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The influence of different hosts, processing conditions and conducting fillers on the percolation threshold (Φc) of the resulting conducting blends was investigated. Results indicate that microscopic properties, such as the dipole moments of the side‐groups, and distribution of these groups on the host polymer backbone govern the strength of host–filler interactions, and to a large extent, the value of Φc, rather than macroscopic properties such as surface tension. The grade of carbon black used in this experiment was found to be polar in nature and it resulted in lower values of Φc with the polar hosts, contrary to published literature. In general, melt blending has been shown to result in higher values of Φc when compared to hot pressing alone. In the latter method the conductive filler was found to be isolated at the grain boundaries of the polymer host, resulting in the formation of continuous conducting pathways at low filler concentration. © 2001 Society of Chemical Industry 相似文献
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The electrical resistivity and thermal conductivity of a liquid crystalline polymer (LCP) filled with a commercial carbon black (CB) of various volume fractions (?) is investigated. The percolation threshold (?c) is found at about 3%, and the resistivity (ρ) as a function of (? ? ?c) satisfies the exponential function. Although the pure LCP is highly anisotropic in thermal and mechanical properties after processing, the composite samples exhibit no preferential direction for electrical conduction. Samples of ? below ?c exhibit a negative temperature coefficient of resistivity while those above ?c show almost no temperature dependence from room temperature to 200°C. In addition, the samples at lower ? have higher thermal conductivity in the LCP flow direction than those measured in the transverse and thickness directions, and they approach the same value at higher ?. This result indicates that preferential molecular alignment of the matrix LCP is responsible for the behavior of the thermal conductivity of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1549–1555, 2001 相似文献
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For green tires, carbon black (CB) is partially replaced by silica (SiO2) in the tread formula in order to improve wet grip (WG) and fuel saving efficiency (FSE). However, such replacement inversely affects electrical conductivity of a tire resulting a greater potential for static shock or electrostatic ignition. This work aimed to improve electrical conductivity of the tread compound by partially replacing either CB or SiO2 by 0–12 phr of conductive carbon black (CCB) (with replacing ratio of 2:1) and investigating the effect of such replacement on the tire performance. Although the partial replacement of CB or SiO2 by CCB increased the magnitude of transient filler network resulting in the negative effects on heat build-up, WG and FSE of the tread vulcanizates, it significantly improved electrical conductivity. Surface resistivity decreased sharply when CB or SiO2 was replaced by 3 phr of CCB, revealing the point of percolation threshold. In addition, the partial replacement of CB or SiO2 by CCB did not cause significantly change of both hardness and tensile properties. At any given CCB loading, the SiO2 replacement provided greater surface conductivity and higher abrasion resistance with lower WG and FSE than the CB replacement. 相似文献
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炭黑/环氧树脂复合材料导电行为的研究 总被引:3,自引:2,他引:1
分别采用不同的混合分散方法制备炭黑/环氧树脂(CB/EP)复合材料(CB牌号为F101、XE2,EP牌号为E-54、E-51和E-44),研究了制备工艺、CB用量和CB结构等对复合材料导电性能的影响。结果表明:不同方法制得的复合材料体积电阻率的大小依次为机械混炼法离心混合法超声分散法;CB/EP复合材料的导电性能随CB用量增加而显著提高,并且F101/E-54、XE2/E-54复合材料体系均表现出明显的导电渗流行为;CB结构对复合材料的导电性能影响较大,F101/E-54、XE2/E-54复合材料体系的导电渗流阈值分别为3.85%、0.47%。 相似文献
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2种导电炭黑复合橡胶体系的导热性能研究 总被引:2,自引:0,他引:2
研究了2种导电炭黑复合天然橡胶材料的导热性能随着温度和填料用量的变化规律。结果表明,温度对于导电炭黑复合体系导热性能的影响不大。乙炔黑复合体系具有极高的导热性能,随着炭黑用量的增加,其导热性能优势越加明显。据透射电镜观察填料的微观形态,乙炔黑链枝状结构丰富,聚集体之间以面接触为主,这是其复合橡胶导热性能优异的原因,乙炔黑复合材料的热导率与炭黑体积分数呈线性关系。40B2复合体系的热导率与炭黑体积分数呈现逾渗规律,逾渗阈值在炭黑体积分数8.30%至13.63%之间。据扫描电镜观察复合材料的微观结构,逾渗现象与炭黑在基体内的分布密切相关。为更精确地描述填料用量与复合体系热导率的关系,对2种复合体系的热导率与炭黑的体积分数进行了回归。 相似文献
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Two different types of surface modifiers, 3‐aminopropyltriethoxysilane and formamide, were applied to carbon black (CB) particles to lower electrical resistivity of polymer composites prepared by treated CB. Two different matrices, low‐density polyethylene and nylon 6, were chosen to compound with surface modified CB. Surface energy of CB was increased by adding amine or amide functional groups during surface treatment of CB. According to electron spectroscopy for chemical analysis (ESCA), chemical modification in surface chemistry of CB was obtained with the chemicals used for the treatment due to the nitrogen atoms in their structures, which may act as dopant atom. As a result of this, electrical resistivity of composites prepared by treated CB decreased. In addition, there was not any significant change in tensile strength and tensile modulus of the composites with the surface treatment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
