Preparation and photothermal characterization of nanocomposites based on high density polyethylene filled with expanded and unexpanded graphite: Particle size and shape effects

Chirtoc M., Horny N., Tavman I., TURGUT A., Kokey I., Omastova M.

INTERNATIONAL JOURNAL OF THERMAL SCIENCES, vol.62, pp.50-55, 2012 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 62
  • Publication Date: 2012
  • Doi Number: 10.1016/j.ijthermalsci.2012.02.015
  • Journal Name: INTERNATIONAL JOURNAL OF THERMAL SCIENCES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.50-55
  • Keywords: Nanocomposites, HDPE, Expanded graphite, Photothermal radiometry, Thermal conductivity, Effective medium approximation
  • Dokuz Eylül University Affiliated: Yes

Abstract

This work aimed at thermal transport characterization of high density polyethylene (HDPE) filled with 5 and 50 mu m expanded graphite (EG) particles and with 0.4 mu m unexpanded graphite (UG) particles. Sample platelets were produced by melt mixing followed by compression molding. Thermal conductivity k was determined by combining measurements of density, specific heat capacity and thermal diffusivity, the latter by modulated photothermal radiometry (PTR). Starting from an effective medium approximation model, we derived a linearized expression for the effective k of composites with low particle charge. It explains the unusually high experimental k values (up to four-fold increase) as the effect of strongly non-spherical EG particles (aspect ratio 1/p = 110-290). Larger particle sizes produce higher k enhancement, while the interfacial thermal resistance (R-bd = 21.10(-7) m(2).K/W) has an opposite effect. The same model is consistent with experimental k for low particle charge HDPE/UG composites. At higher particle charge the model fails due to particle interaction leading to validity break of the effective medium approximation. (C) 2012 Elsevier Masson SAS. All rights reserved.