PVDF Component Research Articles

A Fluorinated‐Polyimide‐Based Composite Nanofibrous Separator with Homogenized Pore Size for Wide‐Temperature Lithium Metal Batteries

Lithium (Li) is known for excellent theoretical specific capacity and most negative electrochemical potential, while still restricted by the irregular lithium dendrites and safety risks in practical applications of lithium metal batteries (LMBs) due to thermal runaway. Herein, a fluorinated‐polyimide (F‐PI)‐based composite nanofibrous separator containing poly(vinylidene fluoride) (PVDF) component, which is designed as PVDF/F‐PI, is developed via a facile electrospinning strategy for wide‐temperature LMBs. First, abundant polar trifluoromethyl (–CF3) groups in F‐PI create an electronegative environment to facilitate rapid Li‐ions (Li+) transport. Meanwhile, the PVDF component, acting as both the physical linker between F‐PI nanofibers and the regulator of homogenized pore size, simultaneously improves the mechanical properties and homogenizes the Li+ flux on the electrode surface. Therefore, a steady circulation of 2400 h is achieved for the symmetric cell using PVDF/F‐PI separator, which still displays a stable cycle life with a low voltage polarization of 15 mV in 1000 h even under 60 °C. Therefore, the fluorinated‐PI‐based composite nanofibrous separator with high ionic conductivity and uniform pore structure offers a practical method for design of functionalized separators in wide‐temperature LMB applications.

(PVDF)2(PEO)2 miktoarm star copolymers: Synthesis and isothermal crystallization leading to exclusive β-phase formation

In this work, we study how chain topology can induce different polymorphic behaviors in poly(vinylidene fluoride) (PVDF)-based materials. A linear PVDF precursor with two azido groups at the junction point, (PVDFx-N3)2 and three 4-miktoarm star copolymers (PVDFx)2-b-(PEOy)2 with two poly(ethylene oxide) (PEO) and two PVDF arms were synthesized and employed in this study. The amphiphilic miktoarm copolymers were prepared by a combination of anionic ring-opening polymerization, iodine transfer radical polymerization (ITP), and copper-catalyzed azide-alkyne cycloaddition (CuAAC). They have practically similar overall molar mass but different compositions, ideal for performing bulk morphology and crystallization investigations. The isothermal overall crystallization kinetics of the PVDF and PEO arms of the 4-miktoarm star copolymers and representative PEO and PVDF precursors was determined by Differential Scanning Calorimetry (DSC). The results indicate that the star arms crystallized faster than the equivalent precursors as the kinetics are dominated by nucleation effects. The phases formed by the PVDF components in the materials examined were analyzed by studying their melting behavior by DSC, their superstructural morphology by Polarized Light Optical Microscopy (PLOM), and the phase structure by Fourier Transform Infrared Spectroscopy (FTIR). The linear PVDF and (PVDF29-N3)2, exhibited α, β and γ-phases (with a majority of β-phase formation) during melting after isothermal crystallization. The ratio of the different phases depends on the crystallization temperature. An analysis of the multiple melting behavior indicated that the sample forms both α and β-phases initially, and the α-phase partially transforms into the γ-phase during isothermal crystallization when the temperature of crystallization increases. We found a remarkable behavior for the 4-miktoarm star copolymers, as the PVDF arms only form the ferroelectric β-phase when all three materials were isothermally crystallized regardless of the crystallization temperature employed. The presence of the polymorphism in the PVDF was detected by DSC, PLOM, and FTIR. Hence, we have shown that tailoring chain topology in PVDF copolymers can lead to exclusive β-phase formation, a path that can be exploited for future piezoelectric applications.

The Impact of Interfacial Interactions on Structural, Electronic, and Sensing Properties of Poly(3‐methylthiophene) in Core‐Shell Nanocomposites. Application for Chemical Warfare Agent Simulants Detection

AbstractIn this paper, structural, electronic, and sensing properties of the poly(3‐methylthiophene) (P3MT) in two types of its core–shell nanocomposites with multiwall carbon nanotubes (MWCNTs) and poly(vinylidene fluoride) with different contents of the P3MT component (shell) are explored and are compared. The results indicate specific changes in the P3MT properties appear due to its interfacial interactions with the MWCNTs and PVDF components. In the case of the doped P3MT, charge transfer from MWCNT to P3MT leads to partial dedoping of the latter. The evidence of intermolecular charge transfer complex formation between undoped P3MT (donor) and MWCNTs (acceptor) is obtained. Changes in the properties of P3MT in nanocomposites are used to detect and to reliably recognize some chemical warfare agent's simulants of nerve agents and mustard gas. The sensitivity dependences of the nanocomposites on their work functions, Hansen solubility parameters and analytes electronegativity are studied. It is shown that the sensor response is controlled by a partial charge transfer if the difference between the work function of the sensing material and the electronegativity of the analyte molecules does not exceed a certain value (in the case herein ≈0.3 eV).

