提高. 相似文献
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In the present work broadband dielectric relaxation spectroscopy measurements were employed to investigate the dielectric properties of polymer composites. A polyethylene/polyoxymethylene (PE/POM) thermoplastic blend was used as a matrix, while the inclusions were iron (Fe) particles. For comparison, the two pure polymers- PE and POM- were used as a matrix, too. In the PE/POM-Fe composites, the polymer matrix is two-phase and the filler particles are localized only in the POM phase, resulting in an ordered distribution of the dispersed filler particles within the blend. In PE-Fe and POM-Fe composites, the filler spatial distribution is random. The behaviour of all the composites studied is described in terms of the percolation theory. The PE/POM-Fe composites, based on the PE/POM blend, demonstrate different electrical behaviour compared to that of POM-Fe and PE-Fe systems. The percolation threshold value of the PE/POM-Fe composites was found much lower than that of the other two systems. The results were related to the microstructure of the composites. A schematic model for the morphology of the composites studied has been proposed. This model explains the peculiar behaviour of the PE/POM-Fe composites by taking into account the ordered distribution of the filler particles in a binary polymer matrix. Optical microscopy photographs confirm this model. 相似文献
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CB/HDPE导电复合体系中Kerner-Nielson方程修正及电渗流与粘弹渗流的相关性 总被引:3,自引:0,他引:3
随着导电填料含量的增加,聚合物导电复合材料的电导率呈现非连续的递增.当填料含量达到渗流阈值并导致渗流现象出现时,导电填料相互聚集并形成网络,体系电导率急剧增大,关于此类电渗流现象已有很多报道[1~4].填充类导电复合材料的结构和性能与其粘弹性密切相关.近年来,由于炭黑填充使得许多光学方法失效,流变学方法受到了广泛重视.最新的研究发现,非均相结构的出现和演化对浓度的依赖性有着特征流变响应,是一种粘弹渗流现象[5~7]. 相似文献
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Kingsley K.C. Ho George Shia Alexander Bismarck 《Journal of fluorine chemistry》2007,128(11):1359-1368
The development of ultra-inert composites using fluorinated carbon fibres as the reinforcement requires fluorinated carbon fibres with a durable surface composition. Here we report the effect of direct fluorination using an F2/N2 mixture at 653 K on the surface and bulk properties of two types of high strength carbon fibres. These were treated up to a surface fluorine content of ∼64 at.% and a bulk fluorine content of ∼15 mass%. A colour change was observed after fluorination caused by the changes in the graphitic band structure of the carbon fibres by the introduction of carbon sp3 hybridisation. The tensile strength and Young's modulus decrease after fluorination by up to 33 and 22%, respectively. XRD shows marginal changes in the interlayer distance but the crystallite size increases. Changes in the electrical conductivity of the fluorinated carbon fibres indicate that the modification is confined to the near surface volume. Predominantly covalent C-F bonds are formed as shown by X-ray photoelectron spectroscopy (XPS) and measured zeta (ζ)-potentials. Hence the fluorinated fibres are hydrophobic and have low surface tensions. This and the large increase in fibre surface area, as determined by nitrogen adsorption, is expected to facilitate interfacial interaction between fluorinated carbon fibres and fluoropolymers. 相似文献
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Ana Maria Ferraria 《Journal of fluorine chemistry》2004,125(7):1087-1094
A fluorination reactor was designed and built in the laboratory. The optimal conditions of fluorination within the reactor were selected by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis of fluorinated surfaces of a film and a plaque of pure high-density polyethylene (HDPE). This reactor was used to post-mould fluorinate plaques and films of a range of mixtures of virgin and recycled HDPE with and without (re)introduction of additives. The ability to be fluorinated has shown no dependence on the composition virgin/recycled HDPE.Comparison of in-line and post-mould fluorinated samples showed that fluorine concentration profile in depth is thinner in the in-line fluorinated sample when compared with the post-mould fluorinated sample, though the fluorination degree in the extreme surface is larger in the in-line fluorinated sample. This is attributed to a migration of lower surface energy chain blocks towards the surface in the material at high temperatures, which is the case in the in-line fluorination, hindered in the post-mould fluorination where maximum temperature is below the melting point to keep the macroscopic shape. The additives played a minor role in the ability of the surface to be fluorinated. 相似文献
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AbstractTwo waterborne poly(meth)acrylates containing fluorinated side chains (PALF and PASF) were synthesized by conventional radical copolymerization. Then waterborne epoxy composites with hydrophobic surface were obtained through a phase-inversion emulsion technique, using the PALF and PASF acrylates as reactive surface additives. Contact angle measurements and X-ray photoelectron spectroscope were employed to characterize the surface properties and the results confirmed that the fluorine atoms in the longer fluorinated side chains migrated to the outmost layer more efficiently. The effect of the fluorinated content and the length of the fluorine side chain on thermal and bulk properties of the waterborne epoxy resin was investigated. With increasing the fluorinated content or the length of the fluorine side chain, the contact angles and thermal properties improved while the mechanical properties showed no deterioration. 相似文献
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The effects of host/filler interactions, processing, and morphological development of low percolation threshold (Φc) conducting blends were investigated. It was found that the value of Φc was dramatically reduced by the isolation of the carbon black (CB) conducting filler at the cocontinuous interface of a binary poly(styrene) (PS) and poly(styrene co‐acrylonitrile) (SAN) insulating host, resulting in a multiple percolation effect. Accumulation of the filler at the interface was possible due to the incompatibility of the CB filler with the PS phase and partial compatibility with the SAN phase. The best results were obtained by initially dispersing the CB in the PS phase during melt‐ blending, followed by the addition of the SAN phase. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3106–3119, 2000 相似文献
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L. Jong 《Journal of Polymer Science.Polymer Physics》2005,43(24):3503-3518
Both linear and nonlinear viscoelastic properties of ionic polymer composites reinforced by soy protein isolate (SPI) were studied. Viscoelastic properties were related to the aggregate structure of fillers. The aggregate structure of SPI is consisted of submicron size of globule protein particles that form an open aggregate structure. SPI and carbon black (CB) aggregates characterized by scanning electron microscope and particle size analyzer indicate that CB aggregates have a smaller primary particle and aggregate size than SPI aggregates, but the SPI composites have a slightly greater elastic modulus in the linear viscoelastic region than the CB composites. The composite containing 3–40 wt % of SPI has a transition in the shear elastic modulus between 6 and 8 vol % filler, indicating a percolation threshold. CB composites also showed a modulus transition at <6 vol %. The change of fractional free volume with filler concentration as estimated from WLF fit of frequency shift factor also supports the existence of a percolation threshold. Nonlinear viscoelastic properties of filler, matrix, and composites suggested that the filler‐immobilized rubber network generated a G′ maximum in the modulus‐strain curves and the SPI formed a stronger filler network than the CB in these composites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3503–3518, 2005 相似文献