Hollow-fiber membranes of block copolymers by melt spinning and selective swelling

Selective Swelling of Stretched Block Copolymer Hollow Fibers for Upgraded Membrane Performance

“…Thus, after multiple attempts and systematical investigation, 200/210 °C with nitrogen as the protective atmosphere was selected as the processing temperature. In this case, the initial spinning speed reached a high value at 75 mm·min –1 , which is 5 times that reported in our previous work, significantly enhancing the production efficiency of the melt spinning process . In addition, as shown in Figure S2, all the spun PSF- b -PEG hollow fibers showed a light brownish color similar to that of the BCP granules, implying that the blanket of 2 L·min –1 nitrogen effectively avoids the oxidation of the copolymer even when spinning at such a high temperature.…”

“…All the detailed data on the dimensions of the hollow fibers subjected to stretching with different ratios are listed in Table . The results indicated that stretching effectively reduced the wall thickness of the hollow fibers, which is highly desired for the sake of improving the water permeance of HFMs . Meanwhile, an integral hollow structure and dense cross section were observed for all hollow fibers stretched at various stretching percentages.…”

“…PSF- b -PEG, composed of the high-strength PSF block and the flexible PEG block, is suitable for melt spun and stretching and can be cavitated by selective swelling . The hollow-fiber membranes prepared by melt spinning and selective swelling exhibited excellent tensile strengths . Besides, this block copolymer (BCP) is also available at large scale; therefore, PSF- b -PEG was chosen as a promising material and studied in this work.…”

“…For selective swelling, the PSF- b -PEG hollow fibers with different stretching percentages were immersed in the mixture of 80% Pa + 20% Ac (w/w) at 65 °C for 1 h and were then subjected to post-treatment and dried at 40 °C for 1 h until reaching a constant weight. , The thus-obtained HFMs were denoted as HFM- X , where X was the corresponding stretching percentage. The membranes after selective swelling were accordingly named HFM-0%, -13%, -100%, -247%, -380%, -527%, and -633%.…”

“…In this situation, melt spinning without solvents is undoubtedly emphasized. More recently, we reported a facile, efficient, and environmental-friendly strategy for the fabrication of ultrafiltration HFMs with well-defined porosities by selective swelling of melt-spun block copolymer hollow fibers . Hollow fibers of polysulfone- block -poly­(ethylene glycol) (PSF- b -PEG) with dense fiber walls were prepared via a continuous melt spinning process in which no organic solvent was required.…”