Phase Transitions in Poly(vinylidene fluoride)/Polymethylene-Based Diblock Copolymers and Blends.

The crystallization and morphology of two linear diblock copolymers based on polymethylene (PM) and poly(vinylidene fluoride) (PVDF) with compositions PM23-b-PVDF77 and PM38-b-PVDF62 (where the subscripts indicate the relative compositions in wt%) were compared with blends of neat components with identical compositions. The samples were studied by SAXS (Small Angle X-ray Scattering), WAXS (Wide Angle X-ray Scattering), PLOM (Polarized Light Optical Microscopy), TEM (Transmission Electron Microscopy), DSC (Differential Scanning Calorimetry), BDS (broadband dielectric spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). The results showed that the blends are immiscible, while the diblock copolymers are miscible in the melt state (or very weakly segregated). The PVDF component crystallization was studied in detail. It was found that the polymorphic structure of PVDF was a strong function of its environment. The number of polymorphs and their amount depended on whether it was on its own as a homopolymer, as a block component in the diblock copolymers or as an immiscible phase in the blends. The cooling rate in non-isothermal crystallization or the crystallization temperature in isothermal tests also induced different polymorphic compositions in the PVDF crystals. As a result, we were able to produce samples with exclusive ferroelectric phases at specific preparation conditions, while others with mixtures of paraelectric and ferroelectric phases.

Construction of Natural Loofah/Poly(vinylidene fluoride) Core-Shell Electrospun Nanofibers via a Controllable Janus Nozzle for Switchable Oil-Water Separation.

Developing microstructure and multifunctional membranes toward switchable oil-water separation has been highly desired in oily wastewater treatment. Herein, a controllable Janus nozzle was employed to innovatively electrospin natural loofah/poly(vinylidene fluoride) (PVDF) nanofibers with a core-shell structure for gravity-driven water purification. By adjusting flow rates of the PVDF component, a core-shell structure of the composite fibers was obtained caused by the lower viscosity and surface tension of PVDF. In addition, a steady laminar motion of fluids was constructed based on the Reynolds number of flow fields being less than 2300. In order to investigate the formation mechanism of the microstructure, a series of Janus nozzles with different lengths were controlled to study the blending of the two immiscible components. The gravity difference between the two components might cause disturbance of the jet motion, and the PVDF component unidirectionally encapsulated the loofah to form the shell layer. Most importantly, the dry loofah/PVDF membranes could separate oil from an oil-water mixture, while the water-wetted membrane exhibited switchable separation that could separate water from the mixtures because of the hydroxyl groups of the hydrophilic loofah hydrogen-bonding with water molecules and forming a hydration layer. The composite fibers can be applied in water remediation in practice, and the method to produce core-shell structures seems attractive for technological applications involving macroscopic core-shell nano- or microfibers.

Low temperature mechanical behaviour of PVDF: cryogenic pre-treatment, quasi-static, cyclic and dynamic experimental testing and modelling

PVDF has historically drawn the interest of the scientific community because of its mechanical response to external stimuli. Recently, novel 3D printing techniques have been proposed to manufacture responsive PVDF components, leading to the reconsideration of this polymer in many applications (i.e., sensor-actuator or energy harvesting systems). During manufacturing and/or service conditions, PVDF structures can be subjected to large deformations that, eventually, can involve low temperature loading (e.g., piezoelectric sensors for aircrafts). In this work, a deep mechanical characterisation of PVDF specimens is carried out under low temperature conditions. To this end, we first evaluate potential effects of cryogenic pre-treatment going beyond the glass transition temperature of the polymer. Then, mechanical tests are conducted at different loading conditions and a wide range of testing temperatures from room to temperatures below glass transition: quasi-static compression tests, cyclic loading tests, and high strain rate tests. The complete set of experiments is analysed together to identify slow and fast relaxation mechanisms within the polymeric structure and motivate a new constitutive model. Finally, taking the experimental observations as formulation's basis, a thermodynamically consistent constitutive model is developed for finite deformations. This model describes the mechanical behaviour of PVDF as the combination of slow and fast response and accounts for strain rate dependency, temperature sensitivity, hysteresis and thermal evolution during the deformation process. The results from this work provide a full study of the mechanical behaviour of PVDF at low temperature, considering effects of both pre-treatment and testing temperature, and a new modelling tool to predict its response under a wide range of room-to-low temperature loading conditions.

