Significant Ultra-low Percolation Threshold, Enhanced Positive Temperature Coefficient Effect and Dielectric Permittivit
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Significant ultra-low percolation threshold, enhanced positive temperature coefficient effect and dielectric permittivity in polymer-based composites with immiscible polymers H. P. Xu1, N. C. Bing1, Y. H. Wu1, D. D. Yang1 and Z. M. Dang2 1 School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209, PR China 2 Key Laboratory of Beijing City for Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029, PR China ABSTRACT Significant conductive polymer-based composites consisting of immiscible semi-crystalline polymers PP and PVDF, at different volume ratios loaded with a certain concentration of CB were prepared by blending and sequent hot-pressing technology. The distributing status of CB in the polymers was evaluated through the micrographs of the composite. The percolation threshold of this kind of composite is much lower than those of the individual polymers. Even more, the composite at 1/1 volume ratio of PP and PVDF displays the best conductivity among different ratios at a certain concentration of CB, and it displays an outstanding PTC effect more than five orders of magnitude, and synchronously an enhanced dielectric permittivity about 24.9 at 100 Hz. These inimitable properties may owe to the formation of PP/PVDF co-continuous phases and a double-percolation effect in the composite. The novel polymer-based composite with ultra-low percolation threshold, enhanced PTC effect, as well as the significant dielectric permittivity is promising a potential application.
INTRODUCTION Polymer composites have attracted much interest due to their excellent mechanical, physical and thermal properties, as well as excellent formability, flexibility and lightweight [1-3]. Conductive particles filled semi-crystalline polymer composites usually exhibit inimitable important insulator–conductor transitions, significant positive temperature coefficient (PTC) effect or novel dielectric property when the filler content is close to the critical volume fraction referred as the “percolation threshold” [3,4]. Research and development activities in such composites, especially containing carbon black (CB) and a single semi-crystalline polymer have brought successful industrial applications in self-regulating heaters, over-current and overtemperature protection devices, and dielectric materials applied in capacitors [5,6]. Very recently, distributing of conductive fillers in immiscible semi-crystalline polymer composites have aroused much interest, which can lead to further improvement of conductive polymers in terms of both conductivity and mechanical properties [7]. However, there are some potential serviceable materials are far from empoldered. Furthermore, the significant dielectric behavior of such composite has seldom been investigated.
EXPERIMENT
Both of PP and PVDF were obtained from Shanghai 3F New Materials Ltd and Beijing Yanshan Petrochemical Ltd of China, respectively. The acetylene CB was provided b
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