Effect of polyethylene glycol (PEG) as an additive on the fabrication of polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) asymmetric microporous hollow fiber membranes
Journal article
Authors/Editors
Strategic Research Themes
No matching items found.
Publication Details
Author list: Wongchitphimon S., Wang R., Jiraratananon R., Shi L., Loh C.H.
Publisher: Elsevier
Publication year: 2011
Journal: Journal of Membrane Science (0376-7388)
Volume number: 369
Issue number: #
Start page: 329
End page: 338
Number of pages: 10
ISSN: 0376-7388
eISSN: 1873-3123
Languages: English-Great Britain (EN-GB)
View in Web of Science | View on publisher site | View citing articles in Web of Science
Abstract
Polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) has received much attention recently as a promising membrane material for membrane contactor application. A systematic study has been carried out to investigate the effects of polyethylene glycol (PEG) with different molecular weights and different loadings as an additive on the fabrication of PVDF-HFP asymmetric microporous hollow fiber membranes. Moreover, the synergetic effects of coagulation temperature and the second additive (lithium chloride: LiCl) with PEG are also evaluated.Experiments revealed that the addition of PEG into the PVDF-HFP/NMP solution resulted in the system thermodynamically less stable in reaction with water, promoting rapid phase demixing in the phase inversion process. When the same 3. wt% PEG was added into the dope solution, the dimension of finger-like macrovoids of the resultant membrane increased in parallel with the increase of PEG molecular weight from 200 to 600 and 6000. kDa, and pure water permeability (PWP) also increased accordingly. An increase in PWP was also observed when PEG-200 loading in the dope solution was increased from 3 to 5 and 10. wt%, corresponding to the morphology change of resultant membranes.As a synergetic effect of coagulation temperature with PEG, the finger-like pores occurred in the membrane at room temperature expanded to much larger macrovoids using 10ฐC water as the coagulant, and the big finger-like pores almost disappeared when the coagulation bath temperature was increased to 40ฐC because of delayed phase demixing. The big macrovoid size can also be suppressed by adding the second small molecule additive, LiCl, due to its strong interactions with NMP and PVDF-HFP to delay the dope precipitation. The irregular inner contour of the membrane can be eliminated by the increase of coagulation bath temperature to 40ฐC. The hollow fiber membrane made by a dope of PVDF-HFP/PEG-6000/LiCl/NMP (15/3/3/79 in weight) using 40ฐC water as the coagulant exhibited a high PWP of 117L/m2hatm and reasonably good MWCO of 150kDa. An improvement has been made in the current work as compared to previous PVDF-HFP hollow fiber membranes reported in literatures. ฉ 2010 Elsevier B.V.
Keywords
Coagulation temperature, Hollow fiber membrane, PEG additive, PVDF-HFP
Contact Information