Supercritical CO2 foaming of open-cell polypropylene/ethylene propylene diene monomer composite foams with oriented cellular structures for water treatment

摘要

Efficient treatment of tiny media in wastewater is a global challenge. Herein, an ingenious design to fabricate the highly open-cell polypropylene (PP)/ethylene propylene diene monomer (EPDM) composite foams for water treatment by using supercritical CO2 (scCO(2)) extrusion foaming coupling with post-stretching is presented. The tensile strain of high melt strength PP is fully utilized in an extensional flow field during foaming. Meanwhile, EPDM is added into PP matrix for obtaining the highly open-cell and oriented porous structures. Interestingly, a variety of structural transformations (like uniform, hollow and oriented cellular structures) can be achieved during extrusion foaming. Furthermore, the effects of different cellular structures on their selective filtration properties are studied. More interestingly, the as-prepared composite foam strips, with the highly open-cell content (similar to 94.4%) and orientation degree (similar to 89.6%), exhibit excellent selective filtration performance, which can successfully remove waste with particle size larger than 1 mu m (its filtration efficiency:similar to 99.52%). Water droplets can easily pass through the lengthy foam strips in seconds, but tiny particles (like oil droplets or glass microbeads) will be blocked. This work provides a new pathway to prepare highly open-cell composite foams with anisotropic porous structures for water treatment.