Controlling arrangement of multi‐layer microcellular materials by using supercritical fluids

A series of semicrystalline microcellular materials were prepared by the foaming technology using supercritical fluids. The distribution of multi‐size microcellulars and multi‐layer arrangement was observed by scanning electronic microscopy. By controlling the foaming condition accurately, the alternated arrangement of variable in cellular size may be tuned. One key point was discussed here to understand the phenomenon: the prior sequencing of the crystal nucleation and cellular nucleation. As the supporting experiments, the gravimetric desorption data of CO₂ were kinetically and thermodynamically evaluated by three diffusion equations. The concepts of local crystal nucleation and local cellular nucleation were introduced first, and the mechanism of multi‐layer arrangement was proved. Copyright © 2012 John Wiley & Sons, Ltd.