Assessing the Climate Change Mitigation Potential of Stationary Energy Storage for Electricity Grid Services.

This paper presents a life cycle assessment for three stationary energy storage systems (ESS): lithium iron phosphate (LFP) battery, vanadium redox flow battery (VRFB), and liquid air energy storage (LAES). The global warming potential (GWP) is assessed in relation to uncertainties in usage of the storage, use-phase energy input, cell replacement, and round-trip efficiency parameters. Relative climate change mitigation potential in comparison with equivalent diesel electric and natural gas generation is discussed, as is the effect of recycling at end of life. With variations in input electricity source, recycling, and efficiency, the life cycle global warming potential for LFP ranges from 185 to 440 kg CO2 eq/MWh, for VRFB from 121 to 443 kg CO2 eq/MWh, and for LAES from 48 to 203 kg CO2 eq/MWh. In all cases, there are climate change mitigation benefits compared to fossil fuel alternatives. Use of renewable energy for charging and operation, ease of component recycling/reuse, and reduced parts replacement is shown to reduce GWP. The climate change mitigation potential of ESS for electricity grid operation is further enhanced by increasing use of the storage assets. Recycling of ESS is shown to reduce terrestrial acidification, freshwater eutrophication, and particulate matter impacts. Reduced ozone depletion potential for VRFB and LFP can be achieved by reducing nafion and PVDF components, respectively.

PVDF/PMMA dielectric films with notably decreased dielectric loss and enhanced high‐temperature tolerance

ABSTRACTPolymer dielectrics generally have comparatively low dielectric constant, operating temperatures, and/or high dielectric loss, which limits their uses especially in harsh environment. In this article, a novel trilayered nanocomposite film (TNF) was constructed via solution‐casting and, subsequently, hot‐pressing process, which was composed of two outer layers of polyvinylidene fluoride (PVDF, high dielectric constant) and a middle layer of polymethyl methacrylate (PMMA, high glass transition temperature, Tg). The two outer layers of TNF were filled with barium strontium titanate nanoparticles to further increase the dielectric constant of PVDF. The PMMA in the middle layer was used to largely suppress the dielectric loss and simultaneously improve the temperature tolerance of TNF. Results show that the introduction of PMMA induced oriented crystal formation in the interface regions between PVDF and PMMA components. Moreover, most of the impurity ions were dramatically immobilized by partly oriented α crystals and high Tg PMMA layer until the temperature exceeded 120 °C. Therefore, the TNFs showed a high‐temperature tolerance and notably decreased loss, which are promising for widespread energy storage applications where harsh working conditions are present. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1043–1052

Morphological evaluation and phase behavior of PVDF/PEO blends in the presence of graphene nanoplatelets through rheological measurements

ABSTRACTIn this study, graphene nanoplatelets (GNPs) were incorporated into poly(vinylidene fluoride) (PVDF), poly(ethylene oxide) (PEO), and PVDF/PEO blends using solution casting method in order to achieve binary and ternary polymer nanocomposites. The focus of the work is on the compatibilizing effects of the GNPs on partially miscible PVDF/PEO blends. X‐ray diffraction method, rheological measurements, scanning electron microscopy (SEM), and atomic force microscopy observations enabled us to track the dispersion state and localization of the graphene nanosheets in the nanocomposites. The results exhibited that the nanoplatelets were preferentially distributed through the PVDF phase and/or at the interface of the PVDF/PEO phases. Evaluation of the wetting parameter for the PVDF/PEO/GNPs nanocomposite also verified better affinity of the selected nanofiller with the PVDF component. Extend of the miscibility in the nanocomposites was studied by a well‐known rheological method. A tangible increment in binodal (Tb) and spinodal (Ts) decomposition temperatures by addition of a very low content of the GNPs (0.5 wt %) revealed well‐defined compatibilization effects of the graphene on this binary polymer blend. SEM images at different temperatures confirmed the rheologically determined liquid–liquid phase diagram. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48017.

