Preparation and characterization of ECTFE solvent resistant membranes and their application in pervaporation of toluene/water mixtures

Abstract

In this work, polymeric membranes have been prepared by thermal induced phase inversion (TIPS) using Ethylene–Chlorotrifluoroethylene copolymer (ECTFE). N-methyl pyrrolidone (NMP) has been used as solvent. Moreover, four different additives, i.e. glycerol triacetate (GTA), triethyl citrate (CTF), dibutyl itaconate (DBI) and diethyl adipate (DEA), have been tested in order to improve polymer processability. The microstructure of the obtained membranes has been analyzed by scanning electron microscopy (SEM). In all cases, asymmetric membranes, made up of two layers have been observed: the bottom side consists of spherulitic structures, which develop as a consequence of polymer crystallization; at the top side, a fully dense skin, having variable thickness, can be observed. Membranes show excellent resistance to most aggressive organic solvents, such as: Dimethyl Formamide (DMF), Dimethyl Acetamide (DMA), N-methyl pyrrolidone (NMP), Tetrahydrofuran (THF), toluene, Chloroform and Acetone. For each solvent, solvent uptake tests of 72h have been performed. Besides, solvent uptake tests have been carried out using organic solvent/water and organic/organic mixtures. The obtained results suggest that the prepared ECTFE dense membranes are very promising candidates for organic solvents pervaporation but also for nanofiltration. Preliminary pervaporation (PV) tests on aqueous solutions of toluene (200–250ppm) have been also carried out.