Preparation of poly(vinylidene fluoride)/poly(methyl methacrylate) membranes by novel electrospinning system for lithium ion batteries

Fibrous membranes of poly(vinylidene fluoride)/poly(methyl methacrylate) (PVdF/PMMA) were fabricated by electrospinning method with different concentrations of polymer solution: 14, 16, and 18 wt %. The morphology of the electrospun membranes was observed by scanning electron microscopy. The images revealed that the nanofibers showed uniform diameter and no bead formation was observed with the concentration of 16 wt %. Also, the structure, crystallinity, ionic conduction, and electrochemical stability of the electrospun membranes were characterized. The results suggested that electrolyte uptake, ionic conduction, and electrochemical stability were improved by the addition of PMMA. Furthermore, with the 16 wt % concentration of the polymer solution, the membrane showed a high ionic conductivity of 3.5 mS cm^?1 at room temperature and electrochemical stability of up to 5.1 V. We predicted that this new method may be very promising for preparing microporous PVdF/PMMA polymer electrolytes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Morphological and infra-red studies on highly oriented poly(vinylidene fluoride)/poly(methyl methacrylate) blends

Highly oriented melt drawn films of poly(vinylidene fluoride) (PVDF) and blends of poly(vinylidene fluoride) and poly(methyl methacrylate) (PMMA) have been studied by transmission electron microscopy, electron diffraction and infra-red spectroscopy. Infra-red spectra show the second moment of the orientation function for PVDF samples to be greater than 0.94. Using such a sample, the transition dipole directions relative to the chain axis have been calculated. Electron microscopic studies of the PVDF/PMMA blends show a transformation for pure PVDF from a lamellar morphology to a mixture of lamellar and needle-like crystals for the 80/20 blend. The 60/40 blend shows a pure needle-like morphology. The β phase content for this blend is dependent upon the composition and thermal history. An increase in the β phase content is observed with the addition of PMMA. After annealing at 110°C, the 50/50 blend shows a lamellar β phase morphology. A significant increase in the segmental orientation of PVDF is also observed.     

Largely restricted nucleation effect of carbon nanotubes in a miscible poly(vinylidene fluoride)/poly(butylene succinate) blend

The crystallization behaviors of miscible poly(vinylidene fluoride)/poly(butylene succinate) (PVDF/PBS) and its blend composites with carbon nanotubes (CNTs) during non‐isothermal and isothermal processes were investigated. The results showed that CNTs acted as heterogeneous nucleation agents and further improved the nucleation ability of PBS and PVDF in blends. However, compared with the nucleation effects of CNTs in PBS/CNT or PVDF/CNT binary composites, the nucleation effect of CNTs in miscible PVDF/PBS was largely restricted and nucleation efficiency was lowered. A reasonable explanation about the restricted nucleation ability of CNTs was studied from the viewpoint of interfacial interactions between polymer components and CNTs, in which a preferential affinity of CNTs to PBS was found. Further combined with the preparation method, it is proposed that PVDF chains adsorbed on the CNT surface in the master batch were peeled off from the CNTs by incorporated PBS chains, due to the better interaction between PBS and CNTs. Finally, the PVDF chains at the interface were diluted by PBS, and most of the CNT surface was covered by PBS chains, giving rise to the nucleation of PBS on the CNTs. On the other hand, unremoved PVDF still adsorbed on the CNT surface and crystallized. Compared with PVDF/CNT and PBS/CNT binary composites, the nucleation density in the ternary composites was greatly lowered, resulting in restricted nucleation effects of CNTs. On the other hand, the preferable adsorption of PBS on CNTs induced an apparent phase fluctuation in the PVDF/PBS blend composites, which also reflected the selective adsorption of PBS on the CNT surface. © 2016 Society of Chemical Industry     

Melt rheology and mechanical crystal transformation in an immiscible blend with poly(vinylidene fluoride) matrix

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.     

