Microchannel‐Assisted Supercritical <scp>CO₂</scp> Rapid Diffusion Strategy for Efficient Polymethyl Methacrylate (<scp>PMMA</scp>) Foaming

ABSTRACT The slow diffusion rate of supercritical CO 2 in polymer matrices leads to long saturation times, significantly limiting the production efficiency of intermittent supercritical fluid foaming. In this study, a novel approach is proposed to shorten the saturation time by designing and constructing micron‐scale interconnected channels within PMMA sheets. PMMA sheets (2.4 mm thick) with microchannel structures can achieve supercritical foaming in approximately 20 min, with the saturation time reduced by over 90% compared to PMMA sheets with dense structures. Through experimental and simulation analyses, the diffusion rates of PMMA sheets with different microchannel structures and their effects on foaming performance were investigated. The microchannel‐assisted strategy not only reduces CO 2 diffusion depth to the micron scale, shortening saturation time, but also forms supercritical CO 2 aggregation zones within the PMMA sheets, forming a bimodal cell structure. The optimized PMMA foam exhibits low density (0.11–0.15 g cm −3 ), excellent thermal insulation (thermal conductivity 0.0461 W m −1 K −1 ), and unique two‐stage compression stress plateau characteristics. This method provides new insights into improving supercritical fluid foaming efficiency for industrial applications.