Open-Celled Foams of Polyethersulfone/Poly(N-vinylpyrrolidone) Blends for Ultrafiltration Applications

Abstract

Since membranes made of open porous polymer foams can eliminate the use of organic solvents during their manufacturing, a series of previous studies have explored the foaming process of various polymers including polyethersulfone (PESU) using physical blowing agents but failed to produce ultrafiltration membranes. In this study, blends containing different ratios of PESU and poly(N-vinylpyrrolidone) (PVP) were used for preparation of open-celled polymer foams. In batch foaming experiments involving a combination of supercritical CO2 and superheated water as blowing agents, blends with low concentration of PVP delivered uniform open-celled foams that consisted of cells with average cell size less than 20 µm and cell walls containing open pores with average pore size less than 100 nm. A novel sample preparation method was developed to eliminate the non-foamed skin layer and to achieve a high porosity. Flat sheet membranes with an average cell size of 50 nm in the selective layer and average internal pore size of 200 nm were manufactured by batch foaming a PESU blend with higher concentration of PVP and post-treatment with an aqueous solution of sodium hypochlorite. These foams are associated with a water-flux up to 45 L/(h m² bar). Retention tests confirmed their applicability as ultrafiltration membranes.

Open-Celled Foams from Polyethersulfone/Poly(Ethylene Glycol) Blends Using Foam Extrusion

“…Polyarylsulfone foams have been studied for the last couple of decades for use in various applications. Using the method of batch foaming, highly porous microcellular foams, as well as nanocellular foams, have been produced with PESU, PSU, PPSU and their blends [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ].…”

“…In previous studies, researchers used polymer blends that delivered higher porosity and smaller cell sizes than their respective homopolymers [ 14 , 18 , 19 , 20 , 21 ]. As the processing temperatures for PESU lie near or above the degradation temperatures of most polymers, it is essential to lower the processing temperature.…”

“…As the processing temperatures for PESU lie near or above the degradation temperatures of most polymers, it is essential to lower the processing temperature. Poly( N -vinylpyrrolidone) (PVP), a water-soluble polymer, results in improved porosity and pore size in foams of blends with PESU manufactured using batch foaming [ 14 , 22 ]. PVP, however, is susceptible to crosslinking at higher temperatures and is not directly processable in an extruder with PESU [ 23 ].…”

Large‐scalable polar bear hair‐like cellular hollow fibers with excellent thermal insulation and ductility

“…Rizvi et al 18 reported a hollow fibrillar foam via large‐scale melting extrusion. Gas bubbles nucleated and grew in fibrillar polymer melt that ultimately solidified to form a hollow cellular configuration 19 . Combining spinning and foaming may arouse an as‐expected strategy to synthesize hollow cellular fibers with biomimetic conformation.…”

“…Gas bubbles nucleated and grew in fibrillar polymer melt that ultimately solidified to form a hollow cellular configuration. 19 Combining spinning and foaming may arouse an as-expected strategy to synthesize hollow cellular fibers with biomimetic conformation. To the best of our knowledge, there is rare work in this field and corresponding warm-keeping textiles.…”