Solid-state foaming is a relatively new process for producing closed-cell thermoset foams starting from powders. In this study, the possibility of introducing nanoclay into epoxy foams by solid-state foaming was investigated. The nanoclay was found to affect the foaming efficiency and the foam density; even if large nanoclay aggregates are present in the foams, for a small range of filler content (2.5-3 wt%), the mechanical properties are positively influenced, as shown by specific compressive toughness which attains a maximum value. Electron microscope observations provided important information on the dependence of the cell size on the filler percentage, and the presence of a critical size (about 5 mu m) of nanoclay aggregates, below which they are coherent with the matrix.
Mazzola, L., Bemporad, E., Squeo, E.a., Trovalusci, F., Tagliaferri, V. (2011). Filler-matrix interaction in solid-state foaming of composite foams. JOURNAL OF CELLULAR PLASTICS, 47(1), 31-43 [10.1177/0021955X10382955].