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Matthias-Klaus SchwarzKarl Schulte 《Polymer》2002,43(10):3079-3082
This letter reports on our observation that an alternating electric field is able to induce the formation of an electrically conducting network in carbon black (CB) filled resins well below the zero-field percolation threshold. Compared with the recently presented dc method, the ac agglomeration is more efficient in two respects: it proceeds significantly faster under equivalent conditions and is still effective at higher ionic concentration. In contrast to the ramified form of dc-induced CB networks, ac agglomeration favors the formation of parallel CB chains. The experimental results can be explained taking into account ionic conductivities of the matrices as well as charges and field induced dipoles on the CB particles. 相似文献
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The polyurethane composites with conducting carbon black (CB) were prepared by a solution‐precipitation process, which was followed by melt compression molding. The polyurethane used has good shape memory effect. The morphology of CB fillers in polyurethane matrix and the resulting conductivity of the composites were investigated. It has been found that CB fillers exist in the forms of aggregates. The percolation threshold is achieved at the CB concentration of 20 wt %. The presence of CB fillers decreases the degree of crystallinity of polycaprolactone (PCL) soft segments of the polyurethane. However, the composites still have enough soft‐segment crystals of polyurethane to fulfil the necessary condition for the shape memory properties. Dynamic mechanical data show that CB is an effective filler for the reinforcement of the polyurethane matrix, but does not deteriorate the stable physical cross‐link structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory materials. Addition of CB reinforcement in the polyurethane has influenced the strain recovery properties, especially for those samples with CB concentrations above the percolation threshold. The response temperature of the shape memory effect Tr has not been affected too much. Strain fixation Sf, which expresses the ability of the specimens to fix their strain, has been improved in the presence of the CB fillers. The final recovery rates Rf and strain recovery speeds Vr of the shape memory measurements, however, have decreased evidently. It is expectedly ascribed to the increased bulk viscosity as well as the impeding effect of the inter‐connective structure of CB fillers in the polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 68–77, 2000 相似文献
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Room temperature resistance relaxation was studied with respect to carbon black (CB) volume fraction, the type of polymer matrix, and the environment. It was found that resistance of CB filled poly(methylvinylsiloxane) and polypropylene (PP) conductive composites changed at room temperature with different directions and amplitudes, depending on the filler volume fraction and the environment. The room temperature resistance relaxation was ascribed to the local Joule heat at the tunneling junction or the swelling effect of the solvents. On the other hand, CB filled immiscible PP/Nylon 1212 blends exhibited a stable electrical conduction due to the selective distribution of CB aggregates along the interface between polymer matrices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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Dispersing conductive carbon black (CCB) particles into silicone rubber (SR), we studied the conductivity and piezoresistivity of particles filled polymer composite. The experimental results show that the conductive percolation threshold and shape exponent of composite are effected on by filler's size and reduce with filler's size decreasing. The electrical resistance and Young's model of composite have different critical filler volume fraction to fall or increase. The compressing deformation is the main reason of the piezoresistivity of composite, but the piezoresistivity is more obvious when particles have larger size or polymer matrix has smaller Young's Model. A research was done to explain the piezoresistivity through comparing CCB/SR with CCB/high density polythene (HDP). The other interesting find is that the electrical resistance of composite decreases with time under an invariant load, showing “electrical resistance creep” behavior, which is due to the composite's compressing strain creep under uniaxial