Photothermal Characterization of Nanocomposites Based on High Density Polyethylene (HDPE) Filled with Expanded Graphite
INTERNATIONAL JOURNAL OF THERMOPHYSICS, vol.33, pp.2110-2117, 2012 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 33
- Publication Date: 2012
- Doi Number: 10.1007/s10765-012-1305-y
- Journal Name: INTERNATIONAL JOURNAL OF THERMOPHYSICS
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Page Numbers: pp.2110-2117
- Keywords: Expanded graphite, Flash IR thermography, HDPE, Heat capacity, Nanocomposites, Optical absorption coefficient, Photothermal radiometry, Thermal diffusivity, Thermal effusivity
- Dokuz Eylül University Affiliated: Yes
Abstract
The effective thermophysical and optical properties of high density polyethylene (HDPE) filled with 50 mu m and 5 mu m particle sizes of expanded graphite (EG50, EG5) are characterized. The methods used were front- and back-detection modulated photothermal radiometry (FD-, BD-PTR) and BD-flash IR thermography. Results were interpreted according to one-dimensional heat diffusion models. The absolute thermal diffusivity was determined at low frequency from FD- and BD-PTR spectra, while the volumetric heat capacity, the thermal effusivity, and the optical absorption coefficient were determined from broad-band FD-PTR spectra. The directly obtained diffusivity values compare well with those calculated from the heat capacity and thermal effusivity, and with BD-flash results. The errors caused by the finite absorption coefficient of diluted samples are also evaluated and corrected for. A particle-size effect with the opposite influence on thermal and optical properties has been observed. Heat transport parameters of HDPE/EG composites are significantly enhanced (factor of 3 to 4 in thermal diffusivity) at low particle charge before reaching saturation above a 0.10 particle volume fraction. These features are explained in the framework of effective medium models by strongly non-spherical EG particles.