Gas dissolution foaming is one of the most employed methods to fabricate micro and nanocellular polymers, which are materials composed of solid and gas phases. Despite all benefits (environmental respectfully process, controlled and tunned cellular structures…), polymer foams fabricated by gas dissolution foaming always show non-foamed solids skins covering the cellular core. That defect is related to the fast diffusion of the gas in the borders of the polymer during the foaming process, promoting the mentioned solid skins. This drawback avoids the exposure of the cellular structure to the external medium, limiting their physical properties, and their potential application of the cellular polymers in several fields, such as filtration, catalysis.

In this work, a novel approach was designed to improve the gas dissolution foaming process in order to avoid the appearance of the non-foamed solids skins in the cellular polymers. The idea is based on a gas diffusion barrier placed over the surfaces of the polymer, which delays the diffusion during the pressure drop stage, remaining an appropriate gas concentration in the edges to obtain completely foamed polymers. Besides, this technique has allowed foaming systems with the same magnitude of the solid skins formed, it means in the micrometric range, which previously could not be foamed using this foaming technique.