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Thermal diffusivity and conductivity measurements of polymer nanocomposites


U. Gross1, A. Fina2 and M. Mainil3

1TU Bergakademie Freiberg, Institute of Thermal Engineering, Germany
2Politecnico di Torino – Sede di Alessandria, Italy
3NANOCYL S.A., R&D Department, Sambreville, Belgium

Keywords: polymer nanocomposites
property: thermal conductivity, thermal diffusivity
material: polymer, carbon nanotubes, graphite

Thermally conductive polymer composites offer new possibilities for replacing metal parts in several applications, including power electronics, electric motors and generators, heat exchangers etc., thanks to the polymer advantages such as light weight, corrosion resistance and ease of processing. Current interest to improve the thermal conductivity of polymers is focused on the selective addition of fillers with high thermal conductivity. However, the thermal conductivities of polymer composites are relatively low compared with expectations from the intrinsic thermal conductivity of the conductive particles. The challenge primarily comes from the large thermal resistance between the particle/particle and particle/polymer interfaces, which hinders the heat transfer through the material [1]. The strict control of the composite structure, in terms of conductive particle dispersion and distribution, is thus needed to maximise the efficiency of thermal contact between the particles.

In this work, different approaches have been explored to maximise the thermal conductivity of thermoplastic polymers (polypropylene, polyvynilidene fluoride) containing conductive particles (graphite, carbon nanotubes), including i) optimization of mixing conditions, ii) combination of conductive particles with different geometries and/or with cofillers to improve dispersion, iii) controlled segregation of conductive particles in double-percolated immiscible polymer blends [2].

Thermal diffusivity was measured by the Laser flash method, for the thermal conductivity a modified Despretz method was applied.

Encouraging results were obtained for the double-percolated blends, clearly showing better thermal conductivity compared with single polymer composites containing the same graphite loadings.

References
  1. Z. Han, A. Fina, Prog. Polym. Sci. (2011), doi:10.1016/j.progpolymsci.2010.11.004

  2. A. Fina, Z. Han, U. Gross, M. Mainil, Submitted to European Polymer Journal

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