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A model is presented for free expansion polymer foam processing that includes simultaneous nucleation and bubble growth. The nucleation model includes dissolved gas, small critical cluster size, elastic, and non‐ideal solution effects. An influence volume approach, which couples nucleation and bubble growth, is used to account for the limited supply of dissolved gas. The resulting set of equations are solved using a combination of numerical techniques. A parametric study is conducted to examine the effects of key process variables on bubble growth, nucleation, and final bubble size distribution.

The foaming process of poly(ϵ‐caprolactone) (PCL) with carbon dioxide and nitrogen has been investigated in this work from a theoretical and experimental point of view. CO2 and N2 showed very different behavior, as foaming agents for PCL. This was due to the different transport, chemical, and physical properties of the polymer/gas mixture that led to different foam morphology in terms of density, cell number density, and cell size. The lowest density (0.03 g/cm3) was obtained with CO2, but the highest number of cells with N2 (although with a higher density, (0.2 g/cm3). Foam with a low‐density microcellular structure, was obtained when a mixture of the two gases was employed. POLYM. ENG. SCI., 45:432–441, 2005. © 2005 Society of Plastics Engineers

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