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Synergy of supercritical CO2 and superheated H2O for enhanced processability of polyethersulfone towards open cell foams
Authors:Silas Owusu‐Nkwantabisah  Claudia Staudt  Alan J Lesser
Affiliation:1. Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts;2. Advance Materials and Systems Research, BASF SE, GMM/M ‐ B001, Ludwigshafen, Germany
Abstract:Processing of a high glass transition (Tg) polymer such as polyethersulfone (PES; Tg = 225°C) poses a challenge as it requires high processing temperatures or sometimes toxic solvents. In this work, we report of a facile process using superheated water (shH2O) and supercritical carbon dioxide (scCO2) co‐media. PES solids were foamed in the scCO2/shH2O co‐media or scCO2 alone in a batch process at different temperatures. The scCO2/shH2O produced a synergistic effect and achieved PES foams even at processing temperatures as low as 85°C below the nominal Tg; whereas, scCO2 alone required higher processing temperatures. Moreover, the scCO2/shH2O co‐media produced highly porous PES foams that were at least 23% higher in porosity than what was obtained using scCO2 alone. In addition, the scCO2/shH2O produced open cell foams at some processing conditions; whereas, scCO2 produced closed cell morphologies. Since both CO2 and H2O are innocuous, this approach has potential for use in the preparation of ultrafiltration membranes, which currently require the use of toxic solvents for their fabrication by way of the phase inversion process. Moreover, the use of scCO2/shH2O is a cost‐effective approach for the processing of high Tg polymers at significantly lower temperatures. POLYM. ENG. SCI., 58:1108–1114, 2018. © 2017 Society of Plastics Engineers
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