Resistance-temperature Effect Of Conductive Polymer Composites With Special Morphology

Conductive polymer composites exhibited excellent positive temperature effect (PTC effect) only when conductive filler concentration was a little bit higher than the percolation threshold. In this paper, for the composites with conductive filler concentration far higher than the percolation threshold, controlling the dispersion of conductive filler at the interface and the morphology of blends was employed to prepare composites with excellent PTC effect.Carbon black (CB) or carbon nanotubes (CNTs) were chosen as conductive particles, poly(ethylene-co-butyl acrylate)/nylon6(EBA/PA6) or polystyrene/nylon6(PS/PA6) were employed as immiscible polymer blends. The method that conductive particles were first reacted with compatibilizer and then melting blended with immiscible polymer blends, has been employed to prepare the composites of which conductive particles localized at the interface. The localization of conductive particles at the interface can decrease percolation threshold greatly. The conductive performance of composites with different types of morphology was studied. And the results showed composites with co-continuous and sea-island morphology both exhibited good conductive performance. In addition, corresponding conduction models were suggested to explain those phenomena. For composites with conductive filler concentration far higher than the percolation threshold, the influence of different types of morphology on resistance-temperature behavior of composites was studied. The results showed that conductive filler should form complex conductive network constructed at the interface and in PA6phase near the interface when conductive filler concentration was far higher than the percolation threshold. For composites with sea-island morphology in which PA6phase formed dispersed phase, the phase transition of the continuous phase caused the interrupt of conductive network formed in and near interface, resulting in the appearance of PTC effect. Meanwhile, the melt of PA6phase caused the negative temperature-coefficient effect (NTC). As the decrease of PA6content, the PTC effect caused by the phase transition of the continuous phase appeared at lower temperature. Comparing with the composites with conductive filler concentration a bit higher than the percolation threshold, composites with conductive filler concentration for higher than the percolation threshold exhibited higher PTC intensity, and PTC effect appeared at lower temperature. For composites with sea-island morphology in which PA6phase formed continuous phase, the phase transition of the dispersed phase exhibited a weak effect on their resistance-temperature behavior. However, the phase transition of continuous PA6phase caused the resistance-temperature effect. The increase of conductive particles content should weaken resistance-temperature effect. For CB filled blends with co-continuous morphology. PTC effect was observed at the phase transition temperature of the matrix. The increase of CB particles content reinforced resistance-temperature effect. For CNTs filled blends with co-continuous morphology. PTC effect was observed at the melting temperature of PA6phase. Meanwhile, the increase of CNTs particles content weakened their resistance-temperature effect.