The hydrophilic polypropylene/poly(ethylene-co-vinyl alcohol) hollow fiber membrane with bimodal microporous structure prepared by melt-spinning and stretching

Luo, Dajun; Xie, Gaoyi; Qin, Shuhao

doi:10.1016/j.seppur.2021.118890

Cited by 11 publications

(12 citation statements)

References 32 publications

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“…The inner microstructure of the precursor films is critical to the microporous formation of stretched PP membranes [ 32 ]. Therefore, the crystal morphology of β-PP and the PA6 phase structure was examined by SEM first, as shown in Figure 1 a–c.…”

Section: Resultsmentioning

confidence: 99%

“…The compositions of three samples are displayed in Table 1 , where S and F represent the spherical and fibrillar PA6 phase morphologies, respectively. The compatibilizer, PPgMA, can react with PA6 to form the graft copolymer PP-g-PA6 [ 12 , 32 ]. It reduced the PA6 phase domain size and provided adequate adhesion between PP and PA6 to prevent film breakage during stretching.…”

Section: Methodsmentioning

confidence: 99%

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Microporous Formation Mechanism of Biaxial Stretching PA6/PP Membranes with High Porosity and Uniform Pore Size Distribution

Fang

Liang

et al. 2022

Polymers

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The low porosity and wide pore size distribution of biaxial stretching PP microporous membranes continue to be the primary impediments to their industrial application. To solve this problem, there is a critical and urgent need to study the micropore-forming mechanism of PP membranes. In this research, the interfacial micropore formation mechanism of PA6/PP membranes during biaxial stretching was investigated. PA6/PP membranes containing spherical PA6 and fibrillar PA6 were found to exhibit different interfacial micropore formation mechanisms. Numerous micropores were generated in the PA6/PP membranes, containing PA6 spherical particles via the interface separation between the PP matrix and PA6 spherical particles during longitudinal stretching. Subsequent transverse stretching further expanded the two-phase interface, promoting the breakdown and fibrosis of the PP matrix and forming a spider-web-like microporous structure centered on spherical PA6 particles. In PA6/PP membranes with PA6 fibers, fewer micropores were generated during longitudinal stretching, but the subsequent transverse stretching violently separated the PA6 fibers, resulting in a dense fiber network composed of PA6 fibers interwoven with PP fibers. Crucially, the PA6/PP biaxial stretching of microporous membranes presented an optimized pore structure, higher porosity, narrower pore size distribution, and better permeability than β-PP membranes. Furthermore, this study explored a new approach to the fabrication of high-performance PA6/PP microporous membranes, with good prospects for potential industrial application.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Microporous Formation Mechanism of Biaxial Stretching PA6/PP Membranes with High Porosity and Uniform Pore Size Distribution

Fang

Liang

et al. 2022

Polymers

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“…However, the above discussion is directed to the PPHFM with uniform pore structure which is formed by lamellae separation. Directed against the hydrophilic PP/EVOH-HFM reported in a previous study, , in the high-speed spinning process of PP/EVOH hollow fibers, theoretically the two-phase interface area and the EVOH phase would be deformed under the squeezing of the PP phase and interface action. The different magnitudes of stress imparted by different melt-draw ratios will inevitably affect the two-phase interface area and EVOH phase structure, which are crucial to the regulation of bimodal microporous structure.…”

Section: Introductionmentioning

confidence: 92%

“…In previous work, the bimodal microporous structure was designed and constructed in hydrophilic polypropylene (PP)/poly(ethylene- co -vinyl alcohol) (EVOH) hollow fiber membranes (PP/EVOH-HFMs) based on lamellae separation and phase separation to enhance pure water flux and maintain good rejection property . The models of PP/EVOH-HFMs with bimodal microporous structure and PP hollow fiber membranes (PPHFMs) with uniform pore are exhibited in Figure . It can be speculated that the formation of a bimodal microporous structure is based on the oriented lamellae and phase interfaces.…”

