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Evaluation of Nanoparticle Effect on Bubble Nucleation in Polymer Foaming

Wang, Linyan, Zhou, Hongfu, Wang, Xiangdong, Mi, Jianguo
The Journal of Physical Chemistry C 2016 v.120 no.47 pp. 26841-26851
carbon dioxide, foaming, nanocomposites, nanoparticles, physical chemistry, polymethylmethacrylate, polystyrenes, silica
We present a density functional approach to calculate the free-energy barriers, critical radii, and nucleation rates of bubble nucleation in polystyrene and poly(methyl methacrylate) nanocomposites. In particular, the effects of surface geometry and chemistry of nanoparticles on bubble morphology and cell density have been evaluated with consideration of the local supersaturation of dissolved CO₂ molecules and the local subsaturation of polymer chains. It is shown that addition of SiO₂ or fluorinated SiO₂ particles can improve the nucleation rates up to 4 or 5 orders of magnitude, and the critical radii shrink down to approximately half of the homogeneous nuclei, which are very helpful to fabricate low density foaming materials. The theoretical approach has been tested by the available experimental data and is expected to provide a reasonable explanation for the mechanism of inhomogeneous polymer foaming at the molecular level.