Porous membranes of thermosetting polybenzoxazine resins with interconnected-pores for organic solvent microfiltration

Employing crosslinkable polybenzoxazine (PBz) as the precursor, thermosetting resin based porous membranes possessing interconnected pores are prepared and applied for organic solvent phase microfiltration. The effects of the used solvents and additives on formation of interconnected pores in the obtained membranes are studied. Employing a solvent or an additive, which could build up hydrogen bonding based networks in the PBz solution, favors the formation of interconnected pores in the resulting membranes, as the polymer-solvent and polymer-additive networks could retard the mass transfers to result in a delayed demixing mechanism in the phase separation processes. 2-Pyrrolidone and lignin is an effective solvent and additive for formation of crosslinked PBz with interconnected pores. The crosslinked PBz/lignin membrane shows a high resistance to solvents, a high surface hydrophobicity with a water contact angle of about 141°, a high porosity of 70%, and a small pore size of 0.55 ± 0.05 μm. While being applied to a gravity-driven separation on a surfactant-stabilized water-in-toluene emulsion, the membrane demonstrates a flux of 278 ± 21 Lm−2h−1 and a water content of 474 ± 3 ppm of the permeated toluene, which is close to the natural solubility of water in toluene (411 ppm). This work has explored a new class of thermosetting resin based membrane with interconnected pores suitable for organic solvent microfiltration.