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Micro- and nanofoams

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The aim of this topic is to prepare micro- and nanofoams of various morphologies. Polymer foams are widely used for their heat and acoustic insulation properties. According to mathematical modeling, heat insulation properties can be improved by (i) ballistic (Knudsen) effect for the average cell size smaller than several microns and (ii) reduced heat radiation in foams with the cell sizes smaller than 100 µm. However, conventional polymer foams have the cell size larger than 100 µm (Figure 1a). Thus, the production of the so-called micro- or nano-cellular foams with the cell sizes smaller than 10 µm or 1 µm would improve the heat insulation properties.

Currently, we are being focused on the preparation of microcellular polymer foams via pressure and temperature induced foaming with CO2 as the blowing agent at high pressures (Figure 1b). We study the influence of the process conditions on the final polymer foam structure which is investigated by X-ray micro-CT, SEM and AFM. The cell size distribution, porosity and cell density is also evaluated to gain the quantitative description about foam morphology.

 

The other methods, we employed, is spinodal decomposition (SD) for preparation of open cell foams (Figure 2a) on the custom built apparatus. The SD foaming process involves several steps. The initial solution is prepared by the dissolving of the polymer in a suitable solvent above critical temperature of the solution. Then, a rapid temperature quench follows. As the temperature decreases, the system goes through the metastable region under the binodal to the unstable region (under the spinodal). In this part of the process, the phase separation takes place until the solution freezes. In the last step, the frozen solvent is removed by lyophilization. The whole foaming process is illustrated in Figure 2b.

 

Contact

Juraj Kosek
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+420 220 443 296

University of Chemistry and Technology Prague
Department of Chemical Engineering
Technicka 5
166 28 Prague 6
Czech Republic

University of West Bohemia
New Technologies Research Centre (NTC)
Univerzitní 8
306 14 Pilsen
Czech Republic