Positive-temperature-coefficient effect of electrical resistivity below melting point of poly(vinylidene fluoride) (PVDF) in Ni particle-dispersed PVDF composites

• Published in: Polymer (Guilford) 2012-04, Vol.53 (8), p.1760-1764
• Main Authors: Kono, Akihiko, Shimizu, Katsuya, Nakano, Hajime, Goto, Yousuke, Kobayashi, Yusuke, Ougizawa, Toshiaki, Horibe, Hideo
• Format: Article
• Language: English
• Subjects: Applied sciences; Composites; electrical resistance; Exact sciences and technology; Forms of application and semi-finished materials; melting; melting point; Particle-dispersed conductive polymer composites; Poly(vinylidene fluoride); Polymer industry, paints, wood; polymers; Positive-temperature-coefficient effect; Technology of polymers; temperature
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2012.02.048

This paper discusses the positive-temperature-coefficient effects of resistivity in Ni particle-dispersed poly(vinylidene fluoride) (PVDF) composites based on experiment results from SEM, DSC, and pressure-volume-temperature (PVT) measurements. The melting points of composites with Ni content of 20, 30, 40, and 50vol.% were equal to that of pure PVDF. The PTC effects in composites with Ni content of 40 and 50vol.% occurred at temperatures near the melting point of the PVDF matrix, whereas those in composites with Ni content of 20 and 30vol.% occurred at temperatures below the melting point of the PVDF matrix. We found that the PTC effect occurs even without melting of the matrix polymer. Moreover, we determined that a slight increase in specific volume at temperatures below the melting point of the matrix polymer acts fully as a driving force for forming a gap between fillers. This suggestion was backed up by theoretical analyses using percolation theory and a thermal-fluctuation-induced tunneling model. [Display omitted]