Effects of dope sonication and hydrophilic polymer addition on the properties of low pressure PVDF mixed matrix membranes

Abstract

Mixed matrix membranes (MMM) made from hydrophilic fillers incorporated into poly (vinylidene fluoride) (PVDF) are well known to have improved membrane properties and durability. However, the contributions from two key steps in MMM fabrication: dope sonication and the addition of a hydrophilic polymer like poly (vinylpyrrolidone) (PVP), have not been sufficiently highlighted. In this work, a range of MMM were made by extended dope sonication and stepwise PVP addition. The results showed that PVP, popularly referred to as a 'pore former', was surprisingly not responsible for pore formation but functioned rather as a 'pore connector' and as an aid to particle dispersion. While dope sonication resulted in efficient particle dispersion as may be expected, it did not improve membrane surface wettability as the hydrophilic nanoparticles were completely locked within the hydrophobic PVDF matrix. Sonication resulted in significant reduction in membrane porosity but did not change the membrane thermal stability. The addition of PVP, however, significantly reduced thermal stability as well as the PVDF β-phase mass fraction. The results of this study provide valuable insights to the effects of dope sonication and PVP addition for manufacturers and researchers developing low pressure membranes for water treatment applications.

PVDF Membrane Morphology—Influence of Polymer Molecular Weight and Preparation Temperature

“…These additives often show specific interactions with one of the other three components. Indeed, a number of publications focused on composite PVDF membranes have been published during the last decade [ 4 , 13 , 14 , 15 , 16 ]. However, different methods and strategies have been applied for the PVDF polymers production, which could impact their polymorphs [ 17 , 18 , 19 ].…”

Improvement in the blood compatibility of polyvinylidene fluoride membranes via in situ cross‐linking polymerization

“…[24][25][26][27] As the molecular chains of the polymeric matrix and polymeric additive are entangled, the hydrophilic additive can be "locked" into the polymeric matrix, thus effectively preventing hydrophilic additive washout. 28 In summary, according to our previous study, 14 respectively. All other reagents (AR) were obtained from Kelong Inc (Chengdu, China) and were used without further purification.…”

“…In an in situ cross‐linking polymerization process, polymerization and cross‐linking occur simultaneously; thus, in situ cross‐linking polymerization is a convenient and simple way for large‐scale fabrication in industry and has been widely used to design functional materials in the fields of fuel cells, water treatment, stimuli‐responsive materials, ion‐exchange membranes, and toxins removal . As the molecular chains of the polymeric matrix and polymeric additive are entangled, the hydrophilic additive can be “locked” into the polymeric matrix, thus effectively preventing hydrophilic additive washout …”

Preparation of Nano-SiO2/Al2O3/ZnO-Blended PVDF Cation-Exchange Membranes with Improved Membrane Permselectivity and Oxidation Stability

“…There are many methods that can be used for the modification of PVDF membranes, such as irradiation [18]. Currently, there are numerous reports on PVDF membrane modification by mixing the polymer with inorganic materials [7,19,20]. Organic nanoparticles are widely used because of their excellent properties, including good mechanical properties and stable chemical properties [21].…”