Kinetics of Thermally Induced Phase Separation in the PVDF Blend/Methyl Salicylate System and Its Effect on Membrane Structures

Abstract

Microporous membranes were prepared via thermally induced phase separation of a poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend (with mass ratio = 70/30)/methyl salicylate system. The differential scanning calorimetry results revealed that the observation of double melting phenomenon in quenched samples was a result of a variation in the morphology (different crystal size or perfection of crystals), which formed during the sample preparation. When the samples were quenched at 118°C, 110°C, and 100°C, a spherulitic structure was present in the membranes due to the crystallization of PVDF. As the holding time period increased, the crystallization of PVDF was enhanced owing to the aggregation of a polymer-rich phase (PVDF/PMMA blend) during the phase separation. The structure of the resulting PVDF blend membranes, detected by scanning electron microscopy, was greatly affected by liquid–liquid phase separation and the crystallization of PVDF in the mixture.

Keywords:

• blend
• membrane preparation
• membrane structure
• poly(vinylidene fluoride) (PVDF)
• thermally induced phase separation (TIPS)

Acknowledgment

This work was supported by the National Basic Research Program of China under contract No. 2009CB623404.