EFFECTIVE THERMAL-CONDUCTIVITY OF A LOW-DENSITY POLYETHYLENE AND IONIC SALTS COMPOSITE

The effective thermal conductivity lambda(e) of model dispersed composites prepared from well specified powders of NaF and low-density polyethylene (LDPE) was measured at different volume fractions at temperatures in the range 120-320 K and pressures up to 1.73 GPa. Measurements were made using the hot-wire technique. The ratio of thermal conductivities of NaF and LDPE reached values up to 60 at the temperatures and pressures employed. These results together with the previous data on AgCl-LDPE and NaCl-LDPE composites were used for testing the extensive set of theoretical models which permit us to calculate lambda(e) in the wide range of volume concentrations and component conductivity ratios. We have come to the conclusion that at low concentrations of the more conductive component the bond lattice model describes the experimental data better then site lattice model, and at high concentrations the situation is the opposite. The best single model for all data is the ''renormalized effective medium approximation'' model of Sahimi which brings together effective medium and renormalization group approaches.