pressure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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The morphology and electrical properties of linear low density polyethylene (LLDPE)/poly (ethylene‐methyl arylate) (EMA) blends filled with carbon black (CB) are investigated in this work. Comparing to LLDPE/CB composite, the higher percolation threshold of EMA/CB composite is attributed to the good interaction between EMA and CB. However, carbon black is found to locate preferentially in the LLDPE phase of LLDPE/EMA immiscible blends from the characterization of SEM and electrical properties, which greatly decreases the percolation threshold of the composites. The viscosity of the two polymers is the key factor to determine the distribution of CB instead of interfacial energy in this system. This suggests a method to control the distribution of CB in the immiscible blends by choosing the viscosity ratio of polymer blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 487–492, 2007 相似文献
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Dispersion of fillers and the electrical conductivity of polymer blends filled with carbon black 总被引:2,自引:1,他引:1
Masao Sumita Kazuya Sakata Shigeo Asai Keizo Miyasaka Hideaki Nakagawa 《Polymer Bulletin》1991,25(2):265-271
Dispersion state of carbon black(CB) was studied in polymer blends which are incompatible with each other. It was found that CB distributes unevenly in each component of the polymer blend. There are two types of distribution. (1) One is almost predominantly distributed in one phase of the blend matrix, and in this phase fillers are relatively homogeneously distributed in the same manner as a single polymer composite. (2) In the second, the filler distribution concentrates at interface of two polymers. As long as the viscosities of two polymers are comparable, interfacial energy is the main factor determining uneven distribution of fillers in polymer blend matrices. This heterogeneous dispersion of conductive fillers has much effect on the electrical conductivity of CB filled polymer blends. The electrical conductivity of CB filled polymer blends is determined by two factors. One is concentration of CB in the filler rich phase and the other is phase continuity of this phase. These double percolations affect conductivity of conductive particle filled polymer blends. 相似文献
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In the current study, polylactic acid/high density polyethylene/carbon black (PLA/HDPE/CB) composites are prepared via a two-step method. A double percolation network with co-continuous structure and filler distribution at the interface is constructed to design conductive polymer composites with low percolation threshold. The controllable distribution of CB at the interface is achieved by appropriate processing procedures involved mixing sequence and mixing time by taking advantage of the migration of CB from the unfavorable PLA phase to the favorable HDPE phase. Morphology characterization reveals that when the mixing time of the added HDPE is 3 min, the formation of co-continuous structure of PLA/HDPE (60/40, w/w) is observed, and CB particles migrate to the co-continuous interface. The electrical conductivity measurement shows that such double percolation conductive network reduces the percolation threshold of PLA/HDPE/CB to 2.42 wt%. The rheological property proves the establishment of particle percolation network, and the rheological percolation threshold is determined as 1.20 wt%. The prepared PLA/HDPE/CB composite by the two-step method displays a notably low percolation threshold than that prepared by one-step simultaneous mixing. Moreover, this strategy presents a high potential application in the fabrication of conductive polymer composites involving other miscible multiphase systems. 相似文献
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The co-continuous morphology of polymer blends has received much attention not only because of its potential promotion of mechanical or electrical properties of polymer blends, but also due to its importance in phase separation by spinodal decomposition. Compared to the recent advances in the characterization of co-continuous structure, the rheology of co-continuous blends has not been understood clearly. In this work, a rheological model is suggested to correlate the linear viscoelasticity and the structural information of co-continuous blends. The dynamic modulus of co-continuous blends is composed of the contribution from components and the interface. The interfacial contribution, which is most important in the rheology of blends, is calculated from a simplified co-continuous structure. This model has been compared satisfactorily with available experimental results, which proves a reasonable connection between the co-continuous structure and linear viscoelasticity of blends. 相似文献
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