Preparation and characterization of polyvinylidene fluoride/polysulfone-amide composite nanofiber mats

The polyvinylidene fluoride/polysulfone-amide (PVDF/PSA) composite nanofiber mats were prepared via electrospinning method and characterized systematically by means of scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-Ray diffraction (XRD) and Thermogravimetric analyzer (TGA). In this study, five PVDF/PSA composite spinning solutions with the setting of different mass ratio were mixed by using mechanical agitation method. The mechanical property, wettability and the air permeability of the PVDF/PSA composite nanofiber mats were also measured and discussed. The results show that the addition of PSA has tuned the composite nanofiber mats from hydrophobic to hydrophilic. It is also found that the mechanical property, thermal stability could be improved with the increasing percentage of PVDF component. The PVDF/PSA composite nanofiber mats with the mass ratio of 5/5 gives the best air permeability. In this work, the newly developed composite nanofiber mats have the potential applications in the development of filtration membranes, protective materials, lithium battery diaphragms, etc.

Electrospun Nafion/PVDF single-fiber blended membranes for regenerative H2/Br2 fuel cells

Nafion® perfluorosulfonic acid (PFSA) and poly(vinylidene fluoride) (PVDF) were electrospun simultaneously as a polymer solution mixture using a single needle spinneret. The nanofiber morphology was highly unusual, with bundled 2–5nm fibril strands of Nafion and PVDF aligned along the fiber axis. Membranes were made from fiber mats by a simple hot-pressing step, followed by thermal annealing, where the fibril morphology of Nafion and PVDF in the original nanofibers was retained in the membrane. The PVDF component in the final membrane served three roles, as an electrospinning carrier polymer for PFSA, a mechanical reinforcement, and a hydrophobic (uncharged) component to limit PFSA ionomer swelling. A series of single-fiber membranes with Nafion/PVDF contents ranging from 40/60 to 90/10wt%/wt% were prepared, characterized, and evaluated for use in a regenerative hydrogen/bromine fuel cell. As expected, there was a decrease in proton conductivity, water/electrolyte swelling, and Br2/Br3- permeability with increasing PVDF content. Membrane conductivity was lower than expected based on the weight fraction of PVDF, due presumably to an unusually large fraction of highly structured water. Nevertheless, a single-fiber Nafion/PVDF membrane with a thickness of 18µm and an 80/20wt%/wt% Nafion/PVDF composition performed well in a H2/Br2 regenerative fuel cell due to a combination of low area-specific resistance and low Br2/Br3- crossover. Thus, with an electrolyte containing 0.9M Br2 in 1.0M HBr, the maximum power output was 46% higher than that with a Nafion 212 membrane (1.31 vs. 0.90W/cm2).

Thermal Tensile, and Dynamic Mechanical Properties of PVDF/FKM Blends in Different Curing Systems

Blends of poly(vinylidene fluoride) (PVDF) and fluororubber (FKM) were prepared in an internal mixer by dynamic vulcanization. The effect of FKM, with and without curing system, was studied with respect to the properties of the PVDF/FKM blends. The tensile test showed that the tensile strength and modulus decreased after blending but the elongation-at-break naturally increased because of the presence of rubber in PVDF matrix. The differential scanning calorimetry (DSC) test gave good indications of improved state of miscibility in most blend ratios. The increase of FKM content showed a favorable tendency of PVDF component toward crystallization. The incorporation of FKM as a coblend improved the thermal stability of PVDF, and the temperature at 10% weight loss of the blends increased. This was confirmed by one value of glass transition temperature obtained from DMTA test, which indicated two different values for pure polymers. The rheological tests showed that the complex viscosity and storage modulus of the blends increased with increasing frequency.

Polymorphic Crystallization and Crystalline Reorganization of Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Mixture Influenced by Blending with Poly(vinylidene fluoride).

The effects of poly(vinylidene fluoride) (PVDF) on the crystallization kinetics, competing formations of homocrystallites (HCs) and stereocomplexes (SCs), polymorphic crystalline structure, and HC-to-SC crystalline reorganization of the poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) racemic mixture were investigated. Even though the PLLA/PDLA/PVDF blends are immiscible, blending with PVDF enhances the crystallization rate and SC formation of PLLA/PDLA components at different temperatures that are higher or lower than the melting temperature of the PVDF component; it also facilitates the HC-to-SC melt reorganization upon heating. The crystallization rate and degree of SC crystallinity (Xc,SC) of PLLA/PDLA components in nonisothermal crystallization increase after immiscible blending with PVDF. At different isothermal crystallization temperatures, the crystallization half-time of PLLA/PDLA components decreases; its spherulitic growth rate and Xc,SC increase as the mass fraction of PVDF increases from 0 to 0.5 in the presence of either a solidified or a molten PVDF phase. The HCs formed in primary crystallization of PLLA/PDLA components melt and recrystallize into SCs upon heating; the HC-to-SC melt reorganization is promoted after blending with PVDF. We proposed that the PVDF-promoted crystallization, SC formation, and HC-to-SC melt reorganization of PLLA/PDLA components in PLLA/PDLA/PVDF blends stem from the enhanced diffusion ability of PLLA and PDLA chains.

