Two‐Stage Depressurization in Gas Dissolution Foaming: The Production of Nanocellular Materials Free of Defects

Nanocellular polymethylmethacrylate (PMMA) is produced through a newly proposed method, a two‐stage depressurization in the gas dissolution foaming process. This method modifies the depressurization step and allows controlling the pressure during cell growth, avoiding this way, the appearance of micrometric defects in the produced cellular materials. Three grades of PMMA, as well as different production parameters, are tested in order to study their influence on the final materials. Moreover, cellular structures are compared with those obtained with a one‐stage depressurization process. Additionally, this work analyzes the foaming mechanisms taking place during the production of nanocellular materials.