Fabrication of poly (ECTFE) membranes via thermally induced phase separation

Poly (ethylene chlorotrifluoroethylene) (ECTFE) is a 1:1 alternating copolymer of ethylene and chlorotrifluoroethylene with an excellent combination of chemical, thermal and mechanical properties. Although the lack of a suitable solvent for ECTFE precludes membrane casting by conventional room-temperature processes of immersion precipitation or evaporative casting, thermally induced phase separation provides an attractive pathway for membrane fabrication. We have successfully identified three possible latent solvents for ECTFE and have studied the ECTFE-dibutyl phthalate (DBP) polymer-diluent system. ECTFE membranes were fabricated using a TIPS-casting apparatus that allowed control of several important process parameters. ECTFE membranes were characterized via scanning electron microscopy (SEM), porometry and permeation techniques. Results indicated that membranes with continuous pores having diameters in the microfiltration range (0.1–0.5 μm) could be reliably fabricated.