Preparation of flat sheet recycled PET membranes from high temperature solutions via a NIPS-TIPS hybrid separation process

Polyethylene terephthalate (PET) has very interesting properties for use as a membrane material and is available in large quantities as it is a recycling polymer. It has high mechanical and thermal stability, and its solvent resistance allows the use of organic solvents even at high temperature. However, this resistance to solvents makes it almost impossible to prepare porous membranes from PET via non-solvent induced phase separation (NIPS) under ambient conditions. So far, commercial PET membranes are prepared by track-etching of dense PET films. However, this type of membrane has insufficient porosity and permeability. In this study, a new, easy-to-implement approach to prepare PET membranes via NIPS-TIPS hybrid separation process using solutions of PET in N -methyl-2-pyrrolidone at elevated temperature (180 °C) is presented. By using heat, PET could be dissolved in sufficient concentrations for the preparation of membranes. By quickly applying these solutions to a substrate or glass plate and subsequent immersion in the coagulation bath, stable membranes were prepared. The various preparation parameters were investigated, and further focus was put onto investigating membrane preparation from different recycling sources. • rPET flat sheet membranes were prepared using hot NMP solutions. • Membrane properties were investigated in relation to casting conditions. • Different sources of rPET were successfully employed to prepare membranes. • Impurities can be removed by reprecipitation to enable membrane casting from highly impure rPET. • From waste to membranes.