US EPA

1600014 

Journal Article 

Morphologies and crystalline forms of polyvinylidene fluoride membranes prepared in different diluents by thermally induced phase separation 

Yang, J; Wang, XLin; Tian, Ye; Lin, Y; Tian, F 

2010 

Yes 

Journal of Polymer Science. Part B, Polymer Physics
ISSN: 0887-6266 

48 

23 

2468-2475 

English 

10.1002/polb.22145 

WOS:000284227500006 

https://search.proquest.com/docview/2000020736?accountid=171501
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We have studied the morphologies and crystalline forms of
polyvinylidene fluoride (PVDF) membranes separately prepared in four different diluents bearing
>C=O groups, namely 1,2-propylene glycol carbonate (PGC), dimethyl phthalate (DMP), diphenyl
ketone (DPK), and dibutyl phthalate (DBP), by the thermally induced phase separation (TIPS)
method. The permittivities of the diluents and PVDF were measured to compare the different PVDF-
diluent systems. The results showed the permittivity of PGC to be much greater than that of PVDF,
and those of DMP and DBP to be lower than that of PVDF. The permittivity difference between DPK
and PVDF was not apparent above 120 degrees C. On cooling mixtures with a PVDF concentration of
10 wt %, PVDF crystallization was observed in the PVDF-DMP, PVDF-DBP, and PVDF-PGC systems, while
liquid-liquid phase separation occurred in the PVDF-DPK system. A cross-section of the PVDF-PGC
membrane presented smooth PVDF particles in the beta-phase crystalline form. Those of the PVDF-
DMP and PVDF-DBP membranes presented PVDF particles consisting of a fibrillar network in the a-
phase. The PVDF-DPK membrane preferentially adopted an a-phase bicontinuous channel structure.
When the concentration of PVDF was 60 wt %, the cross-sections of the above four membranes
revealed PVDF polyhedra, among which the PVDF-DMP, PVDF-DBP, and PVDF-DPK membranes retained the
a-phase crystalline form, and the diffraction peak of the a-phase became visible in the X-ray
diffraction (XRD) spectrum of the PVDF-PGC membrane. (C) 2010 Wiley Periodicals, Inc. J Polym Sci
Part B: Polym Phys 48: 2468-2475, 2010 

crystallization; crystalline form; membranes; morphology; permittivity; phase separation; polyvinylidene fluoride membrane; thermally induced phase separation