Abstract
In this study, a case study to produce microcellular foam of a commercial thermoplastic polyurethane (TPU) through the supercritical carbon dioxide (CO2) foaming process is presented. To explore the feasibility of TPU in medical device and biomedical application, a soft TPU with Shore hardness value of 70A was selected as the model compound. The effects of saturation temperature and saturation pressure ranging from 90 to 140 °C and 90 to 110 bar on the expansion ratio, cell size and cell density of the TPU foam were compared and discussed. Regarding the expansion ratio, the effect of saturation temperature was considerable and an intermediate saturation temperature of 100 °C was favorable to produce TPU microcellular foam with a high expansion ratio. On the other hand, the mean pore size and cell density of TPU foam can be efficiently manipulated by adjusting the saturation pressure. A high saturation pressure was beneficial to obtain TPU foam with small mean pore size and high cell density. This case study shows that the expansion ratio of TPU microcellular foam could be designed as high as 4.4. The cell size and cell density could be controlled within 12–40 μm and 5.0 × 107–1.3 × 109 cells/cm3, respectively.
Highlights
Polymer foams are multiphase and porous materials, which provide specific properties such as low density, high porosity, excellent thermal insulation, good sound absorption and high specific strength
0.05 g thermoplastic polyurethane (TPU) was cut from the compounded sample and dried at 80 ◦ C for 16 h to remove moisture
TPU samples were placed inside the high-pressure vessels (V-1 to V-3), immersed into a thermostatic oil bath to maintain the saturation temperature
Summary
Polymer foams are multiphase and porous materials, which provide specific properties such as low density, high porosity, excellent thermal insulation, good sound absorption and high specific strength. They have been used in various applications as separation media, controlled drug release carriers, tissue engineering scaffolds and structural materials [1,2,3]. Microcellular TPU foams show many excellent performances such as high strength, high toughness, outstanding abrasion-resistance and well-defined elasticity They have been used in electronics, sporting goods, footwear, automobiles and medical devices. The effect of foaming parameters on the properties of TPU foam are investigated and discussed
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