Development of Ni particle dispersed poly(methylmethacrylate) composites exhibiting conductor/insulator transition by the positive temperature coefficient effect of electrical resistivity
Development of Ni particle dispersed poly(methylmethacrylate) composites exhibiting conductor/insulator transition by the positive temperature coefficient effect of electrical resistivity
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DOI：
10.1038/pj.2012.223
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发表时间：
2013-07
期刊：
影响因子：
2.8
通讯作者：
A. Kono;K. Shimizu;Hajime Nakano;Masashi Yamamoto;Yousuke Goto;Seiji Takahashi;T. Ougizawa;H. Horibe
中科院分区：
文献类型：
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作者：
A. Kono;K. Shimizu;Hajime Nakano;Masashi Yamamoto;Yousuke Goto;Seiji Takahashi;T. Ougizawa;H. Horibe
由结晶聚合物组成的复合材料的PTC效应可用以下模型来解释。几乎没有导电填料的纯聚合物的电阻率超过1012 OCM，而且这些聚合物的性能类似于绝缘体。当导电填料含量达到某一特定值时，复合材料的电阻率从绝缘范围突然下降到导电范围，这是因为导电填料以类似网络的形式连接在一起，形成了导电路径。一些金属颗粒较多的复合材料表现出10±2 OCM的低RL。8-10这些特征称为渗流现象。然而，即使有大量的导电填料，复合材料在基质聚合物熔点附近的电阻率也超过109OCM 8-10。这种电阻率变化是由于基质聚合物由于熔融而急剧体积膨胀后，导电路径断开所致。因此，许多由结晶型聚合物组成的复合材料表现出PTC效应。用上述模型解释了复合材料的PTC效应，从而假定由无定形聚合物组成的复合材料不表现出熔融现象，不表现出PTC效应。事实上，据报道，聚甲基丙烯酸甲酯(PMMA)/炭黑复合材料并没有表现出PTC效应，因为与晶态聚合物不同，非晶态聚合物不会表现出剧烈的体积膨胀。2此外，据报道，聚苯乙烯/炭黑复合材料的PTC强度仅为两位数。5在本研究中，我们研究了镍含量对镍颗粒分散PMMA复合材料PTC效应的影响。当Ni含量为20%和25%时，复合材料表现出PTC效应。此外，镍含量为25vol.%的复合材料的PTC强度达到108，相当于由结晶聚合物组成的复合材料的PTC强度。实验采用PMMA(HBS000，三菱人造丝，日本东京)、线性低密度聚乙烯(LLDPE：EVULE 3010，Prime Polmer，日本东京)和聚偏氟乙烯(PVDF：Kynar K720，Arkema，Columbe，法国)作为复合材料的基质聚合物。导电填料采用加拿大多伦多国际镍公司生产的镍粉。其平均粒径为2.5 mm，电阻率为710±5OCM。使用双辊混合器(4M150，Toyo Seiki，日本东京)在200 1C和60rpm的条件下熔融聚合物颗粒和镍颗粒15分钟。将复合材料插入两块钢板(150 mm×150 mm×2.2 mm)和
The PTC effect of composites composed of crystalline polymer is explained by the following model. The resistivity of almost pure polymer without conductive filler exceeds 1012 Ocm, and these polymers behave similar to insulators. When conductive filler content reaches a specific value, the resistivity of composites demonstrates a sudden decrease from insulating range to conducting range because the conductive filler is joined together similar to a network, forming a conductive path. Some composites with many metal particles exhibit a low rL of 10À2 Ocm. 8–10 These characteristics are known as the percolation phenomenon. 12–16 However, the resistivity of composites exceeds 109 Ocm 8–10 at near the melting point of the matrix polymer even with a large amount of conductive filler. This resistivity change is caused by a disconnection of conductive paths following the drastic volume expansion of matrix polymer due to melting. 2 Therefore, a number of composites composed of crystalline polymer exhibit the PTC effect. The PTC effect of composites was explained by the above models, and so it was assumed that composites composed of amorphous polymer, which do not exhibit the melting phenomenon, do not exhibit the PTC effect. In fact, it was reported that poly (methylmethacrylate)(PMMA)/carbon black composites do not demonstrate the PTC effect, because, unlike crystalline polymers, amorphous polymers do not exhibit drastic volume expansion. 2 Moreover, it was reported that the PTC intensity of polystyrene/carbon black composites is only in double digits. 5 In this study, we investigated the influence of Ni content on the PTC effect of Ni particle dispersed PMMA composites. Composites with Ni contents of 20 and 25 vol.% exhibited the PTC effect. Moreover, the PTC intensity of a composite with a Ni content of 25 vol.% reached 108, a value equivalent to that of composites composed of crystalline polymer.EXPERIMENTAL PROCEDURE PMMA (HBS000, Mitsubishi Rayon, Tokyo, Japan), linear low-density polyethylene (LLDPE: Evolue 3010, Prime Polymer, Tokyo, Japan) and poly (vinylidene fluoride)(PVDF: KYNAR K720, Arkema, Colombes, France) were used as a matrix polymer of the composites. Ni particles manufactured by Inco (Toronto, Canada) were used as the conductive filler. Its average particle size was 2.5 mm, and its resistivity was 7  10À5 Ocm. Polymer pellets and Ni particles were meltblended at 200 1C and 60 rpm for 15 min, using a two-roller mixer (4M150, Toyo Seiki, Tokyo, Japan). The composite was inserted between two steel boards (150mm 150 mm 2.2 mm) and