Study of carbon black‐filled poly(butylene succinate)/polylactide blend

In this study, carbon black (CB) was used to control the conductivity and the compatibility of immiscible poly(butylene succinate)/polylactide (PBS/PLA) blend. It is shown that most of the CB particles are selectively dispersed in the matrix PBS phase because of the viscosity ratio of the blend components. The increasing viscosity of PBS phase prevents the coalescence of the dispersed PLA domain during the melt mixing. The domain sizes of PLA are refined when compared with that of blank PBS/PLA blend. The ternary composite shows an onset of the electrical conductivity at low filler loadings (1.5 wt %), which is attributed to a percolation of CB in the insulating matrix polymer. Moreover, the composites exhibited remarkable improvement of rheological properties in the melt state when compared with that of blank PBS/PLA blend. According to the van Gurp‐Palmen plot, the rheological percolation threshold for ternary systems is lower than 1.5 wt %. Furthermore, the ternary composites present improved mechanical properties and thermal stability even at very low loading levels of the CB. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study of biodegradable polylactide/poly(butylene carbonate) blend

Polylactide (PLA) was melt blended with poly(butylene carbonate) (PBC) in an effort to improve the toughness of the PLA without compromising its biodegradability and biocompatibility. The miscibility, morphology, thermal behavior, and mechanical properties of the blends were investigated. The blend was an immiscible two‐phase system with PBC uniformly dispersed within the PLA matrix. Because of the interfacial function, the incorporation of PBC accelerated the crystallization rate of PLA. By the incorporation of PBC, a polylatide‐based material with high stiffness and toughness was achieved. Even at 10% of PBC, high elongation at break of 139% was obtained, while the tensile strength remained as high as 50.7 MPa. The Pukanszky model gave credit to modest interfacial adhesion between PLA and PBC although PLA/PBC is an immscible blend. The plastic deformation, occurring via debonding process, is an important energy‐dissipation process and leads to a toughened, biodegradable polymer blend. The important point is that the toughening mechanism requires only modest level of adhesion between particles and the polymer. The molecular mobility is a crucial factor for yield stress and plastic flow. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate)/poly(vinyl pyrrolidone) ternary blends

Ternary blends composed of matrix polymer poly(vinylidene fluoride) (PVDF) with different proportions of poly(methyl methacrylate) (PMMA)/poly(vinyl pyrrolidone) (PVP) blends were prepared by melt mixing. The miscibility, crystallization behavior, mechanical properties and hydrophilicity of the ternary blends have been investigated. The high compatibility of PVDF/PMMA/PVP ternary blends is induced by strong interactions between the carbonyl groups of the PMMA/PVP blend and the CF₂ or CH₂ group of PVDF. According to the Fourier transform infrared and wide‐angle X‐ray difffraction analyses, the introduction of PMMA does not change the crystalline state (i.e. α phase) of PVDF. By contrast, the addition of PVP in the blends favors the transformation of the crystalline state of PVDF from non‐polar α to polar β phase. Moreover, the crystallinity of the PVDF/PMMA/PVP ternary blends also decreases compared with neat PVDF. Through mechanical analysis, the elongation at break of the blends significantly increases to more than six times that of neat PVDF. This confirms that the addition of the PMMA/PVP blend enhances the toughness of PVDF. Besides, the hydrophilicity of PVDF is remarkably improved by blending with PMMA/PVP; in particular when the content of PVP reaches 30 wt%, the water contact angle displays its lowest value which decreased from 91.4° to 51.0°. Copyright © 2011 Society of Chemical Industry     

Interactions in poly(vinylidene fluoride)/poly(methyl methacrylate-co-ethyl methacrylate) blends

Summary The interaction parameters B for blends of poly(vinylidene fluoride) (PVDF) with poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and five methyl methacrylate/ ethyl methacrylate copolymers (PMEMA) were determined by measurements of melting point depression of PVDF. The B values are negative, indicating an attractive intermolecular interaction. The intramolecular interaction parameter between MMA and EMA segments in PMEMA was found to be +3.25 cal/cm³, indicating a repulsive interaction between different monomer segments in the copolymer.     

Properties of mineral filled poly(lactic acid)/poly(methyl methacrylate) blend

This study examines the influence of three different minerals, that is, clay, calcium carbonate, and quartz on the physical, thermal, and mechanical properties of poly(lactic acid) (PLA)/poly(methyl methacrylate) blend. Rheological behavior and phase structure were initially studied by small-amplitude oscillatory shear rheology. Clay- and quartz-filled materials presented an increase in viscosity at low frequency associated with the presence of a yield stress. However, this behavior was not observed for calcium carbonate filled materials due to a matrix degradation effect. To elucidate this aspect, thermal stability and thermal properties were examined by thermogravimetric analysis and differential scanning calorimetry, showing that calcium carbonate promotes degradation of the PLA phase. No nucleating effect was observed in the presence of the minerals. Dynamical mechanical analysis and mechanical characterization revealed an increase of the overall softening temperature and, a reinforcing effect for clay- and quartz-based composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46927.     

