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 (10μm, 50μm and 150μm). With increasing particle content thermal diffusivity arises from α(PU + 0% Fe₃O₄) ≈ 0.13mm²/s to α(PU + 40% Fe₃O₄) ≈ 0.31mm²/s whereas d = 10μm particle sizes lead to higher values than larger particle sizes. Values measured for 150μm large particles are lying between values of composites with 10μm and 50μm 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 λ(PU+0% Fe₃O₄) ≈ 0.2W/mK to λ(PU+40% Fe₃O₄) ≈ 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.