No abstract

Bu çalışmada, gözenek oluşturucu olarak polivinilpirrolidonun (PVP), polisülfon (PSF) membran performansı üzerindeki etkisi incelenmiştir. XRD spektrumları, artan PVP miktarı ile kristalin fazdan amorf faza geçişinin gerçekleştiğini ortaya koydu. SEM sonuçları, membranlardaki makro boşlukların şekli ve boyutunun, polimer çözeltisindeki artan PVP miktarı ile değiştiğini gösterdi. Saf PSF ve ağırlıkça % 5 PVP ilave edilmiş PSF membranı için Tg değerleri sırasıyla 189 °C ve 182 °C olarak ölçülmüştür. Membranların performansı, Saf Su Akışı (SSA) ölçümleri kullanılarak belirlendi. Membranların SSA'sı PSF polimer çözeltisinde PVP miktarının (ağırlıkça %0'dan %10'a) artmasıyla 36.76 L m -2 s -1 'dan 86.80 L m -2 s -1 'e yükselmiştir. SSA ve PVP içeriği arasındaki ilişki artan termodinamik kararsızlık ve kinetik engel ile açıklanmıştır.

Polyvinylidene fluoride (PVDF) membranes were prepared via the phase inversion method from casting solutions containing PVDF, dimethylformamide (DMF), and polyvinylpyrrolidone (PVP) as pore former. PVP was used in the casting solution in a range of 0–5 wt % and extracted. The effect on membranes of using PVP in the casting process was analyzed by X‐ray diffraction, differential scanning calorimetry, scanning electron microscopy, viscosity, and water permeability techniques. With an increase of PVP from 0 to 5 wt %, the PVDF casting solution viscosities increased from 858 to 1148 cP; the resulting PVDF membrane thickness increased; and the crystallinity of PVDF membranes decreased from 40.0 to 33.3%, which indicates that the addition of PVP inhibits the degree of crystallization in the PVDF membranes. SEM results revealed the shape and size of macropores in the membranes; these macropores changed after PVP addition to the casting solutions. The impact of structural changes on free‐volume properties was evaluated using positron annihilation lifetime spectroscopy (PALS) studies. PALS analysis indicated no effect on the average radius (~3.4 Å) of membrane free‐volume holes from the addition of PVP to the casting solution. However, the percentage of o‐Ps pick‐off annihilation intensity, I3, increased from 1.7 to 5.1% with increased PVP content. Further, increasing the PVP content from 0.5 to 5% resulted in an increased final pure water permeability flux. For instance, the 210 min flux for a 14% PVDF + 0.5% PVP membrane was found to be 3.3 times greater than a control membrane having the same PVDF concentration. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 589–598

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