Effects of polymer-filler interactions on controlling the conductive network formation in polyamide 6/multi-Walled carbon nanotube composites

• Published in: Polymer (Guilford) 2019-09, Vol.178, p.121684, Article 121684
• Main Authors: Kazemi, Yasamin, Kakroodi, Adel Ramezani, Mark, Lun Howe, Filleter, Tobin, Park, Chul B.
• Format: Article
• Language: English
• Subjects: Calorimetry; Carbon nanotubes; Conduction; Contact resistance; Crystals; Differential scanning calorimetry; Elections; Electric contacts; Electrical conductivity; Electrical properties; Electrical resistivity; Electron tunneling; Microscopy; Morphological control; Multi wall carbon nanotubes; Nanocomposites; Network formation; Percolation; Polyamide resins; Polyamides; Polymer matrix composites; Polymers; Rheological properties; Transcrystalline layers; X-ray diffraction
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2019.121684

This study reports on the effects of polymer-filler interactions, in particular transcrystallization, on controlling the conductive network formation in polyamide 6 (PA6)/multiwalled carbon nanotube (MWCNT) composites. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results show that MWCNTs act as strong heterogeneous nucleating agents for PA6 crystals. Transmission election microscopy (TEM) confirmed the formation of a thick transcrystalline layer on the surfaces of the MWCNTs in PA6/MWCNT composites. Consequently, electrical conductivity measurements revealed that the formation of heterogeneously nucleated PA6 transcrystalline layers on the MWCNTs’ surfaces disrupt direct contact between adjacent MWCNTs and impeded the insulating-to-conductive transition in PA6/MWCNT composites. Thus, the electrical percolation threshold was observed at much higher MWCNT content as compared to the rheological percolation threshold. Interestingly, the current-voltage (I–V) characterizations showed that even at a high MWCNT content of 10 wt%, electron tunneling was the dominant electron conduction mechanism, signifying the lack of direct contact between the adjacent MWCNTs in the PA6/MWCNT composites. [Display omitted] •MWCNTs act as strong heterogeneous nucleating agents for PA6 crystals.•Heterogeneously nucleated crystals disrupt direct contact between adjacent MWCNTs.•Tunneling was the dominant mechanism of electron conduction in PA6/MWCNT composites.