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Siegel der Universität
Department für Chemie - Arbeitsgruppe Prof. Strey

Sugar and Glass Foams by Continuity Inversion of Dispersions

Sandra Teusch, 2013

 

An important goal in current material science research is the production of highly porous materials for a wide variety of applications, for example as acoustic or thermal insulation materials. However, the production of such foams is challenging and therefore a topic of ongoing research. A new and promising processing concept is the Nanofoams by Continuity Inversion of Dispersions (NF-CID) procedure proposed by Strey and Müller. For this procedure, solid nano- (or micro-) particles (polymers, sugars, or glasses) are closely packed in a super- or near critical fluid matrix such as CO2 or water into a compression-proof, locked container. A continuity inversion occurs upon heating and melting of the particles, which creates sc-fluid inclusions within the continuous sugar or glass matrix. A porous foam is obtained by expansion, whereby the foam solidifies due to expansion cooling. This approach suggests to allow the production of porous foams in an inexpensive and simple way. In addition, foams of high melting point materials such as polymers or glasses should be available by this method. In this work sugar foams with a bimodal size distribution of pores in the ranges from 0.5 - 5 µm and 10 - 50 µm were obtained using NF-CID and sc-CO2 as blowing agent. In an additional experiment, a similar approach was applied in a first attempt to produce a glass foam. Therefore, a special cell for high pressures and temperatures was constructed. By the use of water as blowing agent, a glass foam with a bimodal structure ranging from 1.5 - 60 µm and 100 - 400 µm was produced. The results suggest that the NF-CID process shows great potential for producing glass foams with high porosity.