Critical Composition of the β Form of Poly(vinylidene fluoride) in Miscible Crystalline/Crystalline Blends.

Crystallization and the polymorphic transition of poly(vinylidene fluoride) (PVDF) in its miscible blends with poly(butylene succinate) (PBS) from the melt has been investigated. The presence of a miscible PBS component lowers the crystallization temperature and the melting point of the PVDF component in the blends. It becomes more significant above a critical PBS content between 40 and 50 wt % where PVDF chains are dispersed in the matrix composed by PBS chains. On the other hand, the β form of the PVDF component can be induced at low temperatures, which also has a transition at the critical PBS content.

Carbon nanotubes accelerated poly(vinylidene fluoride) crystallization from miscible poly(vinylidene fluoride)/poly(methyl methacrylate) blend and the resultant crystalline morphologies

A few acidized carbon nanotubes (CNTs) (0.2 and 0.5wt%) were introduced into miscible poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend with a certain weight ratio of 50/50. The dispersion states of CNTs were comparatively investigated using optical microscope, scanning electron microscope and transmission electron microscope. The crystallization behaviors of PVDF component were systematically investigated through different strategies, including nonisothermal crystallization, isothermal crystallization, and the strategy that combined melt-annealing with nonisothermal crystallization. Polarized optical microscope, differential scanning calorimetry and rheometer were used to investigate the crystallization behaviors. The results showed that CNTs exhibited homogeneous dispersion in the PVDF/PMMA/CNT blend composites. The crystallization of PVDF component from miscible PVDF/PMMA blend was greatly accelerated by adding CNTs. Specifically, it was observed for the first time that the two types of spherulites, i.e. ring-banded spherulites and compact spherulites, which were simultaneously induced during the isothermal crystallization process, exhibited different degrees of thermal stability. The latter spherulites exhibited higher thermal stability compared with the former spherulites. The crystallization of PVDF component could be further enhanced after the samples being melt-annealed at high temperatures. It was suggested that the accelerated crystallization of PVDF component from miscible PVDF/PMMA blend was not simply attributed to the nucleation effect of CNTs but possibly attributed to the joint effects of CNT nucleation and inducing phase fluctuation during the crystallization process.

Composition dependent phase transformation of poly(vinylidene fluoride) in its miscible blends upon stretching

This study reports the phase transformation of poly(vinylidene fluoride) (PVDF) in its miscible blends with poly (3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) upon stretching. The original α-form of the PVDF component in the blends is converted into the β-form by stretching, which is decreased with the increasing P34HB content. Moreover, α → β transformation of the PVDF component in the blends exhibits a sharp transition at the P34HB content of about 15 wt%. It is correlated with composition dependent dissolution and crystallization of the P34HB component in the amorphous phase of the PVDF component.

Advanced dielectric polymer nanocomposites by constructing a ternary continuous structure in polymer blends containing poly(methyl methacrylate) (PMMA) modified carbon nanotubes

A nanocomposite with ultra-low percolation threshold and high dielectric performance is prepared by controlling the localization of multiwalled carbon nanotubes (MWNTs) in one phase of a ternary continuous polymer blend system through melt processing. Polystyrene (PS), poly(vinylidene fluoride) (PVDF), and poly(methyl methacrylate) (PMMA) can form a ternary continuous structure when the volume fractions of PS, PVDF and PMMA are 70 vol%, 20 vol%, and 10 vol%, respectively. The PS is a continuous matrix (sea-phase) whereas the other two phases are interconnected threads (the PVDF is situated as the core while the PMMA is the shell, and the thickness of the PMMA shell is about 1 μm). Adding PMMA could improve the compatibility between the PS and PVDF components. Selective distribution of MWNTs in the PMMA shell is achieved through a combination of PMMA modified MWNTs and appropriate processing procedures. The composite shows an ultra-low percolation threshold of ca. 0.3 wt%. When the weight fraction of PMMA modified MWNTs is 0.4 wt%, the dielectric constant of the composite is as high as 182 (at 100 Hz), which is about 60 times higher than that of a pure PS matrix. The composite’s dielectric properties have excellent temperature stability. This approach can provide a new and low-cost route to design high-performance dielectric materials with ultra-low percolation thresholds.

