کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1523805 | 995330 | 2012 | 9 صفحه PDF | دانلود رایگان |
Different relative density polypropylene foams were prepared by means of two foaming processes: chemical foaming by compression moulding and physical foaming by high pressure CO2 dissolution. By controlling the foaming parameters, such as blowing agent concentration, foaming temperature, pressure drop and pressure drop rate, it was possible to regulate the cellular structure, foams showing from markedly isotropic-like cellular structures to ones with highly-elongated cells in the vertical foam growth direction (honeycomb-like cell orientation). The thermal conductivity was measured using the transient plane source method. Using this technique, it was possible to measure the global conductivity and the thermal conductivity in both the axial and radial directions of a given sample. Results show that the global thermal conductivity of foams was mainly regulated by their relative density. In addition, the honeycomb-like cell orientation of the CO2 dissolution foams resulted in considerably higher values in axial direction when compared to radial, demonstrating that there was a direct influence of cellular structure on the thermal conduction behaviour of these foams, enabling the development of new polypropylene foams with direction-dependent thermal properties.
► We study the thermal anisotropy of polypropylene foams using a transient method.
► Cellular structure influences the thermal conductivity of CO2 dissolution foams.
► Thermal anisotropy increases with reducing density due to a stretched cell structure.
► The lowest density CO2 dissolution foams show axial conductivity similar to solid PP.
► By separating axial and radial components we show the importance of cell orientation.
Journal: Materials Chemistry and Physics - Volume 136, Issue 1, 14 September 2012, Pages 268–276