Crystallization behavior of PVDF in PVDF‐DMP system via thermally induced phase separation

Abstract

The crystallization behavior of PVDF (poly (vinylidene) fluoride) in PVDF-dimethylphthalate(DMP) system was investigated in the liquid-liquid (L-L) phase separation region, solid-liquid (S-L) phase separation region and different quenching conditions via thermally induced phase separation (TIPS). Differential scanning calorimetry (DSC) indicated the crystallinity of PVDF in PVDF-DMP system increased in the early stage of phase separation and polymer-rich phase crystallized completely in the late stage of phase separation. The scanning electron microscopy (SEM) showed the different quenching temperatures had effects on the spherulite size of polymer rich phase and the ultimate membrane structure in the different phase separation regions. The wide angle Xray diffraction (WAXD) was used to quantify the crystal structure of PVDF in PVDF-DMP system. The a-phase PVDF was obtained when the system quenched to different temperatures above 408C, and the area of diffraction peaks changed when quenching temperatures changed. While the b-phase PVDF was formed when PVDF-DMP system was quenched form liquid nitrogen and crystallized for 24 h in 258C water bath.

Effects of mixed diluent compositions on poly(vinylidene fluoride) membrane morphology in a thermally induced phase‐separation process

“…Both DBP (density 5 1.046 g/cm 3 ; boiling point 5 3408C) and DOP (density 5 0.985 g/cm 3 ; boiling point 5 3708C) were analytical reagents bought from Tianjin Yongda Chemical Reagent Co. (Tianjin Chemical Solvent Factory, Tianjin, China). The ethanol was an industrial product.…”

Effect of solution-blended poly(styrene-co-acrylonitrile) copolymer on crystallization of poly(vinylidene fluoride)

“…The sample (10 mg) was first heated from room-temperature to 200°C at a rate of 10°C/min and kept at this temperature for 3 min to eliminate thermal history, followed by the scan to 0°C at a cooling rate of 5°C/min, finally a heating rate of 10°C/min to 200°C. The degree of crystallinity X c was evaluated according to Equation (2) [17]: (2) where ΔH f was the endothermic heat during the melting process and ΔH * f was the heat fusion of a perfect crystal, taken as 104.5 J/g [18] for PVDF. φ was the weight fraction of PVDF in the blend.…”

Surface characteristics and blood compatibility of PVDF/PMMA membranes

“…Increasing PMMA content improves the hydrophilicity and processability of PVDF [13][14][15][16]. Particularly, PVDF is a semi-crystalline polymer having at least three regular conformations, namely, a, b, and c phases [17]. Among these polymorphs, b phase has the largest polarization per unit cell and exhibits the highest electroactive properties, whereas a phase has zero spontaneous polarization per unit cell and is non-piezoelectric [18].…”