THERMAL PROPERTIES OF POLYURETHANE SHAPE MEMORY POLYMER FILLED WITH MAGNETITE PARTICLES

Temperature dependent thermal diffusivity (295K <= T <= 375K), specific heat capacity (290K <= T <= 380K) and thermal conductivity (300K <= T <= 340K) were measured on extrusion compounded and injection molded polyurethane shape memory polymers filled with different volume fractions (0%, 10%, 20%, 30%, 40%) of magnetite particles (10 mu m, 50 mu m and 150 mu m). With increasing particle content thermal diffusivity arises from a(PU + 0%Fe3O4) approximate to 0.13mm(2) /s to alpha(PU + 40%Fe3O4) approximate to 0.31mm(2)/s whereas d=10 mu m particle sizes lead to higher values than larger particle sizes. Values measured for 150 mu m large particles are lying between values of composites with 10 mu m and 50 mu m particle sizes in the whole investigated temperature range. For higher filler contents differences in thermal diffusivity between composites of different particle sizes disappear Thermal diffusivity decreases with increasing temperature, while thermal conductivity is increasing from lambda(PU+0%Fe3O4)approximate to 0.2W/mK to lambda(PU+40%Fe3O4)approximate to 0.6W/mK. Corresponding to glass transition temperatures of the polymer the specific heat capacity shows a rise between 300K and 320K and a decrease between 350K and 370K.