Oleg Klems, September 2008
Melamine formaldehyde resin foams are a building material of great importance because of their flame-retarding, sound-absorbing characteristics. A refinement of their structure on nanoscale can represent the foam material of the future with clearly smaller thermal conductivity. An innovative way to produce nanofoams is the Principle of Supercritical Microemulsion Expansion (POSME). In order to fix the structure of nanofoams produced in this way, in this work melamine formaldehyde resin (MF) microemulsions were formulated using propane as propellant. The starting point of this study was the phase behavior of MF-microemulsions which was systematically examined at atmospheric pressure using n-octane as oil. The microstructure of these systems is characterized with the help of dynamic light scattering and scanning electron microscopy. For the polymerization reaction an optimal catalyst content of formic acid was determined. Using these optimal polymerization conditions, the bicontinuous and lamellar nanostructures could be fixed by cross-linking the resin without phase separation. Already following first preliminary experiments with propane, closed cellular foams with nanometer-thin windows could be produced.