Section: Introductionmentioning

confidence: 99%

“…It can be speculated that the formation of a bimodal microporous structure is based on the oriented lamellae and phase interfaces. Although the raw material composition of PP/EVOH-HFMs played a significant role in the optimization of bimodal microporous structure, the lamellar structure of precursor hollow fibers that determined the membrane structure was mainly controlled by the adopted spinning conditions, such as the melt-draw ratio, temperature, and cooling condition. ,− The melt-draw ratio is positively correlated with the crystallinity and orientation of lamellae, which plays the most important role in the regulation of microporous structure of the membrane. , The conclusion that the stress applied to the fibers could increase the crystallinity of precursor hollow fibers was also reached by Rovère . There is an extreme value in the melt-draw ratios; therefore, the lamellae in precursor hollow fibers begin to be destroyed as the stress applied to the fibers further increases.…”

Section: Introductionmentioning

confidence: 99%

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Structure Regulation of Polypropylene/Poly(ethylene-co-vinyl alcohol) Hollow Fiber Membranes with a Bimodal Microporous Structure Prepared by Melt-Spinning and Stretching: The Role of Melt-Draw Ratio

Luo

Sun

Gao

et al. 2021

Ind. Eng. Chem. Res.

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High-performance polymeric hollow fiber membranes fabricated by a green and sustainable route have become the direction of the future. The bimodal microporous structure was green formed via melt spinning−stretching in the polypropylene (PP)/poly(ethylene-co-vinyl alcohol) (EVOH) hollow fiber membranes (PP/EVOH-HFMs) for improving the porosity and retaining the rejection performance. The relationship between the PP lamellar microstructure, the two-phase interface area, and the EVOH island morphology in PP/EVOH hollow fibers and the bimodal microporous structure in PP/EVOH-HFMs under different melt-draw ratios was established. The pore size of the bimodal microporous structure was controlled by regulating the melt-draw ratio. Small micropore sizes increased from 95 to 183 nm, and large micropore sizes decreased gradually from 3916 to 1054 nm with the melt-draw ratios increased. The porosity and pure water flux of PP/EVOH-HFM reached the maximum when the melt-draw ratio was 6000%. Moreover, the models of phase morphology and microstructure of PP/EVOH blends, PP/EVOH hollow fibers, and PP/EVOH-HFMs were built to explain the regulation mechanism of melt-draw ratio on the bimodal microporous structure of membranes.

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Tuning the microstructure of SMA/CPVC membrane for enhanced separation performance by adjusting the coagulation bath temperature

Chen

Luo

et al. 2022

J of Applied Polymer Sci

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In this study, styrene‐maleic anhydride copolymer/chlorinated polyvinyl chloride composite membranes were prepared via a non‐solvent induced phase separation technique. Different porous morphologies of the composite membranes were obtained by controlling the temperature of coagulation bath water. With the coagulation bath temperature increasing, the porous morphology of membrane surface changed from co‐continuous pores to isolated‐round‐pores, and its evolution mechanism was elaborated. The average pore size of membranes surface increased from 17.27 to 48.72 nm, the pure water flux increased from 225.50 to 624.47 L m−2 h−1, and the rejection rate of Congo red and bovine serum albumin declined gradually with the increase of coagulation bath temperature, but the NaCl rejection was less than 1.0%. The surface segregation behavior of anhydride groups was affected by the phase separation process, which in turn affects the anti‐fouling performance of membranes. The composite membranes obtained at the coagulation bath temperature of 20 and 30°C had large surface segregation of anhydride groups and excellent anti‐fouling performance. The water flux recovery rate is higher than 90% and the irreversible pollution decline rate is about 5.0%. Meanwhile, the obtained membranes, especially the membrane fabricated at a coagulation bath temperature of 0°C, has good dye/NaCl salt separation performance and can be used for the pretreatment of textile wastewater.

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The hydrophilic polypropylene/poly(ethylene-co-vinyl alcohol) hollow fiber membrane with bimodal microporous structure prepared by melt-spinning and stretching

Cited by 11 publications

References 32 publications

Microporous Formation Mechanism of Biaxial Stretching PA6/PP Membranes with High Porosity and Uniform Pore Size Distribution

Microporous Formation Mechanism of Biaxial Stretching PA6/PP Membranes with High Porosity and Uniform Pore Size Distribution

Structure Regulation of Polypropylene/Poly(ethylene-co-vinyl alcohol) Hollow Fiber Membranes with a Bimodal Microporous Structure Prepared by Melt-Spinning and Stretching: The Role of Melt-Draw Ratio

Tuning the microstructure of SMA/CPVC membrane for enhanced separation performance by adjusting the coagulation bath temperature

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