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Polymer film capacitors with high stability and reliability at elevated temperatures are promising for next‐generation power electronic systems and hybrid electric vehicles. In this work, sandwich‐structured composite films with good dielectric thermal stability were fabricated based on hybrid membranes of poly(vinylidene fluoride)/polyacrylonitrile blend nanofibrous skeleton highly filled with BaTiO3 nanoparticles. Composite films with 64.7 vol% BaTiO3 nanoparticles in the core layer exhibited high permittivity (38.1) and low loss (0.046) at 1 kHz and room temperature, and the dielectric permittivity and loss were only slightly increased to 41.5 and 0.08, respectively, at 120°C. Good dispersion and high loading of BaTiO3 nanoparticles in the composites films contributed to enhanced dielectric thermal stability and permittivity. Moreover, the composite films showed good flexibility, which could be ascribed to its sandwich‐structure. Our work paves a generic way to fabricate flexible composite films with excellent dielectric thermal stability via high loadings of ceramic nanoparticles. POLYM. COMPOS., 39:E1841–E1848, 2018. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT Ideal membranes toward separation of stable oil/water emulsions should have surface hydrophilicity and submicron pores in the separating layer. However, electrospun membranes made from poly(vinylidene fluoride) (PVDF) cannot meet these requirements, failing to remove oil droplets from a stable oil/water emulsion. By doping with a certain polyamide 6 solution, surface hydrophilicity, and interconnected pores with submicron size are successfully achieved. As a result, separation of a stable emulsion with an efficiency above 99% is exhibited by the modified PVDF membranes. Moreover, underwater oleophobicity of the modified PVDF membranes imparts them with good antifouling performance. The modified PVDF membranes could have great potentials in practical stable oil/water emulsion separation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44980. [ABSTRACT FROM AUTHOR]

ABSTRACT Effect of immiscible polyamide 6 (PA6) on the melt rheology and stretch-induced crystal transformation of poly (vinylidene fluoride) (PVDF) matrix is reported. PA6 is dispersed as submicron droplets in the PVDF matrix, responsible for significant enhancement in the melt elasticity. Nevertheless, crystallization habits of PVDF matrix from melt are little affected by submicron PA6 droplets, and the α-form of PVDF prevails in the blends. Upon mechanical stretching, the α-form is converted to the β-form, which is remarkably reduced with the increasing of PA6 content in the blends. It could be correlated with the decreased tensile stress in the presence of submicron PA6 droplets that act as stress concentrators. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43499. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(vinylidene fluoride) (PVDF) membranes with exclusive β-form have been directly obtained by immersion precipitation from the mixed solvents containing an ionic liquid (IL). In contrast, without the IL only the α-form is generated. The ion-dipole interactions between the IL and PVDF chains should account for the formation of the β-form with TTTT conformation. In addition, the presence of the IL accelerates the crystallization and gelation of PVDF, responsible for the particulate morphology and high water flux in the membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40505. [ABSTRACT FROM AUTHOR]

It is still a challenge to obtain polar phase of poly(vinylidene fluoride) from melt crystallization at normal conditions. This study demonstrates that polar β- and γ phases can be produced through melting re-crystallization of α phase, provided that moderate memory effects in the melt is achieved by annealing. Otherwise, it is inevitable to re-crystallize into α phase without any trace of polar phase. Small fragments, generated from the disintegration of long TGTG′ sequences, most likely adopt trans conformation in the melt before approaching random coils, thus responsible for the formation of polar phase upon cooling. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]

Abstract: The formation of γ phase in poly (vinylidene fluoride) is not rare from solution casting and high temperature melt crystallization. However, it is still a challenge to obtain γ phase with high melting point in a facile route. This study demonstrates that it can be readily realized via melt annealing of solution-cast films at 180°C, followed by subsequent re-crystallization upon rapid cooling in air. The re-crystallization into ordered γ phase arises from the formation of long TTTGTTTG'' sequences in the melt due to transformation of TTTT conformation of initial β phase, rather than from the melt memory effects of original γ phase. [Copyright &y& Elsevier]

Abstract: Melt crystallization of poly (vinylidene fluoride) (PVDF) usually produces nonpolar α-form, and the generation of polar β- and γ-forms is very rare. This study demonstrates that the presence of an ionic liquid in the PVDF significantly suppresses the α-form but promotes the β- and/or γ-form upon melt crystallization. Moreover, there exists a competition between the β- and γ-form, depending on the ionic liquid loading and cooling rate (crystallization temperature). Increasing the ionic liquid loading or cooling rate benefits the β-form with TTTT conformation but reduces the γ-form with TTTGTTTG′ conformation, and vice versa. It is highly expected that trans sequences induced by the ionic liquid as well as conformational rearrangements in the melt should be responsible for it. In addition, conformational ordering in the melt should account for rapid and direct formation of the γ-form at relatively low crystallization temperatures. [Copyright &y& Elsevier]

Electrospun polymer membranes have great potentials as separators for lithium-ion batteries due to their high porosity. However, electrospun membranes usually suffer from low mechanical strength because of weak bonding at inter-fiber junctions. In this study, high mechanical strength over 20 MPa is achieved for poly (vinylidene fluoride) (PVDF)/poly (acrylonitrile) (PAN) blend membranes at a ratio of 5/5 after modification by a PVDF dilute solution. Moreover, good dimensional stability at 200 °C is exhibited the modified blend membranes due to the presence of continuous PAN nanofibrils. Separators based on the modified blend membranes impart lithium-ion batteries with superior discharge capacity and cyclic performance. [ABSTRACT FROM AUTHOR]