Elongational viscosity for miscible and immiscible polymer blends. I. PMMA and AS with similar elongational viscosity

The effects of miscibility and blend ratio on uniaxial elongational viscosity of polymer blends were studied by preparing miscible and immiscible samples at the same composition by using poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-co-styrene) (AS). Miscible polymer blend samples for the elongational viscosity measurement were prepared by using three steps: solvent blends, cast film, and hot press. A phase diagram of blend samples was made by visual observation of cloudiness. Immiscible blend samples were prepared by maintaining the prepared miscible samples at 200°C, which is higher than cloud points using a LCST (lower critical solution temperature) phase diagram. The phase structure of immiscible blends was observed by an optical microscope. The elongational viscosity of all samples was measured at 145°C, which is lower than the cloud-point temperature at all blend ratios. The elongational viscosity of PMMA and AS was similar to each other. The strain-hardening property of miscible blends in the elongational viscosity was only slightly influenced by the blend ratio, and this was also the case with immiscible blends. The strain-hardening property was only slightly influenced, whether it was miscible or immiscible at each blend ratio. Polydispersity in molecular weight for blend samples was not changed by GPC (gel permeation chromatography) analysis. Almost no change in the polydispersity of the molecular weight for blends and the similarity of elongational viscosity between PMMA and AS resulted in little influence of the blend ratio and miscibility on the strain-hardening property. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 757–766, 1999     

Nanophase morphology and crystallization in poly(vinylidene fluoride)/polydimethylsiloxane‐block‐poly(methyl methacrylate) blends

A polydimethylsiloxane‐block‐poly(methyl methacrylate) (PDMS‐b‐PMMA) diblock copolymer was synthesized by the atom transfer radical polymerization method and blended with a high‐molecular‐weight poly(vinylidene fluoride) (PVDF). In this A‐b‐B/C type of diblock copolymer/homopolymer system, semi‐crystallizable PVDF (C) and PMMA (B) block are miscible due to favorable intermolecular interactions. However, the A block (PDMS) is immiscible with PVDF and therefore generates nanostructured morphology via self‐assembly. Crystallization study reveals that both α and γ crystalline phases of PVDF are present in the blends with up to 30 wt% of PDMS‐b‐PMMA block copolymer. Adding 10 wt% of PVDF to PDMS‐b‐PMMA diblock copolymer leads to worm‐like micelle morphology of PDMS of 10 nm in diameter and tens of nanometers in length. Moreover, morphological results show that PDMS nanostructures are localized in the inter‐fibrillar region of PVDF with the addition of up to 20 wt% of the block copolymer. Increase of PVDF long period by 45% and decrease of degree of crystallization by 34% confirm the localization of PDMS in the PVDF inter‐fibrillar region. © 2018 Society of Chemical Industry     

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) copolymer on the properties of polylactide/poly(methyl methacrylate) blend

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) P(S‐co‐GMA) copolymer on the properties of melt blended polylactide/poly(methyl methacrylate) (PLA/PMMA) 80/20 (wt %) composition was studied. In the literature high ductility levels were achieved by melt blending PLA with different additives. However, the gained ductility was counter balanced with drastic drops in strength and modulus values. The novelty of this work was the preparation of PLA‐based blends with polylactide content higher than 75 wt % which showed an impact resistance value improvement of about 60% compared with the neat PLA and maintained similar tensile strength and modulus values as well as glass transition temperature to neat PLA. The addition of only 3 pph of copolymer to PLA/PMMA blend improved the impact resistance almost 100%. The chemical reaction between PLA/PMMA blend and P(S‐co‐GMA) copolymer were analyzed by FTIR, rotational rheometry, and GPC/SEC. Phase structure and morphology were studied by Differential Scanning Calorimetry and Scanning Electronic Microscopy. Tensile and impact properties as well as thermal stability were also studied. Results showed that as the amount of copolymer in the blend was increased then higher was average molecular weight and polydispersity index. After the addition of P(S‐co‐GMA) copolymer to the PLA/PMMA blend the impact resistance, elongation at break and thermal stability were improved while tensile strength and elastic modulus remained almost unaltered. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43935.     

