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Unified modeling and experimental realization of electrical and thermal percolation in polymer composites

Sarikhani, N ; Sharif University of Technology | 2022

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  1. Type of Document: Article
  2. DOI: 10.1063/5.0089445
  3. Publisher: American Institute of Physics Inc , 2022
  4. Abstract:
  5. Correlations between electrical and thermal conduction in polymer composites are blurred due to the complex contribution of charge and heat carriers at the nanoscale junctions of filler particles. Conflicting reports on the lack or existence of thermal percolation in polymer composites have made it the subject of great controversy for decades. Here, we develop a generalized percolation framework that describes both electrical and thermal conductivity within a remarkably wide range of filler-to-matrix conductivity ratios (Y f / Y m), covering 20 orders of magnitude. Our unified theory provides a genuine classification of electrical conductivity with typical Y f / Y m ≥ 10 10 as insulator-conductor percolation with the standard power-law behavior and of thermal conductivity with 10 2 ≤ Y f / Y m ≤ 10 4 as poor-good conductor percolation characterized by two universal critical exponents. Experimental verification of the universal and unified features of our theoretical framework is conducted by constructing a 3D segregated and well-extended network of multiwalled carbon nanotubes in polypropylene as a model polymer matrix under a carefully designed fabrication method. We study the evolution of the electrical and thermal conductivity in our fabricated composites at different loading levels up to 5 vol. %. Significantly, we find an ultralow electrical percolation threshold at 0.02 vol. % and a record-low thermal percolation threshold at 1.5 vol. %. We also apply our theoretical model to a number of 23 independent experimental and numerical datasets reported in the literature, including more than 350 data points, for systems with different microscopic details, and show that all collapse onto our proposed universal scaling function, which depends only on dimensionality. © 2022 Author(s)
  6. Keywords:
  7. Filled polymers ; Fillers ; Matrix algebra ; Multiwalled carbon nanotubes (MWCN) ; Percolation (computer storage) ; Percolation (fluids) ; Polymer matrix composites ; Solvents ; Yarn ; Electrical conduction ; Electrical percolation ; Experimental realizations ; Filler particles ; Heat carriers ; Nanoscale junctions ; Polymer composite ; Thermal conduction ; Thermal percolation ; Unified Modeling ; Polypropylenes
  8. Source: Applied Physics Reviews ; Volume 9, Issue 4 , 2022 ; 19319401 (ISSN)
  9. URL: https://aip.scitation.org/doi/10.1063/5.0089445