Thermo-resistive and thermo-piezoresistive sensitivity of carbon nanostructure engineered thermoplastic composites processed via additive manufacturing

Verma, P., Schiffer, A. and Kumar, S. (2021) Thermo-resistive and thermo-piezoresistive sensitivity of carbon nanostructure engineered thermoplastic composites processed via additive manufacturing. Polymer Testing, 93, 106961. (doi: 10.1016/j.polymertesting.2020.106961)

Abstract

We experimentally examine the thermo-resistive and thermo-piezoresistive sensitivity of multiwall carbon nanotube (MWCNT)/polypropylene random copolymer (PPR) nanocomposites processed via fused filament fabrication (FFF) process. The filament feedstocks were fabricated by melt blending of neat PPR with a predetermined amount of MWCNTs (either 4, 6 or 8 wt.%) using a twin-screw extruder. Thermo-resistive characteristics of MWCNT/PPR composites were measured under both constrained and unconstrained heating from approximately 30-100°C. For all MWCNT concentrations considered here, negative temperature coefficients of resistivity (TCR) were observed for both constrained and unconstrained heating, as a consequence of thermal fluctuation-induced tunneling at MWCNT junctions. The highest thermo-resistive sensitivity was measured for the composite with the lowest MWCNT concentration (4 wt.%) under unconstrained conditions, reporting a TCR of -12,800×10-6/°C, which is higher in magnitude than that of other polymer nanocomposites reported in the literature. Moreover, the MWCNT/PPR composites exhibit strong thermo-piezoresistive response under tensile loading. For 4 wt.% MWCNT loading, the gauge factor (measured over 0-20% strain range) of the composite increased from 27.8 to 52.3 when the temperature was raised from 30°C to 60°C. Our results further evince higher thermo-piezoresistive sensitivity i.e., a gauge factor as high as 395 at 600C. The electron tunneling and hopping, both thermally-assisted and activated by mechanical deformation of the PPR matrix, significantly increase the thermo-piezoresistance with the increase in temperature in this range. The excellent thermo-resistive and thermo-piezoresistive characteristics of MWCNT/PPR composites reported in this study would enable the development of smart nanocomposites for self-sensing both temperature and strain/damage state.

• Item Type: Articles
• Additional Information: Authors would like to thank Abu Dhabi National Oil Company (ADNOC) for providing the research grant (Award No: EX2016-000010). SK would like to the University of Glasgow for the start-up grant.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kumar, Professor Shanmugam
• Authors: Verma, P., Schiffer, A., and Kumar, S.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: Polymer Testing
• Publisher: Elsevier
• ISSN: 0142-9418
• ISSN (Online): 1873-2348
• Published Online: 18 November 2020
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in Polymer Testing 93: 106961
• Publisher Policy: Reproduced under a Creative Commons License