Effect of poly(methyl methacrylate) addition on the dielectric and energy storage properties of poly(vinylidene fluoride)

Poly(methyl methacrylate) (PMMA) was introduced into poly(vinylidene fluoride) (PVDF) via a solution blending process, and a series of PVDF/PMMA blends were obtained in an effort to reduce the energy loss of pure PVDF. The effects of the composition and thermal treatment on the properties of the polymer blends were carefully studied. The results show that the introduction of PMMA led to a lower crystallinity and a smaller crystal size of PVDF for its dilution effect. As a result, the dielectric constant and energy storage density of the polymer blends were slightly reduced. Meanwhile, the phase transition of the PVDF crystals from the α phase to the β phase happened during the quenching of the blend melt to ice–water; this was also observed in the untreated or annealed blends with PMMA contents over 50 wt %. Compared with the α‐PVDF, the PVDF crystals in the β phase possessed a lower melting temperature, a higher dielectric constant, and a lower dielectric loss. The addition of PMMA reduced the energy loss of PVDF significantly, whereas the energy storage density decreased slightly. The optimized blend film with about 40 wt % PMMA and PVDF in the β phase showed a relative high energy storage density and the lowest energy loss. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison of the phase behaviour of the liquid-crystalline polymer/poly(methyl methacrylate) and poly(vinyl acetate)/poly(methyl methacrylate) blends

The phase behaviour of blends of a liquid-crystalline polymer (LCP) and poly(methyl methacrylate) (PMMA), as well as the phase state of blends of PMMA and poly(vinyl acetate) (PVA) has been investigated using light scattering and phase-contrast optical microscopy. The blends of LCP and PMMA have been obtained by coagulation from ternary solutions. The cloud point curves were determined. It was established that both pairs demix upon heating, ie have an LCST. In the region of intermediate composition, the phase separation proceeds according to a spinodal mechanism; however for LCP/PMMA blends, the decomposition proceeds according to a non-linear regime from the very onset. In the region of small amounts of LCP, the phase separation follows a mechanism of nucleation and growth. For PMMA/PVA blends, the spinodal decomposition proceeds according to a linear regime, in spite of the molecular mobility that PVA chains develop at lower temperatures. Only after prolonged heat treatment does the process transit to a non-linear regime. The data show a similarity between the phase behaviour of blends of liquid-crystalline and of flexible amorphous polymers. The distinction consists of the absence of a linear regime of decomposition for LCP-PMMA blends. © 1999 Society of Chemical Industry     

Thermoreversible gelation of poly(vinylidene fluoride)/poly(methyl acrylate) blends in diethyl azelate: a thermodynamic investigation

The thermodynamic behaviour of poly(vinylidene fluoride) (PVF₂)/poly(methyl acrylate) (PMA) blend gels in diethyl azelate (DEAZ) was studied by differential scanning calorimetry at three different blend compositions (x (weight fraction of PVF₂ in the blend) = 0.75, 0.5 and 0.25). Transmission electron microscopy together with optical microscopy indicate the presence of fibrillar network morphology in the gels. The quasi‐binary phase diagrams drawn from both the heating and cooling processes are almost similar, with a hysteresis of 50–60 °C. The possibility of polymer–solvent compound formation in the blend gels have been explored from the composition dependency of enthalpy of gel fusion and enthalpy of gel formation data. Extending the procedure of the pure PVF₂/DEAZ gel systems to blend gels, it has been surmised that polymer–solvent compound formation also occurs in blend gels, but the stoichiometry of the complexes varies with blend composition. The shapes of the quasi‐binary phase diagrams of the blend gels are different in some cases from that of pure PVF₂/DEAZ, gel indicating that the polymer–solvent compounds are incongruent or singular type depending on the blend compositions. A possible explanation for this behaviour has been offered from entropic and enthalpic viewpoints. Copyright © 2003 Society of Chemical Industry     

Piezo- and pyroelectricity in polymer blends of poly(vinylidene fluoride)/poly(methyl methacrylate)

Compatible polymer blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) can be used as suitable model systems for investigating the relationship between the physico-chemical structure of polymers and their piezo- and pyroelectric activity. The structure of PVDF/PMMA blends can be varied over a very wide range which can lead to a strong influence on the piezo- and pyroelectric activity and the corresponding coefficients d₃₁ and g₃. The values of d₃₁ and g₃ were found to vary over nearly five decades whereas the normalized coefficients $\text{d}{}_{31}\text{P}$ and $\text{g}{}_3\text{P}$ remain largely unaffected. This emphasizes the importance of the molecular processes causing the macroscopic polarization P during the poling procedure. For a given polarization P and a given temperature T the properties of the polymer matrix, however, are far less important for the values obtained for d₃₁ and g₃. The experimental results were compared with theoretical predictions based on models which were recently developed by Tashiro et al., Broadhurst et al. and by Mopsik et al.. Considering the appropriate scope of each model a good agreement between theory and experiment is observed and general contradictions have not been found.     