Double-crystalline PLLA-b-PVDF-b-PLLA triblock copolymers: preparation and crystallization

Double-crystalline poly(L-lactide)-block-poly(vinylidene fluoride)-block-poly(L-lactide) (PLLA-b-PVDF-b-PLLA) triblock copolymers were successfully synthesized through ring opening polymerization of L-lactide and benzoyl peroxide initiated polymerization of vinylidene fluoride, followed by copper(I)-catalyzed azide–alkyne coupling of the functionalized PLLA and PVDF. Three triblock copolymers with different block ratios were prepared via this synthetic approach. The block copolymers were miscible in the melt, and an alternating crystalline lamellar nanostructure was formed upon crystallization from the homogeneous melt. Crystallization behavior of the PLLA component depends strongly on the block composition. The crystallization temperature of the lower temperature crystallizing PLLA block increased considerably with respect to its parent homopolymer for rather symmetric block copolymers, indicating a strong nucleation effect, while on the other hand asymmetric block copolymers with low PLLA content demonstrated a large decrease of crystallization temperature, due to a fractionated crystallization process. A confined crystallization mechanism for the PLLA blocks was suggested, indicated by the low degree of crystallization compared to the respective homopolymers, and confirmed by microstructure analysis performed during isothermal crystallization. Contrary to PLLA, crystallization of the higher temperature crystallizing PVDF component within the block copolymer was not influenced by the block composition and similar crystallization behavior was observed with respect to PVDF homopolymers.

Effect of the selective localization of carbon nanotubes in polystyrene/poly(vinylidene fluoride) blends on their dielectric, thermal, and mechanical properties

The selective localization of multiwalled carbon nanotubes (MWNTs) in immiscible polystyrene (PS)/poly(vinylidene fluoride) (PVDF) blends (volume ratio of both components is 1/1) and its effect on composites’ dielectric, thermal, and mechanical properties are systematically studied. Employing two-step mixing process can make MWNTs localize in PS or PVDF phase successfully. When three components are simply mixed together by one-step processing, the MWNTs are selectively distributed in PVDF phase, which is supported by the dielectric measurements and the SEM observations and is consistent with the wetting coefficient evaluation. For the two-step mixing, when the fillers are first mixed with PS in the first step, some of them will migrate into PVDF phase in the second step although the migration is very slow. When the overall volume fraction of MWNTs is 3.9vol%, the selective localization of MWNTs in PVDF phase produces higher dielectric constant (ε′, ca. 485) than the case when the fillers are only in PS phase (ε′ of ca. 16) at 100Hz and room temperature of 25°C. Differential scanning calorimetry (DSC) measurements and mechanical tests show that the selective localization of all the fillers in PVDF phase produces little change of the melting point and crystallinity of PVDF component but slightly higher tensile strength. In contrast to the one-step mixing process, the two-step mixing to selectively localize the fillers in their favorite phase could be used to control the dielectric and mechanical properties of the materials.

Effects of partial replacement of silicone rubber with flurorubber on properties of dynamically cured poly(vinylidene fluoride)/silicone rubber/flurorubber ternary blends

Blends of poly(vinylidene fluoride) (PVDF), silicone rubber (SR) and flurorubber (FKM) were prepared via peroxide dynamic vulcanization. The effect of FKM loading on the morphology, mechanical properties, crystallization behavior, rheology and dynamic mechanical properties of the PVDF/SR/FKM ternary blends was investigated. A “network” was observed in the PVDF/SR binary blends, which disappeared in the ternary blends, but a core-shell-like structure was formed. The mechanical properties were significantly improved. The Izod impact strength of PVDF/SR/FKM blend with 19 wt% FKM was 18.3 kJ/m2, which was 3–4 times higher than the PVDF/SR binary blend. The complex viscosity and storage modulus of the PVDF/SR/FKM blends decreased with increasing FKM content, hence the processability was improved. The increase of FKM content seemed to show a favorable effect on the crystallization of the PVDF component. It promoted the nucleation process of PVDF, leading to increased polymer crystallization rate and higher crystallization temperature. The glass-rubber transition temperature of the PVDF phase moved to a lower temperature.