scholarly journals Effect of Polymer Dissolution Temperature and Conditioning Time on the Morphological and Physicochemical Characteristics of Poly(Vinylidene Fluoride) Membranes Prepared by Non-Solvent Induced Phase Separation

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4062
Author(s):  
João Teixeira ◽  
Vanessa Fernandes Cardoso ◽  
Gabriela Botelho ◽  
António Miguel Morão ◽  
João Nunes-Pereira ◽  
...  
Keyword(s):  
Phase Separation ◽  
Vinylidene Fluoride ◽  
Average Pore Size ◽  
Membrane Properties ◽  
Degree Of Crystallinity ◽  
Average Pore ◽  
Water Contact ◽  
Dissolution Temperature ◽  
Poly Vinylidene Fluoride ◽  
Polymer Dissolution

This work reports on the production of poly(vinylidene fluoride) (PVDF) membranes by non-solvent induced phase separation (NIPS) using N,N-dimethylformamide (DMF) as solvent and water as non-solvent. The influence of the processing conditions in the morphology, surface characteristics, structure, thermal and mechanical properties were evaluated for polymer dissolution temperatures between 25 and 150 °C and conditioning time between 0 and 10 min. Finger-like pore morphology was obtained for all membranes and increasing the polymer dissolution temperature led to an increase in the average pore size (≈0.9 and 2.1 µm), porosity (≈50 to 90%) and water contact angle (up to 80°), in turn decreasing the β PVDF content (≈67 to 20%) with the degree of crystallinity remaining approximately constant (≈56%). The conditioning time did not significantly affect the polymer properties studied. Thus, the control of NIPS parameters proved to be suitable for tailoring PVDF membrane properties.

Fast and simple fabrication of SiO2/poly(vinylidene fluoride) coated cotton fabrics with asymmetric wettability via a facile spray-coating route

2018 ◽  
Vol 89 (6) ◽  
pp. 1013-1026 ◽  
Author(s):  
Rongrong Yu ◽  
Mingwei Tian ◽  
Lijun Qu ◽  
Shifeng Zhu ◽  
Jianhua Ran ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Contact Angle ◽  
Water Contact Angle ◽  
Vinylidene Fluoride ◽  
Spray Coating ◽  
Cotton Fabrics ◽  
Water Repellent ◽  
Water Contact ◽  
Repellent Property ◽  
Poly Vinylidene Fluoride

Cotton fabrics with hydrophilic-to-hydrophobic asymmetric surfaces are attractive as potential utilizable structures for functional garments. The spray-coating route could be deemed as a fast and simple way to achieve asymmetric surfaces. In this paper, SiO2 nanoparticles with size ∼ 205 nm were synthesized via the modified sol-gel method, and then modified with poly(vinylidene fluoride) (PVDF) to form a hydrophobic surface. The SiO2 nanoparticles modified with PVDF were uniformly deposited on the outer surface of cotton fabric aided with the robust air flow force from the sprayer. The morphology and chemical structures were characterized by scanning electron microscopy, mapping, atomic force microscopy, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The results indicated that SiO2 nanoparticles were evenly deposited on the surface of cotton fibers and stable interfacial interaction occurred between SiO2 and PVDF molecular chains. The existence of SiO2 could increase the roughness of the fabric surface, which could enhance the water-repellent property of the coated fabrics. Furthermore, the water-repellent property and thermal insulation properties were evaluated via the water contact angle and thermal conductivity tests, respectively, and the results showed that 20 wt.% SiO2/PVDF fabric achieved a desirable level of contact angle, 136.6°, which was the largest water contact angle among all the samples, and the lowest thermal conductivity of 0.033 W/mK, resulting from the existence of SiO2 nanoparticles. Such a fast and simple spray-coating strategy could be widely introduced into asymmetric fabric modification, and such asymmetric fabrics with reasonable water-repellent and thermal insulating outer surfaces could act as candidates in the field of functional garments.

scholarly journals Reduction of Biofouling of a Microfiltration Membrane Using Amide Functionalities—Hydrophilization without Changes in Morphology

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1379
Author(s):  
Daniel Breite ◽  
Marco Went ◽  
Andrea Prager ◽  
Mathias Kühnert ◽  
Agnes Schulze
Keyword(s):  
Membrane Fouling ◽  
Average Pore Size ◽  
Membrane Surface ◽  
Aqueous Media ◽  
Soxhlet Extraction ◽  
Hydrophobic Membrane ◽  
Average Pore ◽  
Water Contact ◽  
Microfiltration Membrane ◽  
Membrane Performance

A major goal of membrane science is the improvement of the membrane performance and the reduction of fouling effects, which occur during most aqueous filtration applications. Increasing the surface hydrophilicity can improve the membrane performance (in case of aqueous media) and decelerates membrane fouling. In this study, a PES microfiltration membrane (14,600 L m−2 h−1 bar−1) was hydrophilized using a hydrophilic surface coating based on amide functionalities, converting the hydrophobic membrane surface (water contact angle, WCA: ~90°) into an extremely hydrophilic one (WCA: ~30°). The amide layer was created by first immobilizing piperazine to the membrane surface via electron beam irradiation. Subsequently, a reaction with 1,3,5-benzenetricarbonyl trichloride (TMC) was applied to generate an amide structure. The presented approach resulted in a hydrophilic membrane surface, while maintaining permeance of the membrane without pore blocking. All membranes were investigated regarding their permeance, porosity, average pore size, morphology (SEM), chemical composition (XPS), and wettability. Soxhlet extraction was carried out to demonstrate the stability of the applied coating. The improvement of the modified membranes was demonstrated using dead-end filtration of algae solutions. After three fouling cycles, about 60% of the initial permeance remain for the modified membranes, while only ~25% remain for the reference.

Does dynamic vulcanization induce phase separation?

Soft Matter ◽  
2014 ◽  
Vol 10 (30) ◽  
pp. 5550-5558 ◽  
Author(s):  
Mohammad Mahdi Abolhasani ◽  
Fatemeh Zarejousheghani ◽  
Minoo Naebe ◽  
Qipeng Guo
Keyword(s):  
Phase Separation ◽  
Crosslink Density ◽  
Vinylidene Fluoride ◽  
Dynamic Vulcanization ◽  
Miscible Blends ◽  
Poly Vinylidene Fluoride ◽  
Induce Phase Separation ◽  
Induce Phase

Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslink density on phase separation.

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