Hydrolytic stability of polylactide and poly(methyl methacrylate) blends

The hydrolytic stability of polylactide/poly(methyl methacrylate) (PLA/PMMA) blends prepared using a twin‐screw extrusion process was investigated. The effects of hydrolysis were monitored in neutral and alkaline media at 80 °C by tracking the changes in molecular weight distribution, weight loss, water uptake, and crystallization behavior. The crystallinity of PLA in blends prior to hydrolysis was shown to be largely hindered by the presence of PMMA. However, PLA recrystallized rapidly during hydrolysis. The PMMA in the blends was shown to provide increased hydrolytic and structural stability to the blends. In the neutral medium, the presence of PMMA delayed and reduced the weight loss but did not significantly affect PLA degradation kinetics. On the other hand, in the alkaline medium, the weight loss rate was strongly decreased in presence of PMMA and the kinetics of degradation was shown to be depend on PMMA content. The microstructure of these blends throughout the hydrolysis process was also examined by scanning electron microscopy. A porous structure, with interconnected pores in the 20–50 nm range, was developed due to the selective removal of PLA. Based on these morphological observations, erosion mechanism of PLA/PMMA blends was discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45991.     

Solution and solid‐state NMR investigation of poly(methyl methacrylate)/poly(vinyl pyrrolidone) blends

The development of polymer blends has become very important for the polymer industry because these blends have shown to be a successful and versatile alternative way to obtain a new polymer. In this study, binary blends formed by poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) were prepared by solution casting and evaluated by solution and solid‐state NMR. Variations in the microstructure of PMMA were analyzed by ¹³C solution NMR. Solid‐state NMR promotes responses on physical interaction, homogeneity, and compatibility to use these blends to understand the behavior of the ternary blends. The NMR results led‐us to acquire information on the polymer blend microstructure and molecular dynamic behavior. From the NMR solution, it was possible to evaluate the microstructure of both polymer blend components; they were atactic. From the solid state, good compatibility between both polymer components was characterized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 372–377, 2004     

Radiational hardening of poly(vinylidene fluoride)–poly(methyl methacrylate)–polystyrene ternary blends

Specimens of poly(vinylidene fluoride) (PVDF)–poly(methyl methacrylate) (PMMA)–polystyrene (PS) polyblends with different weight percentage ratios of the three polymers were prepared with the solution cast technique. The effect of γ irradiation on the Vicker's microhardness was studied. Among the three pure polymers, PVDF, PMMA, and PS, the γ irradiation imparted crosslinking in PVDF, thereby causing radiational hardening. In the cases of PMMA and PS, the effect of irradiation exhibited a predominance of both the scissioning and crosslinking processes in different ranges of doses. Moreover, at a dose of 5 Mrad, in both PMMA and PS, maximum radiational crosslinking was observed. The effect of γ irradiation seemed to stabilize beyond 15 Mrad in PVDF and beyond 20 Mrad in PMMA and PS. Microhardness measurements on ternary blends of PVDF, PMMA, and PS revealed that the blend with low contents of PMMA, that is, up to 5 wt %, yielded softening, whereas increasing the content of PMMA beyond 5 wt % produced a hardened material because of radiational crosslinking, and a higher content of PMMA in the blend facilitated this crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3107–3111, 2004     

Poly(vinylidene fluoride) - poly(methyl methacrylate) blends

A dynamic mechanical study of four blends of PVdF and PMMA plus the constituent homopolymers indicates that these two polymers are partly compatible, but that a crystalline PVdF phase also exists. The pure PVdF sample showed four transitions at ?95°, ?25° 75° and 100°C which are ascribed to a restricted chain motion of the Schatzki type, to a crystalline phase transition, to the glass transition and to premelting of poorly formed crystallites respectively. A longitudinal sonic velocity versus composition plot is interpreted in terms of the overall morphology of the blends whilst differential scanning calorimetry measurements are used to study crystalline melting.